Array ( [0] => {{Short description|Superfamily of motor proteins}} [1] => {{Use dmy dates|date=April 2022}} [2] => {{cs1 config|name-list-style=vanc|display-authors=6}} [3] => [[File:Myosine.gif|thumb|Part of the myosin II structure. Atoms in the heavy chain are colored pink (on the left-hand side); atoms in the light chains are colored faded-orange and faded-yellow (also on the left-hand side).]] [4] => '''Myosins''' ({{IPAc-en|ˈ|m|aɪ|ə|s|ᵻ|n|,_|-|oʊ|-}}{{refn|{{MerriamWebsterDictionary|Myosin}}}}{{refn|{{cite web |url=https://www.oxforddictionaries.com/definition/english/myosin |archive-url=https://web.archive.org/web/20120824023230/http://oxforddictionaries.com/definition/english/myosin |url-status=dead |archive-date=24 August 2012 |title=myosin - definition of myosin in English from the Oxford dictionary |publisher=[[OxfordDictionaries.com]] |access-date=2016-01-20 }} }}) are a [[Protein superfamily|superfamily]] of [[motor protein]]s best known for their roles in [[muscle contraction]] and in a wide range of other [[motility]] processes in [[eukaryote]]s. They are [[adenosine triphosphate|ATP]]-dependent and responsible for [[actin]]-based motility. [5] => [6] => The first myosin (M2) to be discovered was in 1864 by [[Wilhelm Kühne]]. Kühne had extracted a viscous protein from [[skeletal muscle]] that he held responsible for keeping the tension state in muscle. He called this protein ''myosin''.{{cite journal | vauthors = Hartman MA, Spudich JA | title = The myosin superfamily at a glance | journal = Journal of Cell Science | volume = 125 | issue = Pt 7 | pages = 1627–1632 | date = April 2012 | pmid = 22566666 | pmc = 3346823 | doi = 10.1242/jcs.094300 }}{{cite journal | vauthors = Szent-Györgyi AG | title = The early history of the biochemistry of muscle contraction | journal = The Journal of General Physiology | volume = 123 | issue = 6 | pages = 631–641 | date = June 2004 | pmid = 15173217 | pmc = 2234565 | doi = 10.1085/jgp.200409091 }} The term has been extended to include a group of similar [[ATPase]]s found in the [[cell (biology)|cells]] of both [[striated muscle tissue]] and [[smooth muscle tissue]]. [7] => [8] => Following the discovery in 1973 of enzymes with myosin-like function in ''[[Acanthamoeba|Acanthamoeba castellanii]]'', a global range of divergent myosin [[gene]]s have been discovered throughout the realm of eukaryotes.{{cite journal | vauthors = Pollard TD, Korn ED | title = Acanthamoeba myosin. I. Isolation from Acanthamoeba castellanii of an enzyme similar to muscle myosin | journal = The Journal of Biological Chemistry | volume = 248 | issue = 13 | pages = 4682–4690 | date = July 1973 | pmid = 4268863 | doi = 10.1016/S0021-9258(19)43718-6 | url = http://www.jbc.org/content/248/13/4682.abstract | url-status = live | doi-access = free | archive-url = https://web.archive.org/web/20160106171718/http://www.jbc.org/content/248/13/4682.abstract | archive-date = 2016-01-06 }} [9] => [10] => Although myosin was originally thought to be restricted to [[muscle cell]]s (hence ''[[wikt:myo-#Prefix|myo-]]''(s) + ''[[wikt:-in#Suffix|-in]]''), there is no single "myosin"; rather it is a very large superfamily of genes whose protein products share the basic properties of actin binding, ATP [[hydrolysis]] (ATPase enzyme activity), and force transduction. Virtually all eukaryotic cells contain myosin [[protein isoform|isoforms]]. Some isoforms have specialized functions in certain cell types (such as muscle), while other isoforms are ubiquitous. The structure and function of myosin is globally conserved across species, to the extent that rabbit muscle myosin II will bind to actin from an [[amoeba]].McMahon, T. A. 1984. Muscles, Reflexes and Locomotion. 1st Edition. Princeton University Press. {{ISBN|978-0-691-02376-2}} [11] => [12] => {{TOC limit|limit=3}} [13] => [14] => == Structure and functions == [15] => [16] => ===Domains=== [17] => Most myosin molecules are composed of a [[Myosin head|head]], neck, and tail domain. [18] => * The ''[[Myosin head|head domain]]'' binds the filamentous [[actin]], and uses [[Adenosine triphosphate|ATP]] [[hydrolysis]] to generate force and to "walk" along the filament towards the barbed (+) end (with the exception of myosin VI, which moves towards the pointed (-) end). [19] => * the ''neck domain'' acts as a linker and as a lever arm for transducing force generated by the catalytic motor domain. The neck domain can also serve as a binding site for [[Myosin light chain|myosin ''light chains'']] which are distinct proteins that form part of a [[macromolecule|macromolecular]] complex and generally have regulatory functions. [20] => * The ''tail domain'' generally mediates interaction with cargo molecules and/or other myosin [[protein subunits|subunit]]s. In some cases, the tail domain may play a role in regulating motor activity. [21] => [22] => ===Power stroke=== [23] => {{Main|Muscle contraction}} [24] => [25] => Multiple [[myosin-2|myosin II]] molecules generate force in [[muscle contraction|skeletal muscle]] through a power stroke mechanism fuelled by the energy released from ATP hydrolysis.{{cite journal | vauthors = Tyska MJ, Warshaw DM | title = The myosin power stroke | journal = Cell Motility and the Cytoskeleton | volume = 51 | issue = 1 | pages = 1–15 | date = January 2002 | pmid = 11810692 | doi = 10.1002/cm.10014 }} The power stroke occurs at the release of phosphate from the myosin molecule after the ATP hydrolysis while myosin is tightly bound to actin. The effect of this release is a conformational change in the molecule that pulls against the actin. The release of the ADP molecule leads to the so-called rigor state of myosin.