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This Sandbox is Reserved from 13/03/2012, through 01/06/2012 for use in the course "Proteins and Molecular Mechanisms" taught by Robert B. Rose at the North Carolina State University, Raleigh, NC USA. This reservation includes Sandbox Reserved 451 through Sandbox Reserved 500.
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Myosin is comprised of 35 different classes of motor proteins, and is universal in all eukaryotic cells.[1] It acts in complex with actin to create a powerstroke and cause muscular contraction and relaxation.[2]

2mys ribbon-diagram

Drag the structure with the mouse to rotate

Contents

Structure

Oligomeric State

Secondary Structure

Active Site

The actin-binding, catalytic site of myosin is known as S1 (subfragment 1). This is the amino-terminal globular head portion of the myosin molecule. The S1 head is divided into three subdomains: the NH2-terminal 25 kDa region, a central 50 kDa region, and the COOH-terminal 20 kDa region. Further analysis of the S1 active site of myosin suggests that the γ-phosphate (of ATP) binds near the apex of the 50 kDa cleft. It is believed to be a region critical to function, because of the presence of evolutionarily conserved residues along the central cleft.[2]

Ligands

X-Ray Crystallography

[3]

It was not until recently that crystal structures could be used to analyze myosin and it's role in the actinomysin chemomechanical cycle.

Mechanism of Action

Myosin plays a role in the universal mechanism known as the actinomysin chemomechanical cycle. Actin binds and releases myosin, causing the myosin lever to interact and relax in a cyclic manner.[1]

  1. ATP binds to S1 causing Actin to disassociate out of it's rigor complex (between actin and the S1 catalytic site on myosin)
  2. S1 causes the hydolysis of ATP to ADP and Pi
  3. Actin interacts with the S1-ADP-Pi complex and Pi is released
  4. S1 catalytic site's affinity for actin increases and the Actin-S1-ADP forms
  5. ADP is released, causing actin and myosin to again enter into the tightly bound rigor complex[2]

Medical Implications or Possible Applications

References

  1. ↑ 1.0 1.1 Varkuti BH, Yang Z, Kintses B, Erdelyi P, Bardos-Nagy I, Kovacs AL, Hari P, Kellermayer M, Vellai T, Malnasi-Csizmadia A. A novel actin binding site of myosin required for effective muscle contraction. Nat Struct Mol Biol. 2012 Feb 12;19(3):299-306. doi: 10.1038/nsmb.2216. PMID:22343723 doi:10.1038/nsmb.2216
  2. ↑ 2.0 2.1 2.2 Ruppel KM, Spudich JA. Structure-function studies of the myosin motor domain: importance of the 50-kDa cleft. Mol Biol Cell. 1996 Jul;7(7):1123-36. PMID:8862525
  3. ↑ Koubassova NA, Tsaturyan AK. Molecular mechanism of actin-myosin motor in muscle. Biochemistry (Mosc). 2011 Dec;76(13):1484-506. doi: 10.1134/S0006297911130086. PMID:22339600 doi:10.1134/S0006297911130086
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