Abstract
Correction: Head-Head Interactions of Resting Myosin Crossbridges in Intact Frog Skeletal Muscles, Revealed by Synchrotron X-Ray Fiber Diffraction
Highlights
Muscles relax when the interaction between actin and myosin is blocked by molecular switches on either or both the thin and the thick filaments in a sarcomere which is the smallest functional and structural unit of striated muscle
Myosin filaments in smooth muscles and certain types of invertebrate striated muscles participate in the regulation of muscle contraction, the role of thick filament structure in the regulation of striated muscles of higher vertebrates, which are primarily controlled by Ca2+-binding to troponin-tropomyosin on the thin filaments, has not been clearly elucidated
Using an atomic structure of myosin molecule, these studies have revealed the structure of thick filaments to nanometer-scale resolution, suggesting that interactions between myosin heads resulting in the formation of a so-called ‘‘interacting head motif’’ are responsible for switching off the myosin molecules in vertebrate smooth muscles [3], invertebrate striated muscles with phosphorylation-dependent regulation such as tarantula [4,5] and limulus [6] muscles and in scallop muscles [7] with Ca2+dependent regulation
Summary
Muscles relax when the interaction between actin and myosin is blocked by molecular switches on either or both the thin and the thick filaments in a sarcomere which is the smallest functional and structural unit of striated muscle. Recent studies showed that similar head-head interactions of myosin crossbridges occurred in isolated thick filaments from vertebrate fish skeletal [8] and cardiac striated [9,10] muscles and in heavy meromyosin (HMM) molecules (comprising of the two heads and part of the rod) from vertebrate cardiac and skeletal muscles when they were treated with blebbistatin, a known inhibitor of actin-binding and ATPase (catalysis of the hydrolysis of adenosine triphosphate (ATP)) activity of myosin molecules, those muscles are not thought to be intrinsically regulated by the myosin molecules [11] This interacting head structure is a plausible model for relaxation based on isolated myosin filaments, it has not been clearly proved whether or not this structure occurs in the native myosin filaments in higher vertebrate muscles
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