期刊
JOURNAL OF CELL BIOLOGY
卷 155, 期 4, 页码 625-635出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200103128
关键词
myosin V; in vitro motility; laser trap; single molecule; mechanics
类别
资金
- NHLBI NIH HHS [R01 HL038113, HL38113] Funding Source: Medline
- NIAMS NIH HHS [AR47906, P01 AR047906] Funding Source: Medline
- NIGMS NIH HHS [GM208343, F32 GM020384] Funding Source: Medline
Myosin V is a double-headed unconventional myosin that has been implicated in organelle transport. To perform this role, myosin V may have a high duty cycle. To test this hypothesis and understand the properties of this molecule at the molecular level, we used the laser trap and in vitro motility assay to characterize the mechanics of heavy meromyosin-like fragments of myosin V (M5(HMM)) expressed in the Baculovirus system. The relationship between actin filament velocity and the number of interacting M5(HMM) molecules indicates a duty cycle of greater than or equal to 50%. This high duty cycle would allow actin filament translocation and thus organelle transport by a few M5HMM molecules. Single molecule displacement data showed predominantly single step events of 20 nm and an occasional second step to 37 nm. The 20-nm unitary step represents the myosin V working stroke and is independent of the mode of M5(HMM) attachment to the motility surface or light chain content. The large M5HMM working stroke is consistent with the myosin V neck acting as a mechanical lever. The second step is characterized by an increased displacement variance, suggesting a model for how the two heads of myosin V function in processive motion.
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