Phorbol diester receptor copurifies with protein kinase C.

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Abstract
The phorbol diester [tumor promoter] receptor present in the particulate fraction of rat brain was solubilized by divalent ion chelation in the absence of detergents. The soluble receptor was partially purified by (NH4)2SO4 precipitation, DEAE-cellulose and gel filtration chromatography. The purified receptor required exogenous phospholipid for activity and displayed a Kd of 7 nM for [3H]phorbol 12,13-dibutyrate. Biologically active phorbol analogs inhibited binding, whereas inactive analogs did not. The Ca2+-dependent, phospholipid-sensitive protein kinase C copurified with the phorbol receptor. Purified protein kinase C was activated directly by phorbol 12-myristate 13-acetate in the presence of phospholipid.