UMMS Affiliation

Department of Cell Biology; Department of Physiology

Publication Date

5-23-2008

Document Type

Article

Subjects

Actins; Adenosine Triphosphatases; Animals; *Gene Expression Regulation; Image Processing, Computer-Assisted; Microscopy, Electron; Models, Biological; Molecular Conformation; Muscle, Skeletal; Myosin Heavy Chains; Myosins; Pectinidae; Phosphorylation; Protein Binding; Protein Structure, Tertiary

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Intramolecular interaction between myosin heads, blocking key sites involved in actin-binding and ATPase activity, appears to be a critical mechanism for switching off vertebrate smooth-muscle myosin molecules, leading to relaxation. We have tested the hypothesis that this interaction is a general mechanism for switching off myosin II-based motile activity in both muscle and nonmuscle cells. Electron microscopic images of negatively stained myosin II molecules were analyzed by single particle image processing. Molecules from invertebrate striated muscles with phosphorylation-dependent regulation showed head-head interactions in the off-state similar to those in vertebrate smooth muscle. A similar structure was observed in nonmuscle myosin II (also phosphorylation-regulated). Surprisingly, myosins from vertebrate skeletal and cardiac muscle, which are not intrinsically regulated, undergo similar head-head interactions in relaxing conditions. In all of these myosins, we also observe conserved interactions between the 'blocked' myosin head and the myosin tail, which may contribute to the switched-off state. These results suggest that intramolecular head-head and head-tail interactions are a general mechanism both for inducing muscle relaxation and for switching off myosin II-based motile activity in nonmuscle cells. These interactions are broken when myosin is activated.

Rights and Permissions

Citation: Mol Biol Cell. 2008 Aug;19(8):3234-42. Epub 2008 May 21. Link to article on publisher's site

DOI of Published Version

10.1091/mbc.E08-02-0206

Related Resources

Link to Article in PubMed

Journal/Book/Conference Title

Molecular biology of the cell

PubMed ID

18495867

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