title: NMR structure of Citrobacter freundii AmpD, comparison with bacteriophage T7 lysozyme and homology with PGRP domains.
abstract: AmpD is a bacterial amidase involved in the recycling of cell-wall fragments in Gram-negative bacteria. Inactivation of AmpD leads to derepression of beta-lactamase expression, presenting a major pathway for the acquisition of constitutive antibiotic resistance. Here, we report the NMR structure of AmpD from Citrobacter freundii (PDB accession code 1J3G). A deep substrate-binding pocket explains the observed specificity for low molecular mass substrates. The fold is related to that of bacteriophage T7 lysozyme. Both proteins bind zinc at a conserved site and require zinc for amidase activity, although the enzymatic mechanism seems to differ in detail. The structure-based sequence alignment identifies conserved features that are also conserved in the eukaryotic peptidoglycan recognition protein (PGRP) domains, including the zinc-coordination site in several of them. PGRP domains thus belong to the same fold family and, where zinc-binding residues are conserved, may have amidase activity. This hypothesis is supported by the observation that human serum N-acetylmuramyl-L-alanine amidase seems to be identical with a soluble form of human PGRP-L.
authors.affiliation: Department of Medical Biochemistry, Karolinska Institute, S-17177 Stockholm, Sweden.
authors.forename: Edvards
authors.initials: E
authors.lastname: Liepinsh
authors.forename: Catherine
authors.initials: C
authors.lastname: Généreux
authors.forename: Dominique
authors.initials: D
authors.lastname: Dehareng
authors.forename: Bernard
authors.initials: B
authors.lastname: Joris
authors.forename: Gottfried
authors.initials: G
authors.lastname: Otting
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D017123:Bacteriophage T7 / Q000201:enzymology*; D002352:Carrier Proteins / Q000737:chemistry*; D016971:Citrobacter freundii / Q000737:chemistry*; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics; D005057:Eukaryotic Cells / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D009238:N-Acetylmuramoyl-L-alanine Amidase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013379:Substrate Specificity; D015032:Zinc / Q000032:analysis
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; C118897:peptidoglycan recognition protein; C062460:AmpD protein, Bacteria; D009238:N-Acetylmuramoyl-L-alanine Amidase; D015032:Zinc