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pubmed:abstractText |
Binding of phorbol esters to protein kinase C (PKC) has been regarded as dependent on phospholipids, with phosphatidylserine being the most effective for reconstituting binding. By using a purified single cysteine-rich region from PKC delta expressed in Escherichia coli we were able to demonstrate that specific binding of [3H]phorbol 12,13-dibutyrate to the receptor still takes place in the absence of the phospholipid cofactor. However, [3H]phorbol 12,13-dibutyrate bound to the cysteine-rich region with 80-fold lower affinity in the absence than in the presence of 100 micrograms/ml phosphatidylserine. Similar results were observed with the intact recombinant PKC delta isolated from insect cells. When different phorbol derivatives were examined, distinct structure-activity relations for the cysteine-rich region were found in the presence and absence of phospholipid. Our results have potential implications for PKC translocation, for inhibitor design, and for PKC structural determination.
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pubmed:affiliation |
Molecular Mechanisms of Tumor Promotion Section, NCI, National Institutes of Health, Bethesda, Maryland 20892-4255, USA.
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