2QIN

Stenotrophomonas maltophilia L1 Metallo-beta-Lactamase Asp-120 Cys mutant

2QIN の概要

• エントリーDOI: 10.2210/pdb2qin/pdb
• 関連するPDBエントリー: 1SML 2AIO
• 分子名称: Metallo-beta-lactamase L1, ZINC ION, MAGNESIUM ION, ... (4 entities in total)
• 機能のキーワード: metallo-beta-lactamase, hydrolase, binuclear, dinuclear
• 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: 4
• 化学式量合計: 115551.32

構造登録者

Spencer, J. (登録日: 2007-07-05, 公開日: 2007-08-14, 最終更新日: 2024-10-30)

主引用文献

Crisp, J.,Conners, R.,Garrity, J.D.,Carenbauer, A.L.,Crowder, M.W.,Spencer, J.
Structural Basis for the Role of Asp-120 in Metallo-beta-lactamases.
Biochemistry, 46:10664-10674, 2007

PubMed Abstract: Metallo-beta-lactamases (mbetals) are zinc-dependent enzymes that hydrolyze a wide range of beta-lactam antibiotics. The mbetal active site features an invariant Asp-120 that ligates one of the two metal ions (Zn2) and a metal-bridging water/hydroxide (Wat1). Previous studies show that substitutions at Asp-120 dramatically affect mbetal activity, but no consensus exists as to its role in beta-lactam turnover. Here we present crystal structures of the Asn and Cys mutants of Asp-120 of the L1 mbetal from Stenotrophomonas maltophilia. Both mutants retain a dinuclear zinc center with Wat1 present. In the essentially inactive Cys enzyme Zn2 is displaced to a more buried position relative to that in the wild-type enzyme. In the catalytically impaired Asn enzyme the coordination of Zn2 is altered, neither it nor Wat1 is coordinated by Asn-120, and the N-terminal 19 amino acids, important to cooperative interactions between subunits in the wild-type enzyme, are disordered. Comparison with the structure of L1 complexed with the hydrolyzed oxacephem moxalactam suggests that in the Cys mutant Zn2 can no longer make stabilizing interactions with anionic nitrogen species formed in the hydrolytic reaction. The diminished activity of the Asn mutant arises from a combination of loss of intersubunit interactions and impaired proton transfer to, and reduced interaction of Zn2 with, the substrate amide nitrogen. We conclude that, while interactions of Asp-120 with active site water molecules are important to proton transfer and possibly nucleophilic attack by Wat1, its primary role is to optimally position Zn2 for catalytically important interactions with the charged amide nitrogen of substrate.

PubMed: 17715946
DOI: 10.1021/bi700707u

実験手法

X-RAY DIFFRACTION (1.76 Å)