Fraction of myosin cross-bridges bound to actin in active muscle fibers: Estimation by fluorescence anisotropy measurements

T. P. Burghardt, K. Ajtai

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Time-resolved and steady-state fluorescence anisotropy measurements from fluorescence-labeled myosin cross-bridges in single glycerinated skeletal muscle fibers in rigor, relaxed, MgADP-induced, and contracting states have been made in order to estimate the fraction of actin-bound cross-bridges in active muscle. When the plane of polarization of the excitation light is perpendicular to the fiber axis and its propagation vector has a component parallel to this axis, actin-bound cross-bridge states, such as rigor and MgADP-induced, have time-zero and steady-state anisotropies that are substantially lower than has the relaxed state. This difference provides a means of determining the fraction of cross-bridges bound to actin in active isometric fibers, by comparing the fluorescence anisotropy from active fibers with the anisotropy from bound and unbound cross-bridges in static states. By assuming that the active cross-bridges are either bound (in the manner of vigor or MgADP-induced states) or relaxed, we estimate that > 80% of the cross-bridges are actin-bound in active isometric fibers.

Original languageEnglish (US)
Pages (from-to)8478-8482
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume82
Issue number24
DOIs
StatePublished - 1985

ASJC Scopus subject areas

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