3mqg

Publication Abstract from PubMed

The pathogenic bacteria Pseudomonas aeruginosa and Bordetella pertussis contain in their outer membranes the rare sugar 2,3-diacetamido-2,3-dideoxy-d-mannuronic acid. Five enzymes are required for the biosynthesis of this sugar starting from UDP-N-acetylglucosamine. One of these, referred to as WlbB, is an N-acetyltransferase that converts UDP-2-acetamido-3-amino-2,3-dideoxy-d-glucuronic acid (UDP-GlcNAc3NA) to UDP-2,3-diacetamido-2,3-dideoxy-d-glucuronic acid (UDP-GlcNAc3NAcA). Here we report the three-dimensional structure of WlbB from Bordetella petrii. For this analysis, two ternary structures were determined to 1.43 A resolution: one in which the protein was complexed with acetyl-CoA and UDP and the second in which the protein contained bound CoA and UDP-GlcNAc3NA. WlbB adopts a trimeric quaternary structure and belongs to the LbetaH superfamily of N-acyltransferases. Each subunit contains 27 beta-strands, 23 of which form the canonical left-handed beta-helix. There are only two hydrogen bonds that occur between the protein and the GlcNAc3NA moiety, one between O(delta1) of Asn 84 and the sugar C-3' amino group and the second between the backbone amide group of Arg 94 and the sugar C-5' carboxylate. The sugar C-3' amino group is ideally positioned in the active site to attack the si face of acetyl-CoA. Given that there are no protein side chains that can function as general bases within the GlcNAc3NA binding pocket, a reaction mechanism is proposed for WlbB whereby the sulfur of CoA ultimately functions as the proton acceptor required for catalysis.

Molecular Structure of WlbB, a Bacterial N-Acetyltransferase Involved in the Biosynthesis of 2,3-Diacetamido-2,3-dideoxy-d-mannuronic Acid .,Thoden JB, Holden HM Biochemistry. 2010 Jun 8;49(22):4644-53. PMID:20433200^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.