Endocrinology, Vol 112, 1895-1902, Copyright © 1983 by Endocrine Society

ARTICLES

Ca2+-calmodulin-dependent phosphorylation of soluble and nuclear proteins in the rat ovary

ET Maizels and RA Jungmann

Studies were undertaken to determine if calmodulin-regulated Ca2+- dependent protein kinase system(s) exist in the prepubertal rat ovary. Phosphorylation studies were performed with ovarian cytosol, calmodulin- depleted cytosol, and nuclear extracts. In vitro phosphorylation of endogenous substrate proteins was accomplished by incubation of tissue fractions with [gamma-32P]ATP followed by electrophoretic separation and autoradiographic demonstration of phosphorylated proteins. Calmodulin-dependent phosphorylations of a cytosol protein, mol wt, 95,000, and of three nuclear proteins in the mol wt range of 50,000- 60,000, were established by demonstrating: Ca2+ requirement; inhibition by the phenothiazine derivative chlorpromazine; and dependence upon addition of exogenous calmodulin to the calmodulin-depleted cytosol, or to the nuclear extract. These findings demonstrate the presence of rat ovarian cytosol and nuclear Ca2+-calmodulin-dependent protein kinase activities capable of recognizing endogenous substrate proteins.

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