title: PBP5, PBP6 and DacD play different roles in intrinsic β-lactam resistance of Escherichia coli.
abstract: Escherichia coli PBP5, PBP6 and DacD, encoded by dacA, dacC and dacD, respectively, share substantial amino acid identity and together constitute ~50 % of the total penicillin-binding proteins of E. coli. PBP5 helps maintain intrinsic β-lactam resistance within the cell. To test if PBP6 and DacD play simlar roles, we deleted dacC and dacD individually, and dacC in combination with dacA, from E. coli 2443 and compared β-lactam sensitivity of the mutants and the parent strain. β-Lactam resistance was complemented by wild-type, but not dd-carboxypeptidase-deficient PBP5, confirming that enzymic activity of PBP5 is essential for β-lactam resistance. Deletion of dacC and expression of PBP6 during exponential or stationary phase did not alter β-lactam resistance of a dacA mutant. Expression of DacD during mid-exponential phase partially restored β-lactam resistance of the dacA mutant. Therefore, PBP5 dd-carboxypeptidase activity is essential for intrinsic β-lactam resistance of E. coli and DacD can partially compensate for PBP5 in this capacity, whereas PBP6 cannot.
authors: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal PIN-721302, India.
authors: Sujoy Kumar
authors: SK
authors: Sarkar
authors: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal PIN-721302, India.
authors: Mouparna
authors: M
authors: Dutta
authors: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal PIN-721302, India.
authors: Chiranjit
authors: C
authors: Chowdhury
authors: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal PIN-721302, India.
authors: Akash
authors: A
authors: Kumar
authors: Department of Biotechnology, Indian Institute of Technology, Kharagpur, West Bengal PIN-721302, India.
authors: Anindya S
authors: AS
authors: Ghosh
mesh_terms: D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D009154:Mutation / Q000235:genetics; D046915:Penicillin-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase; D018440:beta-Lactam Resistance / Q000235:genetics
chemical_list: C569174:DacD protein, E coli; D029968:Escherichia coli Proteins; C569173:PBP5 protein, E coli; D046915:Penicillin-Binding Proteins; C569172:DacC protein, E coli; D046929:Serine-Type D-Ala-D-Ala Carboxypeptidase