Two calcium/calmodulin-dependent protein kinases, which are highly concentrated in brain, phosphorylate protein I at distinct sites
- Creators
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Kennedy, Mary B.
- Greengard, Paul
Abstract
Two calcium-stimulated protein kinase activities (ATP:protein phosphotransferase, EC 2.7.1.37) that phosphorylate protein I, a specific synaptic protein, have been identified in homogenates of rat brain. One of these is found in both the particulate and cytosolic fractions and phosphorylates a region of protein I that is phosphorylated in intact synaptosomes in response to calcium but not to cyclic AMP. The stimulation by calcium of the particulate enzyme and of the partially purified cytosolic enzyme requires the addition of calmodulin. It is not yet known whether the particulate and cytosolic enzymes are related. A second calcium-stimulated protein I kinase is found only in the cytosol and phosphorylates a region of protein I that is phosphorylated in intact synaptosomes in response to either calcium or cyclic AMP. The calcium stimulation of this latter kinase is probably mediated by calmodulin, judging from its inhibition by low concentrations of trifluoperazine. Both of the calcium-stimulated protein I kinases are more highly concentrated in brain than in other tissues. The two cytosolic kinases are distinguishable from each other and from myosin light chain kinase and phosphorylase b kinase by their substrate specificities and their chromatographic behavior on DEAE-cellulose.
Additional Information
© 1981 by the National Academy of Sciences. Contributed by Paul Greengard, December 1, 1980. We thank Teresa McGuinness, Rodrigo Andrade, and Penelope E. Miller for help with some of the experiments and Annette E. Gwardyak and Karen J. Hageman for help in preparing the manuscript. This work was supported by U.S. Public Health Service Grants MH-17387 and NS-08440 (to P.G.) and a grant from the McKnight Foundation (to P.G.). This work was done during the tenure of a Muscular Dystrophy Association Research Fellowship awarded to M.B.K. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.Files
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Additional details
- PMCID
- PMC319995
- Eprint ID
- 8848
- Resolver ID
- CaltechAUTHORS:KENpnas81
- Created
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2007-09-21Created from EPrint's datestamp field
- Updated
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2019-10-02Created from EPrint's last_modified field