Actin-Myosin Biochemistry and Structure
The energy which drives contracting muscle comes from the hydrolysis of ATP, in which the terminal phosphate group is detached by a water molecule. How this energy is transducted into tension and movement can be revealed by studying actin-myosin-ATP interactions in solution. In 1971, Lymn and Taylor showed that the binding of myosin to actin, the subsequent working stroke, and detachment from actin all proceed after the myosin-ATP complex has been hydrolysed, so the hydrolysis reaction merely reprimes the myosin motor for another cycle of interaction. Our current understanding of the biochemical actomyosinATPase cycle comes from a mixture of solution biochemistry and the atomic structure of myosin-nucleotide complexes, which address some key questions. Can ATP also be hydrolysed by actomyosin? How is the timing of the working stroke related to the release of the products of hydrolysis (ADP and inorganic Pi) on bound myosin? How much energy is released in each transition of the cycle? And is just one ATP hydrolysed per one cycle of attachment and detachment? Answers to these questions provide the bedrock for quantitative models of the biochemical cycle in active muscle.
KeywordsATP cycling Actomyosin Hydrolysis Product release Atomic structures
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