1OME

CRYSTAL STRUCTURE OF THE OMEGA LOOP DELETION MUTANT (RESIDUES 163-178 DELETED) OF BETA-LACTAMASE FROM STAPHYLOCOCCUS AUREUS PC1

1OME の概要

• エントリーDOI: 10.2210/pdb1ome/pdb
• 分子名称: BETA-LACTAMASE, CHLORIDE ION (3 entities in total)
• 機能のキーワード: hydrolase, beta-lactamase, beta-lactam antibiotic resistance
• 由来する生物種: Staphylococcus aureus
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 57984.26

構造登録者

Banerjee, S.,Pieper, U.,Herzberg, O. (登録日: 1998-02-09, 公開日: 1998-05-27, 最終更新日: 2024-05-22)

主引用文献

Banerjee, S.,Pieper, U.,Kapadia, G.,Pannell, L.K.,Herzberg, O.
Role of the omega-loop in the activity, substrate specificity, and structure of class A beta-lactamase.
Biochemistry, 37:3286-3296, 1998

PubMed Abstract: The structure of class A beta-lactamases contains an omega-loop associated with the active site, which carries a key catalytic residue, Glu166. A 16-residue omega-loop deletion mutant of beta-lactamase from Staphylococcus aureus PC1, encompassing residues 163-178, was produced in order to examine the functional and structural role of the loop. The crystal structure was determined and refined at 2.3 A, and the kinetics of the mutant enzyme was characterized with a variety of beta-lactam antibiotics. In general, the wild-type beta-lactamase hydrolyzes penicillin compounds better than cephalosporins. In contrast, the deletion of the omega-loop led to a variant enzyme that acts only on cephalosporins, including third generation compounds. Kinetic measurements and electrospray mass spectrometry revealed that the first and third generation cephalosporins form stable acyl-enzyme complexes, except for the chromogenic cephalosporin, nitrocefin, which after acylating the enzyme undergoes hydrolysis at a 1000-fold slower rate than that with wild-type beta-lactamase. Hydrolysis of the acyl-enzyme adducts is prevented because the deletion of the omega-loop eliminates the deacylation apparatus comprising Glu166 and its associated nucleophilic water site. The crystal structure reveals that while the overall fold of the mutant enzyme is similar to that of the native beta-lactamase, local adjustments in the vicinity of the missing loop occurred. The altered beta-lactam specificity is attributed to these structural changes. In the native structure, the omega-loop restricts the conformation of a beta-strand at the edge of the active site depression. Removal of the loop provides the beta-strand with a new degree of conformational flexibility, such that it is displaced inward toward the active site space. Modeled Michaelis complexes with benzylpenicillin and cephaloridine show that the perturbed conformation of the beta-strand is inconsistent with penicillin binding because of steric clashes between the beta-lactam side chain substituent and the beta-strand. In contrast, no clashes occur upon cephalosporin binding. Recognition of third generation cephalosporins is possible because the bulky side chain substituents of the beta-lactam ring typical of these compounds can be accommodated in the space freed by the deletion of the omega-loop.

PubMed: 9521648
DOI: 10.1021/bi972127f

実験手法

X-RAY DIFFRACTION (2.3 Å)