Switching of myosin-V motion between the lever-arm swing and brownian search-and-catch.
Motor proteins are force-generating nanomachines that are highly adaptable to their ever-changing biological environments and have a high energy conversion efficiency. Here we constructed an imaging system that uses optical tweezers and a DNA handle to visualize elementary mechanical processes of a nanomachine under load. We apply our system to myosin-V, a well-known motor protein that takes 72 nm 'hand-over-hand' steps composed of a 'lever-arm swing' and a 'brownian search-and-catch'. We find that the lever-arm swing generates a large proportion of the force at low load (<0.5 pN), resulting in 3 k(B)T of work. At high load (1.9 pN), however, the contribution of the brownian search-and-catch increases to dominate, reaching 13 k(B)T of work. We believe the ability to switch between these two force-generation modes facilitates myosin-V function at high efficiency while operating in a dynamic intracellular environment.
Soft Biosystem Group, Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
Keisuke
K
Fujita
Mitsuhiro
M
Iwaki
Atsuko H
AH
Iwane
Lorenzo
L
Marcucci
Toshio
T
Yanagida
D004076:Digoxigenin / Q000737:chemistry; D006801:Humans; D024701:Myosin Type V / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D052898:Optical Tweezers
D024701:Myosin Type V; D004076:Digoxigenin