1SML

METALLO BETA LACTAMASE L1 FROM STENOTROPHOMONAS MALTOPHILIA

1SML の概要

• エントリーDOI: 10.2210/pdb1sml/pdb
• 分子名称: PROTEIN (PENICILLINASE), ZINC ION (3 entities in total)
• 機能のキーワード: metallo-beta-lactamase, antibiotic resistance, binuclear zinc, hydrolase
• 由来する生物種: Stenotrophomonas maltophilia
• 細胞内の位置: Periplasm (Potential): P52700
• タンパク質・核酸の鎖数: 1
• 化学式量合計: 28871.27

構造登録者

Ullah, J.H.,Walsh, T.R.,Taylor, I.A.,Emery, D.C.,Verma, C.S.,Gamblin, S.J.,Spencer, J. (登録日: 1998-09-22, 公開日: 1999-09-20, 最終更新日: 2024-11-20)

主引用文献

Ullah, J.H.,Walsh, T.R.,Taylor, I.A.,Emery, D.C.,Verma, C.S.,Gamblin, S.J.,Spencer, J.
The crystal structure of the L1 metallo-beta-lactamase from Stenotrophomonas maltophilia at 1.7 A resolution.
J.Mol.Biol., 284:125-136, 1998

PubMed Abstract: The structure of the L1 metallo-beta-lactamase from the opportunistic pathogen Stenotrophomonas maltophilia has been determined at 1.7 A resolution by the multiwavelength anomalous dispersion (MAD) approach exploiting both the intrinsic binuclear zinc centre and incorporated selenomethionine residues. L1 is unique amongst all known beta-lactamases in that it exists as a tetramer. The protein exhibits the alphabeta/betaalpha fold found only in the metallo-beta-lactamases and displays several unique features not previously observed in these enzymes. These include a disulphide bridge and two substantially elongated loops connected to the active site of the enzyme. Two closely spaced zinc ions are bound at the active site with tetrahedral (Zn1) and trigonal bipyramidal (Zn2) co-ordination, respectively; these are bridged by a water molecule which we propose acts as the nucleophile in the hydrolytic reaction. Ligation of the second zinc ion involves both residues and geometry which have not been previously observed in the metallo-beta-lactamases. Simulated binding of the substrates ampicillin, ceftazidime and imipenem suggests that the substrate is able to bind to the enzyme in a variety of different conformations whose common features are direct interactions of the beta-lactam carbonyl oxygen and nitrogen with the zinc ions and of the beta-lactam carboxylate with Ser187. We describe a catalytic mechanism whose principal features are a nucleophilic attack of the bridging water on the beta-lactam carbonyl carbon, electrostatic stabilisation of a negatively charged tetrahedral transition state and protonation of the beta-lactam nitrogen by a second water molecule co-ordinated by Zn2. Further, we propose that direct metal:substrate interactions provide a substantial contribution to substrate binding and that this may explain the lack of specificity which is a feature of this class of enzyme.

PubMed: 9811546
DOI: 10.1006/jmbi.1998.2148

実験手法

X-RAY DIFFRACTION (1.7 Å)