Shimohama S, Kamiya S, Fujii M, Ogawa T, Kanamori M, Kawamata J, Imura T, Taniguchi T, Yagisawa H
Department of Neurology, Faculty of Medicine, Kyoto University, Japan.
Biochem Biophys Res Commun. 1998 Apr 28;245(3):722-8. doi: 10.1006/bbrc.1998.8307.
The delta-type phospholipase C (PLC) is thought to be evolutionally the most basal form in the mammalian PLC family. One of the delta-type isoforms, PLC-delta 1, binds to both phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) with a high affinity via its pleckstrin homology (PH) domain. We report here a missense mutation in the region encoding the C-terminal PH domain of the human PLC-delta 1. This is also the first report of a mutation in the human PLC genes. A single base substitution (G to A) causes the amino acid replacement, Arg105 to His. Site-directed mutagenesis of the glutathione-S-transferase (GST)/PLC-delta 1 fusion protein changing Arg105 to His resulted in a fourfold decrease in the affinity of specific Ins(1,4,5)P3 binding and a reduction in PtdIns(4,5)P2 hydrolysing activity to about 40% of that of the wild-type enzyme. This remarkable loss of function can be interpreted in terms of a conformational change in the PH domain.
δ型磷脂酶C（PLC）被认为是哺乳动物PLC家族中进化上最基本的形式。δ型同工型之一，PLC-δ1，通过其普列克底物蛋白同源（PH）结构域与磷脂酰肌醇4,5-二磷酸（PtdIns(4,5)P2）和肌醇1,4,5-三磷酸（Ins(1,4,5)P3）以高亲和力结合。我们在此报告人类PLC-δ1编码C末端PH结构域区域的一个错义突变。这也是人类PLC基因中突变的首次报道。单个碱基替换（G到A）导致氨基酸替换，即精氨酸105变为组氨酸。将谷胱甘肽-S-转移酶（GST）/PLC-δ1融合蛋白中的精氨酸105变为组氨酸的定点诱变导致特异性Ins(1,4,5)P3结合亲和力降低四倍，PtdIns(4,5)P2水解活性降低至野生型酶的约40%。这种显著的功能丧失可以用PH结构域的构象变化来解释。
