The mechanism of regulation of actomyosin subfragment 1 ATPase.

Steven Rosenfeld, E. W. Taylor

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

The mechanism of regulation of actin-subfragment 1 nucleoside triphosphatase is described in terms of the rate and equilibrium constants of a relatively simple kinetic scheme: (Formula: see text) where T, D, and Pi are nucleoside triphosphate, nucleoside diphosphate, and inorganic phosphate, respectively; Ka, Kb, and Kc are association constants; the ki are first-order rate constants; A is regulated actin (actin-tropomyosin-troponin); and M is subfragment 1. Calcium binding to regulated actin had little effect on step 2; k2 was almost unaffected, and k-2 increased, at most, 2-fold. k-1 and k3 increased 10-20-fold for ATP and 3-5-fold for 1-N6-ethenoadenosine triphosphate as substrates. Kb and Kc increased by less than 50%, whereas Ka increased 6-10-fold. The primary effect in regulation is on the rate of a conformational change which determines the rate of dissociation of ligands bound to the active site. The measurements probably underestimate the ratio of rate constants of product dissociation for active and relaxed states of actin because of heterogeneity. The kinetic evidence can be explained by a partial steric blocking mechanism or by a conformational (nonsteric) mechanism.

Original languageEnglish (US)
Pages (from-to)9984-9993
Number of pages10
JournalJournal of Biological Chemistry
Volume262
Issue number21
StatePublished - Jul 25 1987
Externally publishedYes

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Myosin Subfragments
Actins
Rate constants
Nucleosides
Ethenoadenosine Triphosphate
Nucleoside-Triphosphatase
Tropomyosin
Kinetics
Troponin
Diphosphates
Equilibrium constants
Catalytic Domain
Adenosine Triphosphate
Phosphates
Association reactions
Ligands
Calcium
Substrates

ASJC Scopus subject areas

  • Biochemistry

Cite this

The mechanism of regulation of actomyosin subfragment 1 ATPase. / Rosenfeld, Steven; Taylor, E. W.

In: Journal of Biological Chemistry, Vol. 262, No. 21, 25.07.1987, p. 9984-9993.

Research output: Contribution to journalArticle

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