Endotoxin biosynthesis in Pseudomonas aeruginosa: enzymatic incorporation of laurate before 3-deoxy-D-manno-octulosonate.
Unlike Escherichia coli, living cells of Pseudomonas aeruginosa can complete the fatty acylation of lipid A when the biosynthesis of 3-deoxy-D-manno-octulosonate (Kdo) is inhibited (R. C. Goldman, C. C. Doran, S. K. Kadam, and J. O. Capobianco, J. Biol. Chem. 263:5217-5233, 1988). In this study, we demonstrate the presence of a novel enzyme in extracts of P. aeruginosa that can transfer lauroyl-acyl carrier protein (ACP) to a tetraacyl disaccharide-1,4'-bis-phosphate precursor of lipid A (termed lipid IVA) that accumulates in Kdo-deficient mutants of E. coli. Comparable E. coli extracts cannot transfer laurate from lauroyl-ACP to lipid IVA, only to (Kdo)2-lipid IVA (K. A. Brozek, and C. R. H. Raetz, J. Biol. Chem. 265:15410-15417, 1990). P. aeruginosa extracts do not utilize myristoyl- or R-3-hydroxymyristoyl-ACP instead of lauroyl-ACP to acylate lipid IVA. Laurate incorporation in P. aeruginosa extracts is dependent upon time, protein concentration, and the presence of Triton X-100 but is inhibited by lauroyl-coenzyme A. P. aeruginosa extracts transfer only one laurate to lipid IVA, whereas E. coli extracts can transfer two laurates to (Kdo)2-lipid IVA. These results demonstrate that incorporation of laurate into lipid A does not require prior attachment of Kdo in all gram-negative bacteria.
Mohan
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Department of Biochemistry, Merck Research Laboratories, Rahway, New Jersey 07065.
Raetz
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D036002:ADP Ribose Transferases; D000213:Acyl Carrier Protein / Q000378:metabolism; D000215:Acylation; D001427:Bacterial Toxins; D002474:Cell-Free System; D003593:Cytoplasm / Q000378:metabolism; D005098:Exotoxins / Q000096:biosynthesis*; D006017:Glycolipids / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis / Q000378:metabolism; D007850:Lauric Acids / Q000378:metabolism*; D008050:Lipid A / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013379:Substrate Specificity; D013400:Sugar Acids / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D000213:Acyl Carrier Protein; D001427:Bacterial Toxins; D005098:Exotoxins; D006017:Glycolipids; D006023:Glycoproteins; D007850:Lauric Acids; D008050:Lipid A; D013400:Sugar Acids; D014166:Transferases; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C090406:lauroyl-lipid IVA; C040142:lipid A precursors, bacterial; C002532:2-keto-3-deoxyoctonate; C030358:lauric acid; C088602:3-deoxy-2-octulosonic acid(2)-lipid IV(A); C019917:3-deoxy-D-manno-octulosonate transferase