1or0
From Proteopedia
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Crystal Structures of Glutaryl 7-Aminocephalosporanic Acid Acylase: Insight into Autoproteolytic Activation
Overview
Glutaryl 7-aminocephalosporanic acid acylase (GCA, EC 3.5.1.11) is a, member of N-terminal nucleophile (Ntn) hydrolases. The native enzyme is an, (alpha beta)(2) heterotetramer originated from an enzymatically inactive, precursor of a single polypeptide. The activation of precursor GCA, consists of primary and secondary autoproteolytic cleavages, generating a, terminal residue with both a nucleophile and a base and releasing a nine, amino acid spacer peptide. We have determined the crystal structures of, the recombinant selenomethionyl native and S170A mutant precursor from, Pseudomonas sp. strain GK16. Precursor activation is likely triggered by, conformational constraints within the spacer peptide, probably inducing a, peptide flip. Autoproteolytic site solvent molecules, which have been, trapped in a hydrophobic environment by the spacer peptide, may play a, role as a general base for nucleophilic attack. The activation results in, building up a catalytic triad composed of Ser170/His192/Glu624. However, the triad is not linked to the usual hydroxyl but the free alpha-amino, group of the N-terminal serine residue of the native GCA. Mutagenesis and, structural data support the notion that the stabilization of a transient, hydroxazolidine ring during autoproteolysis would be critical during the N, --> O acyl shift. The autoproteolytic activation mechanism for GCA is, described.
About this Structure
1OR0 is a Protein complex structure of sequences from Pseudomonas sp. se83 with EDO as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structures of glutaryl 7-aminocephalosporanic acid acylase: insight into autoproteolytic activation., Kim JK, Yang IS, Rhee S, Dauter Z, Lee YS, Park SS, Kim KH, Biochemistry. 2003 Apr 15;42(14):4084-93. PMID:12680762
Page seeded by OCA on Tue Nov 20 23:07:08 2007
