Isolation and characterisation of Rck2p, a putative receptor of activated C kinase in Saccharomyces cerevisiae

Activated protein kinase C (PKC) was shown to translocate from the cytosol to the particulate fraction in mammalian cells. Recent evidence has indicated that PKC translocation is more complex than originally thought and is mediated by receptors of activated C. kinase (RACKs). RCK2 is a putative RACK gene in the yeast Saccharomyces cerevisiae which was isolated using an immunological screen. The screen detected yeast polypeptides which interacted with exogenously added mammalian PKC. RCK2, predicted to encode a polypeptide of ~33kDa, is a novel gene/protein. Analysis of an Deltarck2 mutant indicated that Rck2p is not an essential protein, and phenotype analysis failed to suggest an in vivo function for this protein. Overexpression of Rck2p, as a fusion protein in an E. coli host, revealed that it becomes tightly associated with the bacterial chaperone GroEL. The merits of Rck2p being a yeast homologue of a mammalian RACK and the physiological relevance of its interaction with GroEL are discussed.