Nuclear protein kinase of brain: effect of S-100 protein.

The non-histone chromosomal protein fraction isolated from purified brain nuclei possesses protein kinase activity. 93% of this activity is lost by heating at 80 degrees C for 5 min. cAMP does not affect the reaction, but cGMP is inhibitory. In the presence of S-100, an acidic brain-specific protein, phosphate incorporation is enhanced 3 to 4 fold. Bovine serum albumin has no effect whereas histone inhibits activity.