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Is Ca 2 + ‐Calmodulin‐Dependent Protein Phosphorylation in Rat Brain Modulated by Carboxylmethylation?
Author(s) -
Billingsley Melvin L.,
Velletri Paul A.,
Lovenberg Walter,
Kuhn Donald,
Goldenring James R.,
DeLorenzo Robert J.
Publication year - 1985
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1985.tb08781.x
Subject(s) - calmodulin , phosphorylation , chemistry , biophysics , biochemistry , biology , enzyme
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 Ca 2+ ‐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 CH 3 /μg protein or 0.15–1.12 mol CH 3 /mol of holoenzyme. Analysis of ATP binding in cytosol with the use of the photoaffinity probe [ 32 P]8‐azido‐ATP indicated that carboxylmethylation reduced ATP binding. These results suggest that carboxylmethylation of Ca 2+ ‐calmodulin protein kinase may modulate the activity of this enzyme in rat brain.