Relation of turnover of membrane phospholipids to synthesis of membrane-derived oligosaccharides of Escherichia coli.

Previous reports from this laboratory (van Golde, L. M. G., Schulman, H., and Kennedy, E. P. (1973) Proc. N&l. Acad. Sci. U. S. A. 70, 1368-1372; Kennedy, E. P., Rumley, M. K., Schulman, H., and van Golde, L. M. G. (1976)J. Biol. Chem. 251, 4208-4213) described the discovery in Escherichia coli of a novel class of glucose-containing oligosaccharides (“the membrane-derived oligosaccharides”) variously substituted with sn-glycero-l-phosphate, phosphoethanolamine, and succinate. Strong, though indirect, evidence has been presented that the glycerophosphate and phosphoethanolamine residues are derived from the polar head groups of membrane phospholipids. We have now studied the turnover of membrane phospholipids in a strain (DF214) lacking phosphoglucose isomerase, that contains only traces of glucose (Vinopal, R. T., Hillman, J. D., Schulman, H., Rezhikoff, W. S., and Fraenkel, D. G. (1975) J. Bacterial. 122, 1172-1174). These cells, however, synthesize the membrane-derived oligosaccharides when glucose is provided in the growth medium. An analysis was, therefore, undertaken of phospholipid metabolism in this mutant strain with and without concurrent synthesis of the membrane-derived oligosaccharides. The turnover of both phosphatidylglycerol and cardiolipin is strikingly stimulated when these cells are grown in the presence of glucose. Evidence is also presented suggesting that the low rate of glucose-independent turnover may result from the transfer of the diglyceride moiety of phosphatidylglycerol or cardiolipin (or both) to the murein lipoprotein of the E. coli cell envelope.