Structure of the high affinity complex of inositol trisphosphate with a phospholipase C pleckstrin homology domain

AbstractThe X-ray crystal structure of the high affinity complex between the pleckstrin homology (PH) domain from rat phospholipase C-δ1 (PLC-δ1) and inositol-(1,4,5)-trisphosphate (Ins(1,4,5)P3) has been refined to 1.9 Å resolution. The domain fold is similar to others of known structure. Ins(1,4,5)P3 binds on the positively charged face of the electrostatically polarized domain, interacting predominantly with the β1/β2 and β3/β4 loops. The 4- and 5-phosphate groups of Ins(1,4,5)P3 interact much more extensively than the 1-phosphate. Two amino acids in the PLC-δ1 PH domain that contact Ins(1,4,5)P3 have counterparts in the Bruton's tyrosine kinase (Btk) PH domain, where mutational changes cause inherited agammaglobulinemia, suggesting a mechanism for loss of function in Btk mutants. Using electrostatics and varying levels of head-group specificity, PH domains may localize and orient signaling proteins, providing a general membrane targeting and regulatory function