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C. -A new DAG-type template, based on the crystal structure of the PKCδ C1B domain in the complex with phorbol 13-acetate, is designed to clarify the molecular mechanisms of PKC activation. Optically active isobenzofuranones having a hydrophobic side chain are synthesized. Separation of the enantiomers of the monosilylated alcohol is achieved by means of a chiral phase column, cf. (VI)→(VII). Acyl chain analogues (X) are obtained by conversion of the pure (S)-enantiomer (VII) into (R)-enantiomers (X), which are generally more potent than the (S)-enantiomers. Pivaloyl derivative (Xa) is a strong PKC α ligand, and the structure-activity relationship is well explained by the binding model. -(BABA, Y.; OGOSHI, Y.; HIRAI, G.; YANAGISAWA, T.; NAGAMATSU, K.; MAYUMI, S.; HASHIMOTO, Y.; SODEOKA*, M.; Bioorg. Med.

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A specific binding protein for 12-O-tetradecanoylphorbol 13-acetate (TPA), different from protein kinase C (PKC) and histone H1, was purified from HeLa cell extract by the use of affinity gel pendanted with phorbol ester (TPA-GEL). The purified binding protein was identified as protein disulfide isomerase (PDI, EC 5.4.3.1) by peptide sequence analysis. The dissociation constants (Kd's) of TPA to PDI, histone H1 and PKCalpha were determined to be 1.03 x 10(-6) M, 5.70 x 10(-7) M, and 4.00 x 10(-7) m, respectively, by the surface plasmon resonance (SPR) method. TPA moderately inhibited PDI activity assessed in terms of reactivation of denatured RNase A.