title: dacD, an Escherichia coli gene encoding a novel penicillin-binding protein (PBP6b) with DD-carboxypeptidase activity.
abstract: In the course of a study of genes located at min 44 of the Escherichia coli genome, we identified an open reading frame with the capacity to encode a 43-kDa polypeptide whose predicted amino acid sequence is strikingly similar to those of the well-known DD-carboxipeptidases penicillin-binding proteins PBP5 and PBP6. The gene product was shown to bind [3H]benzylpenicillin and to have DD-carboxypeptidase activity on pentapeptide muropeptides in vivo. Therefore, we called the protein PBP6b and the gene dacD. As with other E. coli DD-carboxypeptidases, PBP6b is not essential for cell growth. A quadruple dacA dacB dacC dacD mutant was constructed and shown to grow as well as its isogenic wild-type strain, indicating that the loss of any known PBP-associated DD-carboxypeptidase activity is not deleterious for E. coli. We also identified the homologous gene of dacD in Salmonella typhimurium as one of the components of the previously described phsBCDEF gene cluster.
authors.affiliation: Unidad de Genética Molecular, Hospital Ramón y Cajal, Madrid, Spain.
authors.forename: M R
authors.initials: MR
authors.lastname: Baquero
authors.forename: M
authors.initials: M
authors.lastname: Bouzon
authors.forename: J C
authors.initials: JC
authors.lastname: Quintela
authors.forename: J A
authors.initials: JA
authors.lastname: Ayala
authors.forename: F
authors.initials: F
authors.lastname: Moreno
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D029968:Escherichia coli Proteins; D006602:Hexosyltransferases; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics* / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010458:Peptidyl Transferases; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010455:Peptides; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; C478706:penicillin-binding protein 4, E coli; D002267:Muramoylpentapeptide Carboxypeptidase