No abstract

Solubilized glycerophosphate acyltransferase from Escherichia coli was reconstituted in small unilamellar vesicles consisting of phosphatidylcholine/phosphatidylglycerol in a molar ratio of 4: 1. Glycerol 3-phosphate, trapped inside these vesicles, cannot be acylated by the enzyme upon addition of extra-vesicular palmitoyl-CoA. Thus, substratebinding sites and active sites are asymmetrically oriented in the model membrane.When up to 10mo1/100mol lysophosphatidic acid was incorporated in the vesicles a decrease in glycerophosphate acyltransferase activity is observed at amounts exceeding l mol % lysophosphatidate. Similar experiments, using lysophosphatidylcholine and phosphatidic acid, suggest the decrease to result from an increase in negative surface charge. Reconstituted glycerophosphate acyltransferase exhibits a preference for palmitoyl-CoA over oleoyl-CoA. This preference increases considerably at elevated temperatures. The glycerophosphate acyltransferase could, therefore, participate in the temperature-dependent changes in the fatty acid composition of the phospholipids in E. coli.