Interaction Between Two Myosin Heads in Acto-Smooth Muscle Heavy Meromyosin Rigor Complex
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Muscle contraction occurs as a result of the cyclic interaction between actin and myosin, coupled with the hydrolysis of ATP by the myosin heads1). A myosin molecule consists of two globular heads and a rod-shaped tail2). It is thought that each myosin head functions as a contractile machinery unit, because each head shows ATPase activity and binds to F-actin. A still unsolved question is whether or not the two heads of a myosin molecule interact with each other during their cyclic interaction with F-actin. Here we report that when chicken gizzard heavy meromyosin (HMM) in its rigor complex with F-actin is reacted with the zero-length cross-linker l-ethyl-3-[3-(dimethylamino)propyl] carbodiimide (EDC), the two heads of the HMM molecule are cross-linked. This result suggests that the two heads of smooth muscle myosin are in contact with each other when myosin is attached to F-actin. It is thus possible that the two myosin heads interact with each other when cross-bridges are formed.
KeywordsMyosin Head Cyanogen Bromide Myosin Molecule Heavy Meromyosin Cyclic Interaction
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