{{cite journal | vauthors = von der Ecken J, Heissler SM, Pathan-Chhatbar S, Manstein DJ, Raunser S | title = Cryo-EM structure of a human cytoplasmic actomyosin complex at near-atomic resolution | journal = Nature | volume = 534 | issue = 7609 | pages = 724–728 | date = June 2016 | pmid = 27324845 | doi = 10.1038/nature18295 | s2cid = 4472407 | bibcode = 2016Natur.534..724E }} The binding of a new ATP molecule will release myosin from actin. ATP hydrolysis within the myosin will cause it to bind to actin again to repeat the cycle. The combined effect of the myriad power strokes causes the muscle to contract. [26] => [27] => == Nomenclature, evolution, and the family tree == [28] => [[File:MyosinUnrootedTree.jpg|thumb|right|upright=2.2|Myosin unrooted [[phylogenetic tree]]]] [29] => [30] => The wide variety of myosin genes found throughout the eukaryotic phyla were named according to different schemes as they were discovered. The nomenclature can therefore be somewhat confusing when attempting to compare the functions of myosin proteins within and between organisms. [31] => [32] => Skeletal muscle myosin, the most conspicuous of the myosin superfamily due to its abundance in [[muscle fibers]], was the first to be discovered. This protein makes up part of the [[sarcomere]] and forms macromolecular filaments composed of multiple myosin subunits. Similar filament-forming myosin proteins were found in [[cardiac muscle]], smooth muscle, and nonmuscle cells. However, beginning in the 1970s, researchers began to discover new myosin genes in simple eukaryotes encoding proteins that acted as monomers and were therefore entitled Class I myosins. These new myosins were collectively termed "unconventional myosins"{{cite journal | vauthors = Cheney RE, Mooseker MS | title = Unconventional myosins | journal = Current Opinion in Cell Biology | volume = 4 | issue = 1 | pages = 27–35 | date = February 1992 | pmid = 1558751 | doi = 10.1016/0955-0674(92)90055-H }} and have been found in many tissues other than muscle. These new superfamily members have been grouped according to phylogenetic relationships derived from a comparison of the amino acid sequences of their head domains, with each class being assigned a [[Roman numeral]]{{cite journal | vauthors = Cheney RE, Riley MA, Mooseker MS | title = Phylogenetic analysis of the myosin superfamily | journal = Cell Motility and the Cytoskeleton | volume = 24 | issue = 4 | pages = 215–223 | year = 1993 | pmid = 8477454 | doi = 10.1002/cm.970240402 }}{{cite journal | vauthors = Goodson HV | title = Molecular evolution of the myosin superfamily: application of phylogenetic techniques to cell biological questions | journal = Society of General Physiologists Series | volume = 49 | pages = 141–157 | year = 1994 | pmid = 7939893 }}{{cite journal | vauthors = Hodge T, Cope MJ | title = A myosin family tree | journal = Journal of Cell Science | volume = 113 | issue = 19 | pages = 3353–3354 | date = October 2000 | pmid = 10984423 | doi = 10.1242/jcs.113.19.3353 }}{{cite journal | vauthors = Berg JS, Powell BC, Cheney RE | title = A millennial myosin census | journal = Molecular Biology of the Cell | volume = 12 | issue = 4 | pages = 780–794 | date = April 2001 | pmid = 11294886 | pmc = 32266 | doi = 10.1091/mbc.12.4.780 }} (see phylogenetic tree). The unconventional myosins also have divergent tail domains, suggesting unique functions.{{cite journal | vauthors = Oliver TN, Berg JS, Cheney RE | title = Tails of unconventional myosins | journal = Cellular and Molecular Life Sciences | volume = 56 | issue = 3-4 | pages = 243–257 | date = October 1999 | pmid = 11212352 | doi = 10.1007/s000180050426 | s2cid = 23407921 }} The now diverse array of myosins likely evolved from an ancestral [[wiktionary:Precursor|precursor]] (see picture). [33] => [34] => Analysis of the amino acid sequences of different myosins shows great variability among the tail domains, but strong conservation of head domain sequences. Presumably this is so the myosins may interact, via their tails, with a large number of different cargoes, while the goal in each case – to move along actin filaments – remains the same and therefore requires the same machinery in the motor. For example, the [[human genome]] contains over 40 different myosin [[genes]]. [35] => [36] => These differences in shape also determine the speed at which myosins can move along actin filaments. The hydrolysis of ATP and the subsequent release of the [[phosphate]] group causes the "power stroke", in which the "lever arm" or "neck" region of the heavy chain is dragged forward. Since the power stroke always moves the lever arm by the same angle, the length of the lever arm determines the displacement of the cargo relative to the actin filament. A longer lever arm will cause the cargo to traverse a greater distance even though the lever arm undergoes the same angular displacement – just as a person with longer legs can move farther with each individual step. The velocity of a myosin motor depends upon the rate at which it passes through a complete kinetic cycle of ATP binding to the release of ADP. [37] => [38] => ===Myosin classes=== [39] => [40] => ====Myosin I==== [41] => Myosin I, a ubiquitous cellular protein, functions as monomer and functions in [[Vesicle (biology)|vesicle]] transport.