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1hd8

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Revision as of 14:06, 18 December 2007 by OCA (Talk | contribs)
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Image:1hd8.jpg

1hd8, resolution 2.3Å

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CRYSTAL STRUCTURE OF A DEACYLATION-DEFECTIVE MUTANT OF PENICILLIN-BINDING PROTEIN 5 AT 2.3 A RESOLUTION

Overview

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.

About this Structure

1HD8 is a Single protein structure of sequence from Escherichia coli. Active as Serine-type D-Ala-D-Ala carboxypeptidase, with EC number 3.4.16.4 Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Crystal structure of a deacylation-defective mutant of penicillin-binding protein 5 at 2.3-A resolution., Davies C, White SW, Nicholas RA, J Biol Chem. 2001 Jan 5;276(1):616-23. PMID:10967102

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