PHYSIOLOGICAL INHIBITORS OR PROTEIN-KINASE-C

Increasing numbers of proteins that have the capacity of interacting w ith protein kinase C isozymes in vitro and inhibiting their enzymatic activity in a noncompetitive manner have been purified. While these pr oteins can be hypothesized to be part of a tight regulatory system for protein kinase C enzymatic activity, critical examinations of the rol es of these proteins in the context of whole cells have not yet been p erformed. Interesting new data suggest that some of the classes of pro tein kinase C inhibitors may have a much broader role of interacting w ith multiple types of kinases and proto-oncogene products. cDNAs encod ing a number of these inhibitor proteins have been isolated, which wil l allow the design and implementation of experiments on their cell bio logy and help address their function outside of the context of their o perational definitions.