title: Crystal structure of MltA from Escherichia coli reveals a unique lytic transglycosylase fold.
abstract: Lytic transglycosylases are bacterial enzymes involved in the maintenance and growth of the bacterial cell-wall peptidoglycan. They cleave the beta-(1,4)-glycosidic bonds in peptidoglycan forming non-reducing 1,6-anhydromuropeptides. The crystal structure of the lytic transglycosylase MltA from Escherichia coli without a membrane anchor was solved at 2.0A resolution. The enzyme has a fold completely different from those of the other known lytic transglycosylases. It contains two domains, the largest of which has a double-psi beta-barrel fold, similar to that of endoglucanase V from Humicola insolens. The smaller domain also has a beta-barrel fold topology, which is weakly related to that of the RNA-binding domain of ribosomal proteins L25 and TL5. A large groove separates the two domains, which can accommodate a glycan strand, as shown by molecular modelling. Several conserved residues, one of which is in a position equivalent to that of the catalytic acid of the H.insolens endoglucanase, flank this putative substrate-binding groove. Mutation of this residue, Asp308, abolished all activity of the enzyme, supporting the direct participation of this residue in catalysis.
authors.affiliation: Laboratory of Biophysical Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Karin E
authors.initials: KE
authors.lastname: van Straaten
authors.forename: Bauke W
authors.initials: BW
authors.lastname: Dijkstra
authors.forename: Waldemar
authors.initials: W
authors.lastname: Vollmer
authors.forename: Andy-Mark W H
authors.initials: AM
authors.lastname: Thunnissen
mesh_terms: D000595:Amino Acid Sequence; D001433:Bacteriolysis / Q000502:physiology*; D001665:Binding Sites; D020134:Catalytic Domain; D002480:Cellulase / Q000235:genetics; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D016695:Glycosyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D010457:Peptidoglycan / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017385:Sequence Homology
chemical_list: D010457:Peptidoglycan; D010940:Plant Proteins; C076873:barwin protein, Hordeum vulgare; D016695:Glycosyltransferases; C085441:MltA protein, bacteria; D002480:Cellulase