1xpb
From Proteopedia
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STRUCTURE OF BETA-LACTAMASE TEM1
Overview
beta-Lactamases are bacterial enzymes which catalyse the hydrolysis of the, beta-lactam ring of penicillins, cephalosporins and related compounds, thus inactivating these antibiotics. The crystal structure of the TEM1, beta-lactamase has been determined at 1.9 A resolution by the, molecular-replacement method, using the atomic coordinates of two, homologous beta-lactamase refined structures which show about 36% strict, identity in their amino-acid sequences and 1.96 A r.m.s. deviation between, equivalent Calpha atoms. The TEM1 enzyme crystallizes in space group, P2(1)2(1)2(1) and there is one molecule per asymmetric unit. The structure, was refined by simulated annealing to an R-factor of 15.6% for 15 086, reflections with I >/= 2sigma(I) in the resolution range 5.0-1.9 A. The, final crystallographic structure contains 263 amino-acid residues, one, sulfate anion in the catalytic cleft and 135 water molecules per, asymmetric unit. The folding is very similar to that of the other known, class A beta-lactamases. It consists of two domains, the first is formed, by a five-stranded beta-sheet covered by three alpha-helices on one face, and one alpha-helix on the other, the second domain contains mainly, alpha-helices. The catalytic cleft is located at the interface between the, two domains. We also report the crystallographic study of the TEM S235A, mutant. This mutation of an active-site residue specifically decreases the, acylation rate of cephalosporins. This TEM S235A mutant crystallizes under, the same conditions as the wild-type protein and its structure was refined, at 2.0 A resolution with an R value of 17.6%. The major modification is, the appearance of a water molecule near the mutated residue, which is, incompatible with the OG 235 present in the wild-type enzyme, and causes, very small perturbations in the interaction network in the active site.
About this Structure
1XPB is a Single protein structure of sequence from Escherichia coli with SO4 as ligand. Active as Beta-lactamase, with EC number 3.5.2.6 Structure known Active Site: ACT. Full crystallographic information is available from OCA.
Reference
TEM1 beta-lactamase structure solved by molecular replacement and refined structure of the S235A mutant., Fonze E, Charlier P, To'th Y, Vermeire M, Raquet X, Dubus A, Frere JM, Acta Crystallogr D Biol Crystallogr. 1995 Sep 1;51(Pt 5):682-94. PMID:15299797
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