Beta-Spectrin, Pleckstrin Homology Domain
The pleckstrin homology (PH) domain of Drosophila melanogaster beta-spectrin has been found in many proteins involved in signal transduction and cytoskeletal function. In this protein group,the PH domain is as common as the SH2 (src homology 2) and SH3 domains. This domain has been shown to bind the beta-gamma subunits of G-proteins as well as phosphatidylinositol 4,5-bisphosphate (PIP2). It is thought that the PH domain of beta-spectrin has a part in the association of spectrin with the plasma membrane of cells.
The pleckstrin homology domain of beta-spectrin is 122 amino acid residues long. It consists of two antiparallel beta-sheets which are packed against one another forming a beta-sandwich which is shown in purple. Two right-hand alpha helices are shown in magenta, and a single 310 alpha helix is shown in gold.