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2cla
From Proteopedia
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CRYSTAL STRUCTURE OF THE ASP-199-ASN MUTANT OF CHLORAMPHENICOL ACETYLTRANSFERASE TO 2.35 ANGSTROMS RESOLUTION. STRUCTURAL CONSEQUENCES OF DISRUPTION OF A BURIED SALT-BRIDGE
Overview
The crystal structure of the Asp-199----Asn mutant of chloramphenicol acetyltransferase (CAT) has been determined to 2.35-A resolution. In wild-type CAT Asp-199 is involved in a fully buried intrasubunit salt bridge with Arg-18, an interaction that is adjacent to the active site. Replacement of aspartate with asparagine by site-directed mutagenesis disrupts this salt bridge and causes extensive conformational changes within the active site. The imidazole group of the catalytically essential His-195 is reoriented, with the loss of interactions thought to stabilize the preferred tautomer of this residue. Arg-18 and Asn-199 form three new intersubunit interactions as a result of large side-chain torsion angle changes which cause the movement of two polypeptide loops, some residues of which are up to 20 A away from the site of the mutation. The new interactions of Arg-18 and Asn-199 compensate for the loss of the buried salt bridge and afford near-wild-type thermostability to Asn-199 CAT, albeit with a greatly reduced activity.
About this Structure
2CLA is a Single protein structure of sequence from Escherichia coli with as ligand. Active as Chloramphenicol O-acetyltransferase, with EC number 2.3.1.28 Full crystallographic information is available from OCA.
Reference
Crystal structure of the aspartic acid-199----asparagine mutant of chloramphenicol acetyltransferase to 2.35-A resolution: structural consequences of disruption of a buried salt bridge., Gibbs MR, Moody PC, Leslie AG, Biochemistry. 1990 Dec 25;29(51):11261-5. PMID:2271709
Page seeded by OCA on Thu Feb 21 16:49:49 2008
