Regulation of the actin-activated ATPase activity of Acanthamoeba myosin I by cross-linking actin filaments

J. P. Albanesi, T. J. Lynch, H. Fujisaki, E. D. Korn

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6 Scopus citations


The actin-activated Mg2+-ATPase activity of phosphorylated Acanthamoeba myosin I was previously shown to be cooperatively dependent on the myosin concentration (Albanesi, J.P., Fujisaki, H., and Korn, E.D. (1985) J. Biol. Chem. 260, 11174-11179). This observation was rationalized by assuming that myosin I contains a high-affinity and a low-affinity F-actin-binding site and that binding at the low-affinity site is responsible for the actin-activated ATPase activity. Therefore, enzymatic activity would correlate with the cross-linking of actin filaments by myosin I, and the cooperative increase in specific activity at high myosin:actin ratios would result from the fact that cross-linking by one myosin molecule would increase the effective F-actin concentration for neighboring myosin molecules. This model predicts that high specific activity should occur at myosin:actin ratios below that required for cooperative interactions if the actin filaments are cross-linked by catalytically inert cross-linking proteins. This prediction has been confirmed by cross-linking actin filaments with either of three gelation factors isolated from Acanthamoeba, one of which has not been previously described, or by enzymatically inactive unphosphorylated Acanthamoeba myosin I.

Original languageEnglish (US)
Pages (from-to)10445-10449
Number of pages5
JournalJournal of Biological Chemistry
Issue number22
StatePublished - 1986

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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