Crystal Structure of a Deacylation-Defective Mutant of Penicillin-Binding Protein 5 at 2.3-A ResolutionDavies, C., White, S.W., Nicholas, R.A.
(2001) J.Biol.Chem. 276: 616
- PubMed: 10967102
- DOI: 10.1074/jbc.M004471200
- PubMed Abstract:
- An Amino Acid Substitution that Blocks the Deacylation Step in the Enzyme Mechanism of Penicillin-Binding Protein 5 of Escherichia Coli
Broome-Smith, J.,Spratt, B.G.
(1984) FEBS Lett. 165: 185
- Relations between Beta-Lactamases and Penicillin-Binding Proteins: Beta-Lactamase Activity of Penicillin-Binding Protein 5 from Escherichia Coli
Nicholas, R.A.,Strominger, J.L.
(1988) Rev.Infect.Dis. 10: 733
Penicillin-binding protein 5 (PBP 5) of Escherichia coli functions as a d-alanine carboxypeptidase, cleaving the C-terminal d-alanine residue from cell wall peptides. Like all PBPs, PBP 5 forms a covalent acyl-enzyme complex with beta-lactam antibiot ...
Penicillin-binding protein 5 (PBP 5) of Escherichia coli functions as a d-alanine carboxypeptidase, cleaving the C-terminal d-alanine residue from cell wall peptides. Like all PBPs, PBP 5 forms a covalent acyl-enzyme complex with beta-lactam antibiotics; however, PBP 5 is distinguished by its high rate of deacylation of the acyl-enzyme complex (t(12) approximately 9 min). A Gly-105 --> Asp mutation in PBP 5 markedly impairs this beta-lactamase activity (deacylation), with only minor effects on acylation, and promotes accumulation of a covalent complex with peptide substrates. To gain further insight into the catalytic mechanism of PBP 5, we determined the three-dimensional structure of the G105D mutant form of soluble PBP 5 (termed sPBP 5') at 2.3 A resolution. The structure is composed of two domains, a penicillin binding domain with a striking similarity to Class A beta-lactamases (TEM-1-like) and a domain of unknown function. In addition, the penicillin-binding domain contains an active site loop spatially equivalent to the Omega loop of beta-lactamases. In beta-lactamases, the Omega loop contains two amino acids involved in catalyzing deacylation. This similarity may explain the high beta-lactamase activity of wild-type PBP 5. Because of the low rate of deacylation of the G105D mutant, visualization of peptide substrates bound to the active site may be possible.
School of Biological Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom.