Is Ca2+ ‐Calmodulin‐Dependent Protein Phosphorylation in Rat Brain Modulated by Carboxylmethylation?

Melvin L. Billingsley, Paul A. Velletri, Walter Lovenberg, Donald Kuhn, James R. Goldenring, Robert J. DeLorenzo

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12 Scopus citations


Abstract: Calmodulin stimulation of protein kinase activity in calmodulin‐depleted preparations of rat brain cytosol or synaptosomal membranes was attenuated by prior carboxylmethylation of the enzyme source with purified protein‐O‐carboxylmethyltransferase. Similarly, calmodulin stimulation of highly purified Ca2+‐calmodulin‐dependent protein kinase was reduced if the kinase was exposed to methylating conditions prior to addition of calmodulin. Biochemical and acidic sodium dodecyl sulfate‐gel electrophoretic analyses indicated that all sources of protein kinase activity were substrates for methylation. The specific activity of methyl group incorporation into protein kinase increased with increasing purity of the preparation, reaching values of 1.72 pmol CH3/μg protein or 0.15–1.12 mol CH3/mol of holoenzyme. Analysis of ATP binding in cytosol with the use of the photoaffinity probe [32P]8‐azido‐ATP indicated that carboxylmethylation reduced ATP binding. These results suggest that carboxylmethylation of Ca2+‐calmodulin protein kinase may modulate the activity of this enzyme in rat brain.

Original languageEnglish (US)
Pages (from-to)1442-1450
Number of pages9
JournalJournal of neurochemistry
Issue number5
StatePublished - May 1985

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Cellular and Molecular Neuroscience


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