Viscosity and solute dependence of F-actin translocation by rabbit skeletal heavy meromyosin

Departments of 1  Radiology, 2  Physiology and Biophysics, and 3  Zoology, University of Washington, Seattle, Washington 98195 We tested the hypothesis that solvent viscosity affects translocation of rhodamine phalloidin-labeled F-actin by rabbit skeletal heavy meromyosin (HMM). When viscosity was i...

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Published in:American Journal of Physiology: Cell Physiology 2000-06, Vol.278 (6), p.C1088-C1098
Main Authors: Chase, P. Bryant, Chen, Ying, Kulin, Kristi L, Daniel, Thomas L
Format: Article
Language:English
Subjects:
Actins - physiology
Adenosine Triphosphatases - metabolism
Animals
Dextrans - pharmacology
Fructose - pharmacology
Glycerol - pharmacology
Kinetics
Muscle, Skeletal - physiology
Myosin Subfragments - physiology
Phalloidine
Polyethylene Glycols - pharmacology
Rabbits
Solutions
Sucrose - pharmacology
Viscosity
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Summary:Departments of 1  Radiology, 2  Physiology and Biophysics, and 3  Zoology, University of Washington, Seattle, Washington 98195 We tested the hypothesis that solvent viscosity affects translocation of rhodamine phalloidin-labeled F-actin by rabbit skeletal heavy meromyosin (HMM). When viscosity was increased using either glycerol, fructose, sucrose, or dextran (1.5, 6.0, or 15-20 kDa mol mass), there was little or no effect on the fraction of moving filaments, whereas sliding speed decreased in inverse proportion to viscosity. The results could be explained neither by an effect of osmotic pressure at high solute concentrations nor by altered solvent drag on the actin filament. Elevated viscosity inhibited HMM ATPase activity in solution, but only at much higher viscosities than were needed to reduce sliding speed. Polyethylene glycols (300, 1,000, or 3,000 mol wt) also inhibited speed via elevated viscosity but secondarily inhibited by enhancing electrostatic interactions. These results demonstrate that a diffusion-controlled process intrinsic to cross-bridge cycling can be limiting to actomyosin function. in vitro motility assay; protein dynamics of biological motors; diffusion; sugars; polyethylene glycols
ISSN:0363-6143
1522-1563
DOI:10.1152/ajpcell.2000.278.6.c1088