BRYOSTATIN BINDING SITE OF PKC AND BRYOSTATIN AN

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The marine natural product, bryostatin, is in Phase II clinical trials in Britain for the treatment of cancer. The very low natural abundance of this class of compounds, a few parts per billion to several hundred parts per billion, and a lengthy synthesis of one member may hinder wider clinical studies. Bryostatins wide variety of biological effects is traced to binding to PKC(protein kinase C). The size and complexity of PKC precludes detailed investigation of its phorbol ester/diacylglycerol binding domain by X-ray crystallography or NMR. Smaller peptides (approximately 50 residues) which incorporate this subdomain can be studied by NMR. The binding of bryostatin to these peptides will be quantified using [26-3H]-bryostatin and qualitatively by NMR using 13C, 15N labeled peptides. As a medium resolution structure of one of these peptides is in hand, the determination of the exact structure of its bryostatin binding domain is a reasonable goal. Once the binding site is known, then the conformation of bryostatin in this site can be determined by 2-D NMR. Knowledge of this fit to the binding site will enable simplified analogs to be made which incorporate the features necessary for binding. Routes to potentially useful analogs are provided.