Function of Cytidine Diphosphate-Diglyceride and Deoxycytidine Diphosphate-Diglyceride in the Biogenesis of Membrane Lipids in Escherichia coli
Year: 1973
Type: article
Abstract: CDP-diglyceride synthesized by chemical procedures is an efficient donor of phosphatidyl residues for the enzymatic synthesis of phospholipids in cell-free extracts of Escherichia coli.However, prior to the present work, CDP-diglyceride had never been isolated from living cells of E. coli or any other organism.We have, therefore, isolated and characterized the cytosine-containing liponucleotide fraction of E. coli and find it to be a mixture of almost equal amounts of CDPdiglyceride and dCDP-diglyceride.In these experiments, cells growing in the log phase were simultaneously labeled with tritiated cytosine and sn-glycero-3-[32P]phosphate.Under the conditions employed sn-glycero-3-[32P]phosphate was taken up without prior hydrolysis and was rapidly converted to labeled lipids.Since the intracellular pools of phosphatidic acid and of cytosine liponucleotides are very small and turn over very rapidly, the amounts of 32P in these fractions may be assumed to reflect their relative intracellular concentrations.The 32P radioactivity of the phosphatidic acid fraction was about 20 times higher than that of the cytosine liponucleotide fraction.Since phosphatidic acid is itself less than 1% of the lipids of E. coli, the steady state levels of the cytosine liponucleotides must be exceedingly low, supporting the hypothesis that the conversion of phosphatidic acid to cytosine liponucleotides may be ratemaking for the biosynthesis of the membrane phospholipids in this organism.The relative activity of CDP-diglyceride and of dCDPdiglyceride for the enzymatic synthesis of phosphatidylserine and of phosphatidylglycerophosphate was found to vary considerably with the concentration of liponucleotide used in the assay system.At concentrations greater than 0.1 mrvr, dCDP-diglyceride is relatively much more active in the synthesis of phosphatidylglycerophosphate than in the synthesis of phosphatidylserine.Below this concentration,
Source: Journal of Biological Chemistry
Authors: Christian R.H. Raetz, Eugene P. Kennedy
Institution: Harvard University
Language: English
Subfield: Biochemistry
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1568352573