A somatic cell mutant defective in phosphatidylglycerophosphate synthase, with impaired phosphatidylglycerol and cardiolipin biosynthesis.
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.
Ohtsuka
T
T
Department of Biochemistry and Cell Biology, National Institute of Health, Tokyo, Japan.
Nishijima
M
M
Akamatsu
Y
Y
D000818:Animals; D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; D016466:CHO Cells; D002308:Cardiolipins / Q000096:biosynthesis*; D002455:Cell Division; D006224:Cricetinae; D004795:Enzyme Stability; D005020:Ethyl Methanesulfonate / Q000633:toxicity; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000378:metabolism; D016296:Mutagenesis; D010715:Phosphatidylglycerols / Q000096:biosynthesis*; D010743:Phospholipids / Q000378:metabolism; D013696:Temperature; D013816:Thermodynamics; D017855:Transferases (Other Substituted Phosphate Groups) / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
D002308:Cardiolipins; D010715:Phosphatidylglycerols; D010743:Phospholipids; D005020:Ethyl Methanesulfonate; D005992:Glycerol-3-Phosphate O-Acyltransferase; D017855:Transferases (Other Substituted Phosphate Groups); D051607:CDP-Diacylglycerol-Inositol 3-Phosphatidyltransferase; C020676:CDP-diacylglycerol-glycerol-3-phosphate 3-phosphatidyltransferase