{{cite web | vauthors = Maciver S |title=Myosin I | url= http://www.bms.ed.ac.uk/research/others/smaciver/Myosin%20I.htm |date= 4 June 2003 |access-date=2007-05-23 |url-status=dead |archive-url=https://web.archive.org/web/20070602100321/http://www.bms.ed.ac.uk/research/others/smaciver/Myosin%20I.htm |archive-date= 2 June 2007 }} It has a step size of 10 nm and has been implicated as being responsible for the adaptation response of the stereocilia in the inner ear.{{cite journal | vauthors = Batters C, Arthur CP, Lin A, Porter J, Geeves MA, Milligan RA, Molloy JE, Coluccio LM | title = Myo1c is designed for the adaptation response in the inner ear | journal = The EMBO Journal | volume = 23 | issue = 7 | pages = 1433–1440 | date = April 2004 | pmid = 15014434 | pmc = 391074 | doi = 10.1038/sj.emboj.7600169 }} [42] => [43] => ====Myosin II==== [44] => [[File:Sarcomere.svg|thumb|350px|[[Sliding filament model]] of muscle contraction.]] [45] => [[File:Cardiac sarcomere structure.png|thumb|351x351px|Cardiac sarcomere structure featuring myosin]] [46] => [[Myosin-2|Myosin II]] (also known as conventional myosin) is the myosin type responsible for producing [[muscle contraction]] in [[muscle cell]]s in most animal cell types. It is also found in non-muscle cells in contractile bundles called [[stress fiber]]s.{{cite journal | vauthors = Vicente-Manzanares M, Ma X, Adelstein RS, Horwitz AR | title = Non-muscle myosin II takes centre stage in cell adhesion and migration | journal = Nature Reviews. Molecular Cell Biology | volume = 10 | issue = 11 | pages = 778–790 | date = November 2009 | pmid = 19851336 | pmc = 2834236 | doi = 10.1038/nrm2786 }} [47] => [48] => * Myosin II contains two ''heavy chains'', each about 2000 [[amino acids]] in length, which constitute the head and tail domains. Each of these heavy chains contains the [[N-terminus|N-terminal]] head domain, while the [[C-terminus|C-terminal]] tails take on a [[coiled-coil]] morphology, holding the two heavy chains together (imagine two snakes wrapped around each other, as in a [[caduceus]]). Thus, myosin II has two heads. The intermediate ''neck'' domain is the region creating the angle between the head and tail.{{cite journal | vauthors = Aguilar HN, Mitchell BF | title = Physiological pathways and molecular mechanisms regulating uterine contractility | journal = Human Reproduction Update | volume = 16 | issue = 6 | pages = 725–744 | year = 2010 | pmid = 20551073 | doi = 10.1093/humupd/dmq016 | doi-access = free }} In smooth muscle, a single gene (''[[MYH11]]''){{cite journal | vauthors = Matsuoka R, Yoshida MC, Furutani Y, Imamura S, Kanda N, Yanagisawa M, Masaki T, Takao A | title = Human smooth muscle myosin heavy chain gene mapped to chromosomal region 16q12 | journal = American Journal of Medical Genetics | volume = 46 | issue = 1 | pages = 61–67 | date = April 1993 | pmid = 7684189 | doi = 10.1002/ajmg.1320460110 }}) codes for the heavy chains myosin II, but [[Alternative splicing|splice variants]] of this gene result in four distinct isoforms. [49] => * It also contains 4 [[myosin light chain]]s (MLC), resulting in 2 per head, weighing 20 (MLC20) and 17 (MLC17) [[kilodalton|kDa]]. These bind the heavy chains in the "neck" region between the head and tail. [50] => **[[File:MyosinII AU to rel.gif|thumb|Self-inhibition of Myosin II.{{cite journal | vauthors = Pettersen EF, Goddard TD, Huang CC, Couch GS, Greenblatt DM, Meng EC, Ferrin TE | title = UCSF Chimera--a visualization system for exploratory research and analysis | journal = Journal of Computational Chemistry | volume = 25 | issue = 13 | pages = 1605–1612 | date = October 2004 | pmid = 15264254 | doi = 10.1002/jcc.20084 }}{{cite journal | vauthors = Yang S, Tiwari P, Lee KH, Sato O, Ikebe M, Padrón R, Craig R | title = Cryo-EM structure of the inhibited (10S) form of myosin II | journal = Nature | volume = 588 | issue = 7838 | pages = 521–525 | date = December 2020 | pmid = 33268893 | pmc = 7746622 | doi = 10.1038/s41586-020-3007-0 }}{{cite journal | vauthors = Milton DL, Schneck AN, Ziech DA, Ba M, Facemyer KC, Halayko AJ, Baker JE, Gerthoffer WT, Cremo CR | title = Direct evidence for functional smooth muscle myosin II in the 10S self-inhibited monomeric conformation in airway smooth muscle cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 4 | pages = 1421–1426 | date = January 2011 | pmid = 21205888 | pmc = 3029703 | doi = 10.1073/pnas.1011784108 }} The movie begins with Myosin II in the 10S conformation with a folded tail domain, the blocked head and free head.{{cite journal | vauthors = Yang S, Tiwari P, Lee KH, Sato O, Ikebe M, Padrón R, Craig R | title = Cryo-EM structure of the inhibited (10S) form of myosin II | journal = Nature | volume = 588 | issue = 7838 | pages = 521–525 | date = December 2020 | pmid = 33268893 | pmc = 7746622 | doi = 10.1038/s41586-020-3007-0 }}{{cite journal | vauthors = Yang S, Lee KH, Woodhead JL, Sato O, Ikebe M, Craig R | title = The central role of the tail in switching off 10S myosin II activity | journal = The Journal of General Physiology | volume = 151 | issue = 9 | pages = 1081–1093 | date = September 2019 | pmid = 31387899 | pmc = 6719407 | doi = 10.1085/jgp.201912431 }} The movie schematically depicts tail unfolding and the resulting active 6S confirmation followed by tail folding back to the 10S conformation.