Phosphorylation by casein kinase II alters the biological activity of calmodulin

D. B. Sacks, H. W. Davis, J. P. Williams, E. L. Sheehan, J. G.N. Garcia, J. M. McDonald

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44 Scopus citations

Abstract

Calmodulin is the major intracellular Ca2+-binding protein, providing Ca2+-dependent regulation of numerous intracellular enzymes. The phosphorylation of calmodulin may provide an additional mechanism for modulating its function as a signal transducer. Phosphocalmodulin has been identified in tissues and cells, and calmodulin is phosphorylated both in vitro and in intact cells by various enzymes. Phosphorylation of calmodulin on serine/threonine residues by casein kinase II decreases its ability to activate both myosin-light-chain kinase and cyclic nucleotide phosphodiesterase. For myosin-light-chain kinase the primary effect is an inhibition of the V(max.) of the reaction, with no apparent change in the concentration at which half-maximal velocity is attained (K0.5) for either Ca2+ or calmodulin. In contrast, for phosphodiesterase, phosphorylation of calmodulin significantly increases the K0.5 for calmodulin without noticeably altering the V(max.) or the K0.5 for Ca2+. The higher the stoichiometry of phosphorylation of calmodulin, the greater the inhibition of calmodulin-stimulated activity for both enzymes. Therefore the phosphorylation of calmodulin by casein kinase II appears to provide a Ca2+-independent mechanism whereby calmodulin regulates at least two important target enzymes, myosin-light-chain kinase and cyclic nucleotide phosphodiesterase.

Original languageEnglish (US)
Pages (from-to)21-24
Number of pages4
JournalBiochemical Journal
Volume283
Issue number1
DOIs
StatePublished - Jan 1 1992
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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    Sacks, D. B., Davis, H. W., Williams, J. P., Sheehan, E. L., Garcia, J. G. N., & McDonald, J. M. (1992). Phosphorylation by casein kinase II alters the biological activity of calmodulin. Biochemical Journal, 283(1), 21-24. https://doi.org/10.1042/bj2830021