Article Abstract:
Nucleotides cause small conformational changes, which are probably converted by the light-chain domain into large movements, in the motor domain of smooth muscles. Myosin II crossbridges release products of ATP hydrolysis on reaction with F-actin. The release of ATP involves an articulation of the myosin head on actin and small movements of the light-chain. There are major conformational changes in the light-chain domain when the myosin head reacts with F-actin in the presence and absence of MgADP, though the changes in the motor domain are slight.
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Article Abstract:
Rat liver myosin-I of relative molecular mass 130,000 and chick intestinal brush-border myosin-I, two members of the myosin-I family, produce a working stroke that takes place in two phases. Research in this area has used an optical-tweezers transducer to measure the mechanical transitions made by a single myosin head while it is attached to actin. It is likely that the two phases are linked to different biochemical states of the actomyosin cycle. It has been established that the slower myosins have longer working strokes.
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Article Abstract:
A 32 degree swing occurs in the light-chain-binding domain of the brush border myosin I (BBMI)-decorated actin filaments, on ADP release. The heavy chains, however, remain steady. The myosin, from intestinal microvilli, has a heavy chain and three calmodulin light chains. A description of the three-dimensional maps of BBMI actin filaments with and without bound MgADP is given. The movement is similar to that observed in myosin II but the magnitude of the change is different.
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