{{cite journal | vauthors = Yang S, Tiwari P, Lee KH, Sato O, Ikebe M, Padrón R, Craig R | title = Cryo-EM structure of the inhibited (10S) form of myosin II | journal = Nature | volume = 588 | issue = 7838 | pages = 521–525 | date = December 2020 | pmid = 33268893 | pmc = 7746622 | doi = 10.1038/s41586-020-3007-0 }}{{cite journal | vauthors = Yang S, Lee KH, Woodhead JL, Sato O, Ikebe M, Craig R | title = The central role of the tail in switching off 10S myosin II activity | journal = The Journal of General Physiology | volume = 151 | issue = 9 | pages = 1081–1093 | date = September 2019 | pmid = 31387899 | pmc = 6719407 | doi = 10.1085/jgp.201912431 }} The illustration is conceptual: transitory states and diffusive motions associated with folding/unfolding are not shown.{{cite journal | vauthors = Milton DL, Schneck AN, Ziech DA, Ba M, Facemyer KC, Halayko AJ, Baker JE, Gerthoffer WT, Cremo CR | title = Direct evidence for functional smooth muscle myosin II in the 10S self-inhibited monomeric conformation in airway smooth muscle cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 4 | pages = 1421–1426 | date = January 2011 | pmid = 21205888 | pmc = 3029703 | doi = 10.1073/pnas.1011784108 }}]]The MLC20 is also known as the ''regulatory light chain'' and actively participates in [[muscle contraction]]. [51] => **The MLC17 is also known as the ''essential light chain''. Its exact function is unclear, but is believed to contribute to the structural stability of the myosin head along with MLC20. Two variants of MLC17 (MLC17a/b) exist as a result of [[alternative splicing]] at the MLC17 gene. [52] => [53] => In muscle cells, the long [[coiled-coil]] tails of the individual myosin molecules can auto-inhibit active function in the 10S conformation or upon phosphorylation, change to the 6S conformation and join, forming the thick filaments of the [[sarcomere]].{{cite journal | vauthors = Yang S, Lee KH, Woodhead JL, Sato O, Ikebe M, Craig R | title = The central role of the tail in switching off 10S myosin II activity | journal = The Journal of General Physiology | volume = 151 | issue = 9 | pages = 1081–1093 | date = September 2019 | pmid = 31387899 | pmc = 6719407 | doi = 10.1085/jgp.201912431 }}{{cite journal | vauthors = Milton DL, Schneck AN, Ziech DA, Ba M, Facemyer KC, Halayko AJ, Baker JE, Gerthoffer WT, Cremo CR | title = Direct evidence for functional smooth muscle myosin II in the 10S self-inhibited monomeric conformation in airway smooth muscle cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 108 | issue = 4 | pages = 1421–1426 | date = January 2011 | pmid = 21205888 | pmc = 3029703 | doi = 10.1073/pnas.1011784108 }} The force-producing head domains stick out from the side of the thick filament, ready to walk along the adjacent actin-based thin filaments in response to the proper chemical signals and may be in either auto-inhibited or active conformation. The balance/transition between active and inactive states is subject to extensive chemical regulation. [54] => {{Further|Muscle contraction}} [55] => {{Further|Meromyosin}} [56] => [57] => ====Myosin III==== [58] => Myosin III is a poorly understood member of the myosin family. It has been studied ''[[in vivo]]'' in the eyes of ''[[Drosophila]]'', where it is thought to play a role in [[phototransduction]].{{cite web |url=http://www.bms.ed.ac.uk/research/others/smaciver/Myosin%20III.htm |title=New Page 2 |access-date=2015-12-16 |url-status=live |archive-url=https://web.archive.org/web/20090707074536/http://www.bms.ed.ac.uk/research/others/smaciver/Myosin%20III.htm |archive-date=2009-07-07 }} A human [[Homology (biology)|homologue]] gene for myosin III, [[MYO3A]], has been uncovered through the [[Human Genome Project]] and is expressed in the [[retina]] and [[cochlea]].{{EntrezGene|53904}}[[File:Myosin V.png|thumbnail|right|Crystal structure of myosin V motor with essential light chain – nucleotide-free]] [59] => ====Myosin IV==== [60] => Myosin IV has a single [[IQ motif]] and a tail that lacks any coiled-coil forming sequence. It has homology similar to the tail domains of Myosin VII and XV.{{cite journal | vauthors = Sellers JR | title = Myosins: a diverse superfamily | journal = Biochimica et Biophysica Acta | volume = 1496 | issue = 1 | pages = 3–22 | date = March 2000 | pmid = 10722873 | doi = 10.1016/S0167-4889(00)00005-7 | doi-access = free }} [61] => [62] => ====Myosin V==== [63] => Myosin V is an unconventional myosin motor, which is processive as a [[Dimer (chemistry)|dimer]] and has a step size of 36 nm.{{cite journal | vauthors = Warshaw DM | title = Tilting and twirling as myosin V steps along actin filaments as detected by fluorescence polarization | journal = The Journal of General Physiology | volume = 139 | issue = 2 | pages = 97–100 | date = February 2012 | pmid = 22291143 | pmc = 3269787 | doi = 10.1085/jgp.201210769 }} It translocates (walks) along actin filaments traveling towards the barbed end (+ end) of the filaments. Myosin V is involved in the transport of cargo (e.g. RNA, vesicles, organelles, mitochondria) from the center of the cell to the periphery, but has been furthermore shown to act like a dynamic tether, retaining vesicles and organelles in the actin-rich periphery of cells.