myosin


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Related to myosin: Myosin light chain kinase

myosin

(mī`əsĭn), one of the two major proteinprotein,
any of the group of highly complex organic compounds found in all living cells and comprising the most abundant class of all biological molecules. Protein comprises approximately 50% of cellular dry weight.
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 constituents responsible for contraction of muscle. In muscle cells myosin is arranged in long filaments called thick filaments that lie parallel to the microfilaments of actinactin,
a protein abundantly present in many cells, especially muscle cells, that significantly contributes to the cell's structure and motility. Actin can very quickly assemble into long polymer rods called microfilaments.
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. In muscle contraction, filaments of actin alternately chemically link and unlink with those of myosin in a creeping or sliding action. The energy for this reaction is supplied by adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
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. Myosin and actin also function in the motility of diverse non-muscle cells. In slime moldsslime mold
or slime fungus,
a heterotrophic organism once regarded as a fungus but later classified with the Protista. In a recent system of classification based on analysis of nucleic acid (genetic material) sequences, slime molds have been classified in a major group
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, for example, although present in much smaller quantities and forming shorter filaments, the interaction of the two proteins is employed to change cell shape and permit some movements.

Myosin

 

a fibrillar protein, a basic component of contractile muscle fibers (myofibrils); it constitutes 40–60 percent of the total muscle protein content. Myosin combines with another myofibrillar protein, actin, to form actomyosin, a primary structural element in the contractile muscular system. Another important property of myosin is its ability to split adenosine triphosphate (ATP) (V. A. Engel’gardt and M. N. Liubimova, 1939). Owing to the ATP-ase activity of myosin, the chemical energy of the high-energy ATP bonds is transformed into the mechanical energy necessary for muscular contraction. Myosin has a molecular weight of approximately 500,000. When acted upon by proteolytic enzymes, myosin decomposes into heavy meromyosin and light meromyosin (approximate molecular weights, 350,000 and 150,000, respectively).

Electron photomicrographs of myosin molecules reveal a bacilliform structure (1,600 × 25 angstroms), with two globular formations at one end. It is conjectured that the two polypeptide chains which make up the myosin molecule are twisted into a spiral. Proteins that are similar to myosin have been discovered in flagella, cilia, and other motile structures in many species of protozoa and bacteria, as well as in the spermatozoids of animals and certain plants.

REFERENCES

Poglazov, B. F. Struktura i funktsii sokratitel’nykh belkov. Moscow, 1965.
Finean, J R Rialagicheskie ul’$$$ Moacow, 1970. (Translated from English.)

V. O. SHPIKITER

myosin

[′mī·ə·sən]
(biochemistry)
A muscle protein, comprising up to 50% of the total muscle proteins; combines with actin to form actomycin.
References in periodicals archive ?
The early increase in G' indicated that the preliminary elastic protein network structure, which was mainly due to the unfolding and denaturation of myosin heads [37].
Huff-Lonergan, "Myosin light chain 1 release from myofibrillar fraction during postmortem aging is a potential indicator of proteolysis and tenderness of beef," Meat Science, vol.
Naoki et al., "Dynamic regulation of myosin light chain phosphorylation by rhokinase," PLoS One, vol.
Egelhoff, "Keratin 5-Cre-driven excision of nonmuscle myosin IIA in early embryo trophectoderm leads to placenta defects and embryonic lethality," Developmental Biology, vol.
[128] examined whether the immune tolerance to swine cardiac myosin could protect BALB/c mice that have myosin-induced myocarditis from myocardial injury.
Our finding revealed that the variants p.A1324D and p.Q1337Qfs*22 are located at myosin XVA motor domain.
Conservation within the myosin motor domain: implications for structure and function.
Because the fluorescence is detected at a different wavelength from the excitation light, only fluorescently marked molecules are monitored at the exclusion of other molecules, which means one can observe isolated myosin molecules by labeling them with a fluorescent probe.
It has been reported that myosin is implicated in endothelial barrier signaling [56].
In lamellum, myosin II forms bipolar filaments and those filaments together with actin filaments generate a contractile force in lamellum [18].
Desorbed protein from 2-hour-oxidized samples exhibited greater losses of fluorescence and more extensive polymerization of myosin than myofibrillar protein in the continuous phase, as detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis.