| dc.description.abstract | Campylobacter jejuni is a Gram-negative pathogenic bacterium that is the leading cause of gastroenteritis worldwide. Like many other Gram-negative bacteria, C. jejuni produces a capsular polysaccharide (CPS) that helps improve the overall fitness of the organism and contributes to its pathogenicity. Previously, the structure of the CPS from the NCTC 11168 strain was determined, and has revealed the presence of a unique O-methyl phosphoramidate (MeOPN), that can be found on C-4 of a heptose and C-3 of an N-acetyl galactofuranose residue. Investigations into the role of MeOPN on the CPS suggest that it is involved in the evasion of immune responses, and serum resistance. Previously, the biosynthesis of the MeOPN modifications found on the CPS were unknown.
We have characterized the first four enzymes involved in the biosynthesis of the phosphoramidate moiety of the MeOPN modification. The first enzyme, Cj1418, is a novel glutamine kinase that catalyzes the ATP dependent phosphorylation of the amide nitrogen of L-glutamine, resulting in L-glutamine phosphate. Next, the nucleotidyl transferase, Cj1416 uses L-glutamine phosphate to displace pyrophosphate from CTP, forming CDP-L-glutamine. CDP-L-glutamine is then hydrolyzed by Cj1417, releasing glutamate and cytidine diphosphoramidate. Cj1415 catalyzes the phosphorylation of the 3’-hydroxyl group of cytidine diphosphoramidate. The resulting cofactor is very similar to the 3’-phosphoadenylyl sulfate (PAPS) that is used by many biological systems for the transfer of sulfate. Presumably 3’-phosphocytidine diphosphoramidate is used to transfer the phosphoramidate moiety to the capsule, and then methylated resulting in the final MeOPN modification. | en |
