Role of Ser216 in the mechanism of action of membrane-bound lytic transglycosylase B: further evidence for substrate-assisted catalysis

FEBS Lett. 2007 Oct 16;581(25):4988-92. doi: 10.1016/j.febslet.2007.09.037. Epub 2007 Sep 29.

Abstract

Lytic transglycosylases cleave the beta-(1-->4)-glycosidic bond in the bacterial cell wall heteropolymer peptidoglycan between the N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) residues with the concomitant formation of a 1,6-anhydromuramoyl residue. Based on sequence alignments, Ser216 in Pseudomonas aeruginosa membrane-bound lytic transglycosylase B (MltB) was targeted for replacement with alanine to delineate its role in the enzyme's mechanism of action. The specific activity of the Ser216-->Ala MltB derivative was less than 12% of that for the wild-type enzyme, while its substrate binding affinity remained virtually unaltered. These data are in agreement with a role of Ser216 in orienting the N-acetyl group on MurNAc at the -1 subsite of MltB for its participation in a substrate-assisted mechanism of action.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Binding Sites
  • Catalysis
  • Glycosyltransferases / chemistry*
  • Glycosyltransferases / genetics
  • Kinetics
  • Membrane Proteins / chemistry*
  • Membrane Proteins / genetics
  • Mutagenesis, Site-Directed
  • Peptidoglycan / chemistry
  • Peptidoglycan / metabolism
  • Pseudomonas aeruginosa / enzymology
  • Serine / chemistry*

Substances

  • Bacterial Proteins
  • Membrane Proteins
  • Peptidoglycan
  • Serine
  • Glycosyltransferases