{{cite journal | vauthors = Lecuona E, Minin A, Trejo HE, Chen J, Comellas AP, Sun H, Grillo D, Nekrasova OE, Welch LC, Szleifer I, Gelfand VI, Sznajder JI | title = Myosin-Va restrains the trafficking of Na+/K+-ATPase-containing vesicles in alveolar epithelial cells | journal = Journal of Cell Science | volume = 122 | issue = Pt 21 | pages = 3915–3922 | date = November 2009 | pmid = 19808891 | pmc = 2773192 | doi = 10.1242/jcs.046953 }}{{cite journal | vauthors = Hammer JA, Sellers JR | title = Walking to work: roles for class V myosins as cargo transporters | journal = Nature Reviews. Molecular Cell Biology | volume = 13 | issue = 1 | pages = 13–26 | date = December 2011 | pmid = 22146746 | doi = 10.1038/nrm3248 | s2cid = 11853457 }} A recent single molecule in vitro reconstitution study on assembling actin filaments suggests that Myosin V travels farther on newly assembling (ADP-Pi rich) F-actin, while processive runlengths are shorter on older (ADP-rich) F-actin.{{cite journal | vauthors = Zimmermann D, Santos A, Kovar DR, Rock RS | title = Actin age orchestrates myosin-5 and myosin-6 run lengths | journal = Current Biology | volume = 25 | issue = 15 | pages = 2057–2062 | date = August 2015 | pmid = 26190073 | pmc = 4556227 | doi = 10.1016/j.cub.2015.06.033 }} [64] => [[File:Image animated.gif|thumb|A ribbon diagram of the Myosin V molecular motor pseudo-colored to illustrate major subdomains. In the interest of visual clarity, important loops (which are often labeled separately in the literature) are not singled out. This perspective highlights the nucleotide-binding site and the separation of the U50 and L50 subdomains which form the actin-binding site cleft.]] [65] => The Myosin V motor head can be subdivided into the following functional regions:{{cite journal | vauthors = Sweeney HL, Houdusse A | title = Structural and functional insights into the Myosin motor mechanism | journal = Annual Review of Biophysics | volume = 39 | issue = 1 | pages = 539–557 | date = 2010-04-01 | pmid = 20192767 | doi = 10.1146/annurev.biophys.050708.133751 }} [66] => [67] => * [[Nucleotide]]-binding site - These elements together coordinate di-valent metal cations (usually [[magnesium]]) and catalyze hydrolysis: [68] => ** Switch I - This contains a highly conserved SSR motif. Isomerizes in the presence of [[Adenosine triphosphate|ATP]]. [69] => ** Switch II - This is the Kinase-GTPase version of the [[Walker B motif]] DxxG. Isomerizes in the presence of ATP. [70] => ** P-loop - This contains the [[Walker A motif]] GxxxxGK(S,T). This is the primary ATP binding site. [71] => [72] => * Transducer - The seven [[Β strands|β-strands]] that underpin the motor head's structure.{{cite journal | vauthors = Kull FJ, Vale RD, Fletterick RJ | title = The case for a common ancestor: kinesin and myosin motor proteins and G proteins | journal = Journal of Muscle Research and Cell Motility | volume = 19 | issue = 8 | pages = 877–886 | date = November 1998 | pmid = 10047987 | doi = 10.1023/a:1005489907021 | s2cid = 25508217 }} [73] => * U50 and L50 - The Upper (U50) and Lower (L50) domains are each around 50[[kDa]]. Their spatial separation{{cite journal | vauthors = Sasaki N, Ohkura R, Sutoh K | title = Insertion or deletion of a single residue in the strut sequence of Dictyostelium myosin II abolishes strong binding to actin | language = English | journal = The Journal of Biological Chemistry | volume = 275 | issue = 49 | pages = 38705–38709 | date = December 2000 | pmid = 11005804 | doi = 10.1074/jbc.M001966200 | doi-access = free }} forms a cleft critical for binding to [[Actin-binding protein|actin]] and some regulatory compounds. [74] => * SH1 helix and Relay - These elements together provide an essential mechanism for coupling the enzymatic state of the motor domain to the powerstroke-producing region (converter domain, lever arm, and light chains).{{cite journal | vauthors = Shibata K, Koyama T, Inde S, Iwai S, Chaen S | title = Mutations in the SH1 helix alter the thermal properties of myosin II | journal = Biophysics and Physicobiology | volume = 14 | pages = 67–73 | date = 2017 | pmid = 28630813 | pmc = 5468464 | doi = 10.2142/biophysico.14.0_67 }}{{cite journal | vauthors = Kodera N, Ando T | title = The path to visualization of walking myosin V by high-speed atomic force microscopy | journal = Biophysical Reviews | volume = 6 | issue = 3-4 | pages = 237–260 | date = 2014-06-18 | pmid = 25505494 | pmc = 4256461 | doi = 10.1007/s12551-014-0141-7 }} [75] => * Converter - This converts a change of conformation in the motor head to an angular displacement of the lever arm (in most cases reinforced with light chains). [76] => [77] => ====Myosin VI==== [78] => [[File:MyosinVI 2V26.png|thumb|State of myosin VI from PDB 2V26 before the power stroke {{cite journal | vauthors = Ménétrey J, Llinas P, Mukherjea M, Sweeney HL, Houdusse A | title = The structural basis for the large powerstroke of myosin VI | journal = Cell | volume = 131 | issue = 2 | pages = 300–308 | date = October 2007 | pmid = 17956731 | doi = 10.1016/j.cell.2007.08.027 | s2cid = 14102005 | doi-access = free }}]] [79] => [80] => Myosin VI is an unconventional myosin motor, which is primarily processive as a dimer, but also acts as a nonprocessive monomer. It walks along actin filaments, travelling towards the pointed end (- end) of the filaments.