Mechanism of action of myosin X, a membrane-associated molecular motor |
| |
Authors: | Kovács Mihály Wang Fei Sellers James R |
| |
Institution: | Laboratory of Molecular Physiology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892-1762, USA. kovacsm@mail.nih.gov |
| |
Abstract: | We have performed a detailed biochemical kinetic and spectroscopic study on a recombinant myosin X head construct to establish a quantitative model of the enzymatic mechanism of this membrane-bound myosin. Our model shows that during steady-state ATP hydrolysis, myosin X exhibits a duty ratio (i.e. the fraction of the cycle time spent strongly bound to actin) of around 16%, but most of the remaining myosin heads are also actin-attached even at moderate actin concentrations in the so-called "weak" actin-binding states. Contrary to the high duty ratio motors myosin V and VI, the ADP release rate constant from actomyosin X is around five times greater than the maximal steady-state ATPase activity, and the kinetic partitioning between different weak actin-binding states is a major contributor to the rate limitation of the enzymatic cycle. Two different ADP states of myosin X are populated in the absence of actin, one of which shows very similar kinetic properties to actomyosin.ADP. The nucleotide-free complex of myosin X with actin shows unique spectral and biochemical characteristics, indicating a special mode of actomyosin interaction. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|