3bfp

From Proteopedia

Revision as of 15:29, 6 February 2008

Crystal Structure of apo-PglD from Campylobacter jejuni

Overview

Campylobacter jejuni is highly unusual among bacteria in forming N-linked, glycoproteins. The heptasaccharide produced by its pgl system is attached, to protein Asn through its terminal 2,4-diacetamido-2,4,6-trideoxy-d-Glc, (QuiNAc4NAc or N,N'-diacetylbacillosamine) moiety. The crucial, last part, of this sugar's synthesis is the acetylation of, UDP-2-acetamido-4-amino-2,4,6-trideoxy-d-Glc by the enzyme PglD, with, acetyl-CoA as a cosubstrate. We have determined the crystal structures of, PglD in CoA-bound and unbound forms, refined to 1.8 and 1.75 A resolution, respectively. PglD is a trimer of subunits each comprised of two domains, an N-terminal alpha/beta-domain and a C-terminal left-handed beta-helix., Few structural differences accompany CoA binding, except in the C-terminal, region following the beta-helix (residues 189-195), which adopts an, extended structure in the unbound form and folds to extend the beta-helix, upon binding CoA. Computational molecular docking suggests a different, mode of nucleotide-sugar binding with respect to the acetyl-CoA donor, with the molecules arranged in an "L-shape", compared with the "in-line", orientation in related enzymes. Modeling indicates that the oxyanion, intermediate would be stabilized by the NH group of Gly143', with His125', the most likely residue to function as a general base, removing H+ from, the amino group prior to nucleophilic attack at the carbonyl carbon of, acetyl-CoA. Site-specific mutations of active site residues confirmed the, importance of His125', Glu124', and Asn118. We conclude that Asn118 exerts, its function by stabilizing the intricate hydrogen bonding network within, the active site and that Glu124' may function to increase the pKa of the, putative general base, His125'.

About this Structure

3BFP is a Single protein structure of sequence from Campylobacter jejuni with as ligand. Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Structure and Active Site Residues of PglD, an N-Acetyltransferase from the Bacillosamine Synthetic Pathway Required for N-Glycan Synthesis in Campylobacter jejuni(,)., Rangarajan ES, Ruane KM, Sulea T, Watson DC, Proteau A, Leclerc S, Cygler M, Matte A, Young NM, Biochemistry. 2008 Jan 17;. PMID:18198901

Page seeded by OCA on Wed Feb 6 17:29:35 2008