Switch 1 mutation S217A converts myosin V into a low duty ratio motor

Eva Forgacs, Takeshi Sakamoto, Suzanne Cartwright, Betty Belknap, Mihály Kovács, Judit Tóth, Martin R. Webb, James R. Sellers, Howard D. White

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22 Citations (Scopus)


We have determined the kinetic mechanism and motile properties of the switch 1 mutant S217A of myosin Va. Phosphate dissociation from myosin V-ADP-Pi (inorganic phosphate) and actomyosin V-ADP-Pi and the rate of the hydrolysis step (myosin V-ATP → myosin V-ADP-P i) were all ∼10-fold slower in the S217A mutant than in wild type (WT) myosin V, resulting in a slower steady-state rate of basal and filamentous actin (actin)-activated ATP hydrolysis. Substrate binding and ADP dissociation kinetics were all similar to or slightly faster in S217A than in WT myosin V and mechanochemical gating of the rates of dissociation of ADP between trail and lead heads is maintained. The reduction in the rate constants of the hydrolysis and phosphate dissociation steps reduces the duty ratio from ∼0.85 in WT myosin V to ∼0.25 in S217A and produces a motor in which the average run length on actin at physiological concentrations of ATP is reduced 10-fold. Thus we demonstrate that, by mutational perturbation of the switch 1 structure, myosin V can be converted into a low duty ratio motor that is processive only at low substrate concentrations.

Original languageEnglish
Pages (from-to)2138-2149
Number of pages12
JournalJournal of Biological Chemistry
Issue number4
Publication statusPublished - Jan 23 2009

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Forgacs, E., Sakamoto, T., Cartwright, S., Belknap, B., Kovács, M., Tóth, J., Webb, M. R., Sellers, J. R., & White, H. D. (2009). Switch 1 mutation S217A converts myosin V into a low duty ratio motor. Journal of Biological Chemistry, 284(4), 2138-2149. https://doi.org/10.1074/jbc.M805530200