{{cite journal | vauthors = Buss F, Kendrick-Jones J | title = How are the cellular functions of myosin VI regulated within the cell? | journal = Biochemical and Biophysical Research Communications | volume = 369 | issue = 1 | pages = 165–175 | date = April 2008 | pmid = 18068125 | pmc = 2635068 | doi = 10.1016/j.bbrc.2007.11.150 }} Myosin VI is thought to transport [[endocytic cycle|endocytic]] vesicles into the cell.{{cite journal | vauthors = Buss F, Spudich G, Kendrick-Jones J | title = Myosin VI: cellular functions and motor properties | journal = Annual Review of Cell and Developmental Biology | volume = 20 | pages = 649–676 | year = 2004 | pmid = 15473855 | pmc = 1693462 | doi = 10.1146/annurev.cellbio.20.012103.094243 }} [81] => [82] => ====Myosin VII==== [83] => Myosin VII is an unconventional myosin with two [[FERM domain]]s in the tail region. It has an extended lever arm consisting of five calmodulin binding IQ motifs followed by a single alpha helix (SAH){{cite journal | vauthors = Li J, Chen Y, Deng Y, Unarta IC, Lu Q, Huang X, Zhang M | title = Ca2+-Induced Rigidity Change of the Myosin VIIa IQ Motif-Single α Helix Lever Arm Extension | journal = Structure | volume = 25 | issue = 4 | pages = 579–591.e4 | date = April 2017 | pmid = 28262393 | doi = 10.1016/j.str.2017.02.002 | doi-access = free }} Myosin VII is required for [[phagocytosis]] in ''[[Dictyostelium discoideum]]'', [[spermatogenesis]] in ''[[Caenorhabditis elegans|C. elegans]]'' and [[stereocilia]] formation in mice and zebrafish.{{cite book |title=Molecular Motors | veditors = Schliwa M |publisher=Wiley-VCH |year=2003 |pages=516, 518 |isbn=978-3-527-30594-0}} [84] => [85] => ====Myosin VIII==== [86] => Myosin VIII is a plant-specific myosin linked to cell division;{{cite journal | vauthors = Reddy AS, Day IS | title = Analysis of the myosins encoded in the recently completed Arabidopsis thaliana genome sequence | journal = Genome Biology | volume = 2 | issue = 7 | pages = RESEARCH0024 | year = 2001 | pmid = 11516337 | pmc = 55321 | doi = 10.1186/gb-2001-2-7-research0024 | doi-access = free }} specifically, it is involved in regulating the flow of cytoplasm between cells{{cite journal | vauthors = Baluska F, Cvrcková F, Kendrick-Jones J, Volkmann D | title = Sink plasmodesmata as gateways for phloem unloading. Myosin VIII and calreticulin as molecular determinants of sink strength? | journal = Plant Physiology | volume = 126 | issue = 1 | pages = 39–46 | date = May 2001 | pmid = 11351069 | pmc = 1540107 | doi = 10.1104/pp.126.1.39 }} and in the localization of vesicles to the [[phragmoplast]].{{cite journal | vauthors = Reichelt S, Knight AE, Hodge TP, Baluska F, Samaj J, Volkmann D, Kendrick-Jones J | title = Characterization of the unconventional myosin VIII in plant cells and its localization at the post-cytokinetic cell wall | journal = The Plant Journal | volume = 19 | issue = 5 | pages = 555–567 | date = September 1999 | pmid = 10504577 | doi = 10.1046/j.1365-313X.1999.00553.x | doi-access = free }} [87] => [88] => ====Myosin IX==== [89] => Myosin IX is a group of single-headed motor proteins. It was first shown to be minus-end directed,{{cite journal | vauthors = Inoue A, Saito J, Ikebe R, Ikebe M | title = Myosin IXb is a single-headed minus-end-directed processive motor | journal = Nature Cell Biology | volume = 4 | issue = 4 | pages = 302–306 | date = April 2002 | pmid = 11901422 | doi = 10.1038/ncb774 | s2cid = 12158370 }} but a later study showed that it is plus-end directed.{{cite journal | vauthors = O'Connell CB, Mooseker MS | title = Native Myosin-IXb is a plus-, not a minus-end-directed motor | journal = Nature Cell Biology | volume = 5 | issue = 2 | pages = 171–172 | date = February 2003 | pmid = 12563277 | doi = 10.1038/ncb924 | s2cid = 687308 }} The movement mechanism for this myosin is poorly understood. [90] => [91] => ====Myosin X==== [92] => Myosin X is an unconventional myosin motor, which is functional as a [[Dimer (chemistry)|dimer]]. The dimerization of myosin X is thought to be antiparallel.{{cite journal | vauthors = Lu Q, Ye F, Wei Z, Wen Z, Zhang M | title = Antiparallel coiled-coil-mediated dimerization of myosin X | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 109 | issue = 43 | pages = 17388–17393 | date = October 2012 | pmid = 23012428 | pmc = 3491486 | doi = 10.1073/pnas.1208642109 | doi-access = free }} This behavior has not been observed in other myosins. In mammalian cells, the motor is found to localize to [[filopodia]]. Myosin X walks towards the barbed ends of filaments. Some research suggests it preferentially walks on bundles of actin, rather than single filaments.{{cite journal | vauthors = Ropars V, Yang Z, Isabet T, Blanc F, Zhou K, Lin T, Liu X, Hissier P, Samazan F, Amigues B, Yang ED, Park H, Pylypenko O, Cecchini M, Sindelar CV, Sweeney HL, Houdusse A | title = The myosin X motor is optimized for movement on actin bundles | journal = Nature Communications | volume = 7 | pages = 12456 | date = September 2016 | pmid = 27580874 | pmc = 5025751 | doi = 10.1038/ncomms12456 | bibcode = 2016NatCo...712456R }} It is the first myosin motor found to exhibit this behavior. [93] => [94] => ====Myosin XI==== [95] => Myosin XI directs the movement of organelles such as [[plastids]] and [[mitochondria]] in plant cells.