PROTEIN-KINASE-C - A QUESTION OF SPECIFICITY

Following the initial identification of protein kinase C (PKC) by Nish izuka and co-workers in the late seventies, a wealth of information on this protein kinase has accumulated. Perhaps most striking was the re alization that PKC is not just a single polypeptide but in fact consis ts of a large family of related proteins. These PKC isotypes are uniqu e, not only with respect to primary structure, but also on the basis o f expression patterns, subcellular localization, activation in vitro a nd responsiveness to extracellular signals. This review focuses on the heterogeneity within the PKC family and highlights some of the recent evidence that the isotypes might have separate and unique functions i n the cell.