CYCLIC-AMP-DEPENDENT PROTEIN-KINASE IN OVARIAN FOLLICLE CELLS OF STARFISH ASTERINA-PECTINIFERA

Adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase ( PKA) in ovarian follicle cells of the starfish Asterina pectinifera wa s studied. Protein kinase activity in follicle cell homogenate was act ivated by cAMP in a dose-dependent manner, and Ka was obtained with 10 (-7) M cAMP. The PKA. activity required Mg2+ at concentrations between 2 and 10 mM. On Sephacryl S-300 column chromatography of partially pu rified PKA, Mr of the holoenzyme was estimated to be about 180,000. [2 ,3-H-3]cAMP binding activity also suggested a regulatory subunit of Mr about 50,000. DE-52 column chromatography of the cell extract resolve d the enzyme activity into two peaks, which eluted between 0.05 and 0. 1 M NaCl (type I), and between 0.15 and 0.25 M NaCl (type II). The typ e I enzyme was the predominant form of PKA in starfish follicle cells. In a cell-free system, a 70 kDa protein was phosphorylated during inc ubation with [gamma-P-32]ATP in the presence of cAMP. These results su ggest that PKA stimulates the phosphorylation of a 70 kDa protein foll owing an increase in the level of cAMP. Copyright (C) 1996 Elsevier Sc ience Inc.