{{cite journal | vauthors = Sattarzadeh A, Krahmer J, Germain AD, Hanson MR | title = A myosin XI tail domain homologous to the yeast myosin vacuole-binding domain interacts with plastids and stromules in Nicotiana benthamiana | journal = Molecular Plant | volume = 2 | issue = 6 | pages = 1351–1358 | date = November 2009 | pmid = 19995734 | doi = 10.1093/mp/ssp094 | doi-access = free }} It is responsible for the light-directed movement of [[chloroplasts]] according to light intensity and the formation of [[stromule]]s interconnecting different plastids. Myosin XI also plays a key role in polar root tip growth and is necessary for proper [[root hair]] elongation.{{cite journal | vauthors = Peremyslov VV, Prokhnevsky AI, Avisar D, Dolja VV | title = Two class XI myosins function in organelle trafficking and root hair development in Arabidopsis | journal = Plant Physiology | volume = 146 | issue = 3 | pages = 1109–1116 | date = March 2008 | pmid = 18178669 | pmc = 2259062 | doi = 10.1104/pp.107.113654 }} A specific Myosin XI found in ''[[Nicotiana tabacum]]'' was discovered to be the fastest known processive [[molecular motor]], moving at 7μm/s in 35 nm steps along the [[actin]] filament.{{cite journal | vauthors = Tominaga M, Kojima H, Yokota E, Orii H, Nakamori R, Katayama E, Anson M, Shimmen T, Oiwa K | title = Higher plant myosin XI moves processively on actin with 35 nm steps at high velocity | journal = The EMBO Journal | volume = 22 | issue = 6 | pages = 1263–1272 | date = March 2003 | pmid = 12628919 | pmc = 151065 | doi = 10.1093/emboj/cdg130 }} [96] => [97] => ====Myosin XII==== [98] => [99] => ====Myosin XIII==== [100] => [101] => ====Myosin XIV==== [102] => This myosin group has been found in the [[Apicomplexa]] phylum.{{cite journal | vauthors = Delbac F, Sänger A, Neuhaus EM, Stratmann R, Ajioka JW, Toursel C, Herm-Götz A, Tomavo S, Soldati T, Soldati D | title = Toxoplasma gondii myosins B/C: one gene, two tails, two localizations, and a role in parasite division | journal = The Journal of Cell Biology | volume = 155 | issue = 4 | pages = 613–623 | date = November 2001 | pmid = 11706051 | pmc = 2198869 | doi = 10.1083/jcb.200012116 }} The myosins localize to plasma membranes of the intracellular [[parasitism|parasites]] and may then be involved in the cell invasion process.{{cite journal | vauthors = Hettmann C, Herm A, Geiter A, Frank B, Schwarz E, Soldati T, Soldati D | title = A dibasic motif in the tail of a class XIV apicomplexan myosin is an essential determinant of plasma membrane localization | journal = Molecular Biology of the Cell | volume = 11 | issue = 4 | pages = 1385–1400 | date = April 2000 | pmid = 10749937 | pmc = 14854 | doi = 10.1091/mbc.11.4.1385 }} [103] => [104] => This myosin is also found in the ciliated protozoan ''Tetrahymena thermaphila''. Known functions include: transporting phagosomes to the nucleus and perturbing the developmentally regulated elimination of the macronucleus during conjugation. [105] => [106] => ====Myosin XV==== [107] => Myosin XV is necessary for the development of the actin core structure of the non-motile [[stereocilia]] located in the inner ear. It is thought to be functional as a monomer. [108] => [109] => ====Myosin XVI==== [110] => [111] => ====Myosin XVII==== [112] => [113] => ====Myosin XVIII==== [114] => MYO18A A gene on chromosome 17q11.2 that encodes actin-based motor molecules with ATPase activity, which may be involved in maintaining stromal cell scaffolding required for maintaining intercellular contact. [115] => [116] => ====Myosin XIX==== [117] => Unconventional myosin XIX (Myo19) is a mitochondrial associated myosin motor.{{cite web |title=MYO19 - Unconventional myosin-XIX - Homo sapiens (Human) - MYO19 gene & protein |url=https://www.uniprot.org/uniprot/Q96H55 |website=www.uniprot.org |access-date=21 April 2022 |language=en}} [118] => [119] => ==Genes in humans== [120] => Note that not all of these genes are active. [121] => [122] => * Class I: [[MYO1A]], [[MYO1B]], [[MYO1C]], [[MYO1D]], [[MYO1E]], [[MYO1F]], [[MYO1G]], [[MYO1H]] [123] => * Class II: [[MYH1]], [[MYH2]], [[MYH3]], [[MYH4]], [[MYH6]], [[MYH7]], [[MYH7B]], [[MYH8]], [[MYH9]], [[MYH10]], [[MYH11]], [[MYH13]], [[MYH14]], [[MYH15]], [[MYH16]] [124] => * Class III: [[MYO3A]], [[MYO3B]] [125] => * Class V: [[MYO5A]], [[MYO5B]], [[MYO5C]] [126] => * Class VI: [[MYO6]] [127] => * Class VII: [[MYO7A]], [[MYO7B]] [128] => * Class IX: [[MYO9A]], [[MYO9B]] [129] => * Class X: [[MYO10]] [130] => * Class XV: [[MYO15A]] [131] => * Class XVI: [[MYO16]] [132] => * Class XVIII: [[MYO18A]], [[MYO18B]] [133] => * Class XIX: [[MYO19]] [134] => [135] => Myosin light chains are distinct and have their own properties. They are not considered "myosins" but are components of the macromolecular complexes that make up the functional myosin enzymes. [136] => * Light chain: [[MYL1]], [[MYL2]], [[MYL3]], [[MYL4]], [[MYL5]], [[MYL6]], [[MYL6B]], [[MYL7]], [[MYL9]], [[MYLIP]], [[MYLK]], [[MYLK2]], [[MYLL1]] [137] => [138] => ==Paramyosin== [139] => Paramyosin is a large, 93-115kDa [[muscle]] [[protein]] that has been described in a number of diverse [[invertebrate]] phyla.{{cite journal | vauthors = Winkelman L | title = Comparative studies of paramyosins | journal = Comparative Biochemistry and Physiology. B, Comparative Biochemistry | volume = 55 | issue = 3B | pages = 391–397 | year = 1976 | pmid = 987889 | doi = 10.1016/0305-0491(76)90310-2 }} Invertebrate thick filaments are thought to be composed of an inner paramyosin core surrounded by myosin. The myosin interacts with [[actin]], resulting in fibre contraction.