4lxu

Publication Abstract from PubMed

The O-antigens, which are components of the outer membranes of Gram-negative bacteria, are responsible for the wide species variations seen in nature and are thought to play a role in bacterial virulence. They often contain unusual dideoxysugars such as 3,6-dideoxy-3-formamido-D-glucose (Qui3NFo). Here we describe a structural and functional investigation of the protein C8J_1081 from Campylobacter jejuni 81116, which is involved in the biosynthesis of Qui3NFo. Specifically the enzyme, hereafter referred to as WlaRD, catalyzes the N-formylation of dTDP-3,6-dideoxy-3-amino-D-glucose (dTDP-Qui3N) using N10-formyltetrahydrofolate as the carbon source. For this investigation, seven X-ray structures of WlaRD, in complexes with various dTDP-linked sugars and cofactors, were determined to resolutions of 1.9 A or better. One of the models, with bound N10-formyltetrahydrofolate and dTDP, represents the first glimpse of an N-formyltransferase with its natural cofactor. Another model contains the reaction products, tetrahydrofolate and dTDP-Qui3NFo. In combination, the structures provide snapshots of the WlaRD active site before and after catalysis. On the basis of these structures, three amino acid residues were targeted for study: Asn 94, His 96, and Asp 132. Mutations of any of these residues resulted in a complete loss of enzymatic activity. Given the position of His 96 in the active site, it can be postulated that it functions as the active site base to remove the proton from the sugar amino group as it attacks the carbonyl carbon of the N-10 formyl group of the cofactor. Enzyme assays demonstrate that WlaRD is also capable of utilizing dTDP-3,6-dideoxy-3-amino-D-galactose (dTDP-Fuc3N) as a substrate, albeit at a much reduced catalytic efficiency.

The Structure of a Sugar N-Formyltransferase from Campylobacter jejuni.,Thoden JB, Goneau MF, Gilbert M, Holden HM Biochemistry. 2013 Jul 30. PMID:23898784^[1]

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