Mutants of Escherichia coli defective in membrane phospholipid synthesis. Properties of wild type and Km defective sn-glycerol-3-phosphate acyltransferase activities.
The sn-glycerol-3-phosphate (glycerol-P) acyltransferase, the first enzyme of membrane phospholipid synthesis in Escherichia coli, was investigated in a wild type and a mutant strain defective in this activity. The mutant strain, selected as a glycerol-P auxotroph, was previously shown to contain a glycerol-P acyltransferase activity with an apparent Km for glycerol-P 10 times higher than that of its parent or revertants. The membranous mutant glycerol-P acyltransferase but did not appear to be thermolabile in vivo. Revertants no longer requiring glycerol-P for growth, showed glycerol-P acyltransferase activity with thermolability properties similar to the wild type. The second phospholipid biosynthetic enzyme, 1-acylglycerol-P acyltransferase, was not thermolabile in membranes containing a thermolabile glycerol-P acyltransferase activity. The pH optimum for the mutant acyltransferase was over 1 pH unit higher than that of the parental activity. Further, the mutant and wild type glycerol-P acyltransferase differed in their response to magnesium chloride and potassium chloride. The palmitoyl-CoA dependence of the wild type and mutant glycerol-P acyltransferase activities were different. The mutant glycerol-P acyltransferase activity was inhibited greater than 90% by Triton X-100 under conditions where the wild type activity was not affected. These experiments provide novel information about the wild type glycerol-P acyltransferase activity of E. coli and provide six additional lines of evidence for the mutant character of the glycerol-P acyltransferase in the mutant strains.
D000217:Acyltransferases / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D004355:Drug Stability; D004926:Escherichia coli / Q000201:enzymology*; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009154:Mutation; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D013045:Species Specificity; D013696:Temperature
D011092:Polyethylene Glycols; D011189:Potassium Chloride; D000217:Acyltransferases; D005992:Glycerol-3-Phosphate O-Acyltransferase; D008274:Magnesium