Glycosyl transferase activity of the Escherichia coli penicillin-binding protein 1b: specificity profile for the substrate.
The glycosyl transferase of the Escherichia coli bifunctional penicillin-binding protein (PBP) 1b catalyzes the assembly of lipid-transported N-acetylglucosaminyl-beta-1,4-N-acetylmuramoyl-L-Ala-gamma-D-Glu-meso-A2pm-D-Ala-D-Ala units (lipid II) into linear peptidoglycan chains. These units are linked, at C1 of N-acetylmuramic acid (MurNAc), to a C55 undecaprenyl pyrophosphate. In an in vitro assay, lipid II functions both as a glycosyl donor and as a glycosyl acceptor substrate. Using substrate analogues, it is suggested that the specificity of the enzyme for the glycosyl donor substrate differs from that for the acceptor. The donor substrate requires the presence of both N-acetylglucosamine (GlcNAc) and MurNAc and a reactive group on C1 of the MurNAc and does not absolutely require the lipid chain which can be replaced by uridine. The enzyme appears to prefer an acceptor substrate containing a polyprenyl pyrophosphate on C1 of the MurNAc sugar. The problem of glycan chain elongation that presumably proceeds by the repetitive addition of disaccharide peptide units at their reducing end is discussed.
Centre d'Ingénierie des Protéines, Institut de Chimie B6a, Université de Liège, B-4000 Sart Tilman, Belgium.
Claudine
C
Fraipont
Frédéric
F
Sapunaric
Astrid
A
Zervosen
Geneviève
G
Auger
Bart
B
Devreese
Thierry
T
Lioux
Didier
D
Blanot
Dominique
D
Mengin-Lecreulx
Piet
P
Herdewijn
Jozef
J
Van Beeumen
Jean-Marie
JM
Frère
Martine
M
Nguyen-Distèche
D002240:Carbohydrate Sequence; D002384:Catalysis; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D016695:Glycosyltransferases / Q000378:metabolism*; D008969:Molecular Sequence Data; D046915:Penicillin-Binding Proteins / Q000378:metabolism*; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism*; D046928:Peptidoglycan Glycosyltransferase / Q000378:metabolism*; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase / Q000378:metabolism*; D013379:Substrate Specificity
D029968:Escherichia coli Proteins; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D016695:Glycosyltransferases; D046928:Peptidoglycan Glycosyltransferase; C478681:penicillin-binding protein 1B, E coli; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase