Evidence for cross-bridge order in contraction of glycerinated skeletal muscle

T. P. Burghardt, T. Ando, J. Borejdo

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The linear dichroism of iodoacetylrhodamine labels attached to the single reactive thiol groups of myosin beads was measured to determine the spatial orientation of myosin cross-bridges in single glycerinated skeletal muscle fibers. We have shown previously that in rigor the chromophoric labels are well ordered and assume an orientation nearly perpendicular to the fiber axis; in the presence of MgADP, a large fraction of probe remains well ordered but the probe attitude assumes a more slanted orientation; in relaxed muscle, the probe order is largely lost, implying a high degree of cross-bridge disorder. In this paper, we report that during isometric contraction a large fraction of the probe shows a high degree of order, suggesting the attachment of ≃65% of the cross-bridges to actin. These ordered cross-bridges have a probe attitude similar to that of the MgADP-induced static state and hence are in a mechanical state quite distinct from rigor.

Original languageEnglish (US)
Pages (from-to)7515-7519
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number24 I
StatePublished - 1983

ASJC Scopus subject areas

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