Ohtsuka T, Nishijima M, Akamatsu Y
Department of Biochemistry and Cell Biology, National Institute of Health, Tokyo, Japan.
J Biol Chem. 1993 Oct 25;268(30):22908-13.
Phosphatidylglycerophosphate (PGP) synthase catalyzes a reaction involved in the synthesis of phosphatidylglycerol (PG), which serves as a metabolic precursor for cardiolipin (CL), found primarily in the mitochondrial membranes of eukaryotic cells. We isolated a Chinese hamster ovary cell mutant (designated PGS-S) with a specific lesion in PGP synthase by using an in situ enzymatic assay for the enzyme. This mutant was obtained by introducing a second mutation into mutant PGS-P that had been generated by first-step mutagenesis. The PGP synthase activities in cell extracts of mutant PGS-S grown at 33 and 40 degrees C were 14 and 1% of those in the wild type cells, respectively; in addition, PGP synthase in cell extracts of mutant PGS-S exhibited higher sensitivity to heat than that of the wild type. Mutant PGS-S also showed a temperature-dependent defect in the synthesis of PG and CL in vivo, together with temperature sensitivity for cell growth. A temperature-resistant revertant of mutant PGS-S simultaneously restored PGP synthase activity and the ability to synthesize PG and CL in vivo to nearly the same levels as those of mutant PGS-P. These results constitute genetic evidence that PGP synthase is responsible for PG synthesis and is essential for cell growth.
磷脂酰甘油磷酸（PGP）合酶催化参与磷脂酰甘油（PG）合成的反应，PG是心磷脂（CL）的代谢前体，主要存在于真核细胞的线粒体膜中。我们通过使用该酶的原位酶促测定法，分离出了一株PGP合酶存在特定损伤的中国仓鼠卵巢细胞突变体（命名为PGS-S）。该突变体是通过将第二步突变引入经第一步诱变产生的突变体PGS-P中获得的。在33℃和40℃下生长的突变体PGS-S细胞提取物中的PGP合酶活性分别为野生型细胞的14%和1%；此外，突变体PGS-S细胞提取物中的PGP合酶比野生型对热更敏感。突变体PGS-S在体内PG和CL的合成中也表现出温度依赖性缺陷，同时对细胞生长具有温度敏感性。突变体PGS-S的一个耐温回复突变体同时将PGP合酶活性以及体内合成PG和CL的能力恢复到与突变体PGS-P几乎相同的水平。这些结果构成了遗传学证据，表明PGP合酶负责PG的合成，并且对细胞生长至关重要。
