Cyclic AMP-binding proteins : enhanced retention on membrane filters ty histone and protamine sulfate.

Polycations such as histone and protamine sulfate increase the efficiency of retention of cAMP-binding protein complexes on cellulose ester membrane filters. A 40,000 dalton cAMP-binding protein from calf ovaries was not retained on the membrane filters when assayed above pH 5.5. The addition of histone or protamine sulfate to the cAMP-binding assay completely abolished the pH dependency and resulted in retention of the complex. The retention of larger cAMP-binding proteins as well as the ovarian cAMP-dependent protein kinases showed little effect of histone at low pH values while a significant enhancement was observed above pH 7.0.