A site of interaction between pleckstrin's PH domains and G βγ

Abstract

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 (PIP 2) and/or G protein βγ heterodimers (G βγ). In the present studies we have examined the interaction between pleckstrin and G βγ 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 βγ 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 βγ, and that one potential site for this interaction involves the first 30 residues of pleckstrin's C-terminal PH domain.