Phosphatidic acid accumulation in the membranes of Escherichia coli mutants defective in CDP-diglyceride synthetase.
نویسندگان
چکیده
CTP-phosphatidic acid cytidylyltransferase (CDP-diglyceride synthetase) is a key enzyme in the biogenesis of membrane phospholipids in Escherichia coli. Using a modification of a previously described autoradiographic screening procedure (Raetz, C. R. H. (1975) Proc. Natl. Acad. Sci. U.S.A. 72, 2274-2278), we have isolated six mutant strains in which the specific activity of the synthetase is 1 to 10% that of the wild type, as judged by in vitro assays. The synthesis of dCDP-diglyceride, as well as CDP-diglyceride, is defective in these organisms. The mutations responsible for the enzyme defects (designated cds) all map in the same location near minute 4 on the chromosome. Although none of the mutants obtained are temperature-sensitive for growth, all of them exhibit significantly elevated levels of phosphatidic acid in vivo. The highest increase is observed in the mutant GL60, in which phosphatidic acid constitutes about 5% of the membrane lipid, in contrast to 0.2% in typical wild type strains. The accumulation of phosphatidic acid occurs primarily at the expense of phosphatidylglycerol and cardiolipin, but the total lipid-to-protein ratio of GL60 is nearly normal. In vivo labeling of GL60 with 32Pi suggests that the increased phosphatidic acid pool is the result of a partial metabolic block early in the phospholipid pathway, but that most of this expanded pool is nonetheless available for de novo synthesis.
منابع مشابه
Phosphatidic Acid Accumulation in the Membranes of Escherichia coli
CTP-phosphatidic acid cytidylyltransferase (CDP-diglyceride synthetase) is a key enzyme in the biogenesis of membrane phospholipids in Escherichia coli. Using a modification of a previously described autoradiographic screening procedure (Raetz, C. R. H. (1975) h c . Natl. A d Sei. U. S. A. 72, 2274-2278), we have isolated six mutant strains in which the specific activity of the synthetase...
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ورودعنوان ژورنال:
- The Journal of biological chemistry
دوره 255 4 شماره
صفحات -
تاریخ انتشار 1980