MUTATION IN THE PLECKSTRIN HOMOLOGY DOMAIN OF THE HUMAN PHOSPHOLIPASEC-DELTA-1 GENE IS ASSOCIATED WITH LOSS OF FUNCTION

The delta-type phospholipase C (PLC) is thought to be evolutionally th e most basal form in the mammalian PLC family. One of the delta-type i soforms, PLC-delta 1, binds to both phosphatidylinositol 4,5-bisphosph ate (PtdIns(4,5)P-2) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P-3) with a high affinity via its pleckstrin homology (PH) domain. We repor t here a missense mutation in the region encoding the C-terminal PH do main of the human PLC-delta 1. This is also the first report of a muta tion in the human PLC genes. A single base substitution (G to A) cause s the amino acid replacement, Arg105 to His. Site directed mutagenesis of the glutathione-S-transferase (GST)/PLC-delta 1 fusion protein cha nging Arg105 to His resulted in a fourfold decrease in the affinity of specific Ins(1,4,5)P-3 binding and a reduction in PtdIns(4,5)P-2 hydr olysing activity to about 40% of that of the wild-type enzyme. This re markable loss of function can be interpreted in terms of a conformatio nal change in the PH domain. (C) 1998 Academic Press.