Calmodulin and Ca2+- and calmodulin-dependent protein kinase in rat anterior pituitary gland.
Calmodulin and Ca2+- and calmodulin-dependent protein kinase were identified in the rat anterior pituitary gland. The concentration of calmodulin was 1.18 +/- 0.11 microgram/mg protein (n = 7) in the cytosol fraction. The calmodulin of the anterior pituitary gland co-migrated with brain calmodulin on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Ka value of the partially purified enzyme for Ca2+ was 3.3 microM in the presence of 0.30 microM calmodulin. Trifluoperazine and chlorpromazine, calmodulin-interacting agents, inhibited enzyme activity, with Ki values of 1.3 and 2.6 X 10(-5) M, respectively. The enzyme was resolved into two peaks of activity, with sedimentation coefficients of 5.5 S and 16.5 S, by sucrose density gradient centrifugation. At least nine proteins were phosphorylated by the enzyme in a Ca2+- and calmodulin-dependent manner. In light of these results, the possibility that calmodulin and the calmodulin-activatable protein kinase system are involved in the mediation of the Ca2+ effect on hormone release from the anterior pituitary gland must be given consideration.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D010903:Pituitary Gland, Anterior / Q000201:enzymology*; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D011494:Protein Kinases; D002118:Calcium