CALCIUM-INDEPENDENT PHOSPHOLIPID DIOLEIN-DEPENDENT PHOSPHORYLATION OF A SOLUBLE OVARIAN MR 80000 SUBSTRATE PROTEIN - BIOCHEMICAL CHARACTERISTICS

Soluble ovarian extracts were incubated with protein kinase effectors in the presence of [γ32P]ATP and proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Autoradiograms revealed phosphorylation of an ovarian Mr = 80 000 substrate in the presence of EGTA ([ethylenebis(oxyethylenenitrilo)]tetraacetic acid), phosphatidylserine and 1,2-diolein. In contrast to a classical response pattern to C-kinase effectors, the ovarian Mr = 80 000 phosphorylation was inhibited by 2·10-7 M or greater free Ca2+. The ovarian Mr = 80 000 substrate was distinguished from the myristoylated acidic Mr = 80 000 C-kinase substrate of brain tissue on the basis of heat stability and phosphorylative response to effectors. Phosphorylation of the exogenous substrate myelin basic protein by DEAE-resolved ovarian kinase showed the variant effector dependence, maximal in the presence of EGTA, phospatidylserine and 1,2-diolein. Finally, the effect of Ca2+ on ovarian Mr = 80 000 [32P]phosphate content could not be accounted for by post-phosphorylation activities, or by DEAE-resolvable or hydroxylapatite-resolvable inhibitory activities. © 1990.