The calcium binding properties of phosphorylated and unphosphorylated cardiac and skeletal myosins

M. J. Holroyde, J. D. Potter, R. J. Solaro

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Abstract

Porcine left ventricular cardiac myosin and rabbit white skeletal myosin were phosphorylated by rabbit skeletal myosin light chain kinase and their Ca2+ binding properties were examined by equilibrium dialysis techniques. No significant effect of phosphorylation on the Ca2+ binding properties of these myosins was observed. Both types of striated muscle myosins bound approximately 2 mol of Ca2+/mol of myosin with similar affinities of 3 x 107 M-1. In the presence of 3 x 10-4 M Mg2+ the myosins bound Ca2+ with a reduced affinity of 3 to 4 x 105 M-1. Assuming competition between Mg2+ and Ca2+ for the binding sites on myosin, the changes in Ca2+ binding can be accounted for by a Mg2+ affinity of 2.5 to 3.0 x 105 M-1.

Original languageEnglish (US)
Pages (from-to)6478-6482
Number of pages5
JournalJournal of Biological Chemistry
Volume254
Issue number14
StatePublished - Dec 1 1979

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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