{{cite journal | vauthors = Twarog BM | title = Aspects of smooth muscle function in molluscan catch muscle | journal = Physiological Reviews | volume = 56 | issue = 4 | pages = 829–838 | date = October 1976 | pmid = 185635 | doi = 10.1152/physrev.1976.56.4.829 }} Paramyosin is found in many different invertebrate species, for example, [[Brachiopoda]], [[Sipunculidea]], [[Nematoda]], [[Annelida]], [[Mollusca]], [[Arachnida]], and [[Insecta]]. Paramyosin is responsible for the "catch" mechanism that enables sustained contraction of muscles with very little energy expenditure, such that a [[clam]] can remain closed for extended periods. [140] => [141] => Paramyosins can be found in seafood. A recent computational study showed that following human intestinal digestion, paramyosins of [[common octopus]], [[Humboldt squid]], Japanese abalone, Japanese scallop, [[Mediterranean mussel]], [[Pacific oyster]], [[sea cucumber]], and [[Whiteleg shrimp]] could release short [[Peptide|peptides]] that inhibit the enzymatic activities of [[ACE inhibitor|angiotensin converting enzyme]] and [[Dipeptidyl peptidase-4 inhibitor|dipeptidyl peptidase]].{{cite journal | vauthors = Chai TT, Wong CC, Sabri MZ, Wong FC | title = Seafood Paramyosins as Sources of Anti-Angiotensin-Converting-Enzyme and Anti-Dipeptidyl-Peptidase Peptides after Gastrointestinal Digestion: A Cheminformatic Investigation | journal = Molecules | volume = 27 | issue = 12 | page = 3864 | date = June 2022 | pmid = 35744987 | pmc = 9229108 | doi = 10.3390/molecules27123864 | doi-access = free }} [142] => [143] => == References == [144] => {{reflist}} [145] => [146] => == Further reading == [147] => {{refbegin}} [148] => * {{cite book | vauthors = Gavin RH |title=A Survey of Cell Biology |volume=206 |pages=97–134 |year=2001 |doi=10.1016/S0074-7696(01)06020-X |chapter=Myosins in protists |series=International Review of Cytology |pmid=11407764 |isbn=978-0-12-364610-1}} [149] => * {{cite journal | vauthors = Mooseker MS, Cheney RE | title = Unconventional myosins | journal = Annual Review of Cell and Developmental Biology | volume = 11 | pages = 633–675 | year = 1995 | pmid = 8689571 | doi = 10.1146/annurev.cb.11.110195.003221 }} [150] => * {{cite journal | vauthors = Sellers JR | title = Myosins: a diverse superfamily | journal = Biochimica et Biophysica Acta | volume = 1496 | issue = 1 | pages = 3–22 | date = March 2000 | pmid = 10722873 | doi = 10.1016/S0167-4889(00)00005-7 | doi-access = free }} [151] => * {{cite journal | vauthors = Soldati T, Geissler H, Schwarz EC | title = How many is enough? Exploring the myosin repertoire in the model eukaryote Dictyostelium discoideum | journal = Cell Biochemistry and Biophysics | volume = 30 | issue = 3 | pages = 389–411 | year = 1999 | pmid = 10403058 | doi = 10.1007/BF02738121 | s2cid = 13319819 }} [152] => *Molecular Biology of the Cell. Alberts, Johnson, Lewis, Raff, Roberts, and Walter. 4th Edition. 949–952. [153] => {{refend}} [154] => [155] => ==Additional images== [156] => [157] => Image:Querbrückenzyklus 1.png|Phase 1 [158] => Image:Querbrückenzyklus 2.png|Phase 2 [159] => Image:Querbrückenzyklus 3.png|Phase 3 [160] => Image:Querbrückenzyklus 4.png|Phase 4 [161] => [162] => [163] => == External links == [164] => {{Commons category|Myosins}} [165] => *[http://www.mechanobio.info/modules/go-0003774#2_go-0003774 MBInfo – Myosin Isoforms] [166] => *[http://www.mechanobio.info/modules/go-0008570#2_go-0008570 MBInfo – The Myosin Powerstroke] [167] => *[http://www.banyantree.org/jsale/actinmyosin/index.html Myosin Video] A video of a moving myosin motor protein. [168] => *{{MeshName|Myosins}} [169] => *[https://wayback.archive-it.org/all/20090924163125/http://www.mrc-lmb.cam.ac.uk/myosin/myosin.html The Myosin Homepage] [170] => *http://cellimages.ascb.org/cdm4/item_viewer.php?CISOROOT=/p4041coll12&CISOPTR=101&CISOBOX=1&REC=2{{dead link|date=November 2010}} Animation of a moving myosin motor protein [171] => *{{EC number|3.6.4.1}} [172] => *[http://www.pdbe.org/emsearch/myosin* 3D macromolecular structures of myosin from the EM Data Bank(EMDB)] [173] => [174] => {{Cytoskeletal Proteins}} [175] => {{ATPases}} [176] => {{Muscle tissue}} [177] => [178] => [[Category:Motor proteins]] [179] => [[Category:Cytoskeleton proteins]] [180] => [[Category:Protein superfamilies]] [181] => [[Category:Skeletal muscle]] [] => )
good wiki

Myosin

Myosins are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility.

More about us

About

Expert Team

Vivamus eget neque lacus. Pellentesque egauris ex.

Award winning agency

Lorem ipsum, dolor sit amet consectetur elitorceat .

10 Year Exp.

Pellen tesque eget, mauris lorem iupsum neque lacus.

You might be interested in

Actin

Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils.

ATPase

ATPases ( Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or the inverse reaction.

Eukaryote

Eukaryotes are complex organisms whose cells contain a nucleus and other membrane-bound organelles.

Gene

Gene is a widely recognized online encyclopedia that provides information on a wide range of topics, including biology, genetics, and other related fields.

Macromolecule

A macromolecule is a large molecule typically composed of smaller subunits called monomers.

Mitochondria

Nucleotide

A nucleotide is a basic structural unit of DNA and RNA.

Protein

Proteins are macromolecules found in all living organisms.

Retina

The retina is a layer of tissue that lines the inner surface of the eye.