期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：24
页码：13726-13731
DOI：10.1073/pnas.96.24.13726
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Myosin V is an unconventional myosin proposed to be processive on actin filaments, analogous to kinesin on a microtubule [Mehta, A. D., et al. (1999) Nature (London) 400, 590-593]. To ascertain the unique properties of myosin V that permit processivity, we undertook a detailed kinetic analysis of the myosin V motor. We expressed a truncated, single-headed myosin V construct that bound a single light chain to study its innate kinetics, free from constraints imposed by other regions of the molecule. The data demonstrate that unlike any previously characterized myosin a single-headed myosin V spends most of its kinetic cycle (>70%) strongly bound to actin in the presence of ATP. This kinetic tuning is accomplished by increasing several of the rates preceding strong binding to actin and concomitantly prolonging the duration of the strongly bound state by slowing the rate of ADP release. The net result is a myosin unlike any previously characterized, in that ADP release is the rate-limiting step for the actin-activated ATPase cycle. Thus, because of a number of kinetic adaptations, myosin V is tuned for processive movement on actin and will be capable of transporting cargo at lower motor densities than any other characterized myosin.
