The dissociation of 1-N6-ethenoadenosine diphosphate from regulated actomyosin subfragment 1.

S. S. Rosenfeld, E. W. Taylor

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

The effective rate of dissociation of 1-N6-ethenoadenosine diphosphate (epsilon ADP) from the regulated actin X subfragment 1 X epsilon ADP complex of rabbit skeletal muscle is approximately 10-15 times smaller in the absence of calcium ion compared to the presence of calcium ion. The decrease in fluorescence emission with dissociation of the bound epsilon ADP fitted two exponential terms. The evidence is consistent with a kinetic scheme in which two first-order transitions precede the dissociation step: (Formula: see text) where D is epsilon ADP, A is regulated actin, M is subfragment 1, the asterisks refer to the degree of fluorescence enhancement, and AM(D) is a collision complex in equilibrium with free epsilon ADP. Both rate constants k-2 and k-1 were reduced approximately 15-fold in the absence of calcium ion. The rate constants for the dissociation of epsilon ATP, epsilon ADP X Pi, formed in the enzyme cycle, and epsilon ADP are all reduced in the absence of calcium ion; consequently, the primary effect in calcium regulation of the actin-subfragment 1 ATPase is on the rate constant of a transition (or transitions) between actomyosin-nucleoside phosphate complexes.

Original languageEnglish (US)
Pages (from-to)9994-9999
Number of pages6
JournalJournal of Biological Chemistry
Volume262
Issue number21
StatePublished - Jul 25 1987

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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