A site of interaction between pleckstrin's PH domains and G(beta gamma)

Pleckstrin is a 40 kDa substrate for protein kinase C found in platelets and neutrophils. Based upon its sequence, pleckstrin contains two of the recently-described PH domains that are thought to be binding motifs for phosphatidyl 4,5-bisphosphate (PIP2) and/or G protein beta gamma heterodimers (G(beta gamma)). In the present studies we have examined the interaction between pleckstrin and G(beta gamma) by incubating pleckstrin fusion proteins with lysates from human platelets. In this analysis, both the N-terminal and C-terminal PH domains from pleckstrin bound G(beta gamma) in vitro, as did peptides containing as little as the first 30 residues of the C-terminal pleckstrin PH domain. Introduction of a point mutation into this region, analogous to the mutation in the Btk PH domain that causes X-linked immunodeficiency disease (XID) in mice, dramatically disrupted this interaction. We propose that pleckstrin may interact with G(beta gamma) and that one potential site for this interaction involves the first 30 residues of pleckstrin's C-terminal PH domain.