1I5Q

CRYSTAL STRUCTURE OF THE E. COLI AMPC BETA-LACTAMASE MUTANT N152A COVALENTLY ACYLATED WITH THE INHIBITORY BETA-LACTAM, MOXALACTAM

1I5Q の概要

• エントリーDOI: 10.2210/pdb1i5q/pdb
• 関連するPDBエントリー: 1FCO 2BLS
• 分子名称: BETA-LACTAMASE, (2R)-2-[(1R)-1-{[(2S)-2-carboxy-2-(4-hydroxyphenyl)acetyl]amino}-1-methoxy-2-oxoethyl]-5-methylidene-5,6-dihydro-2H-1,3-oxazine-4-carboxylic acid (3 entities in total)
• 機能のキーワード: cephalosporinase, beta-lactamase, serine hydrolase, hydrolase
• 由来する生物種: Escherichia coli
• 細胞内の位置: Periplasm: P00811
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 79902.48

構造登録者

Trehan, I.,Beadle, B.M.,Shoichet, B.K. (登録日: 2001-02-28, 公開日: 2001-06-20, 最終更新日: 2024-11-13)

主引用文献

Trehan, I.,Beadle, B.M.,Shoichet, B.K.
Inhibition of AmpC beta-lactamase through a destabilizing interaction in the active site.
Biochemistry, 40:7992-7999, 2001

PubMed Abstract: Beta-lactamases hydrolyze beta-lactam antibiotics, including penicillins and cephalosporins; these enzymes are the most widespread resistance mechanism to these drugs and pose a growing threat to public health. beta-Lactams that contain a bulky 6(7)alpha substituent, such as imipenem and moxalactam, actually inhibit serine beta-lactamases and are widely used for this reason. Although mutant serine beta-lactamases have arisen that hydrolyze beta-lactamase resistant beta-lactams (e.g., ceftazidime) or avoid mechanism-based inhibitors (e.g., clavulanate), mutant serine beta-lactamases have not yet arisen in the clinic with imipenemase or moxalactamase activity. Structural and thermodynamic studies suggest that the 6(7)alpha substituents of these inhibitors form destabilizing contacts within the covalent adduct with the conserved Asn152 in class C beta-lactamases (Asn132 in class A beta-lactamases). This unfavorable interaction may be crucial to inhibition. To test this destabilization hypothesis, we replaced Asn152 with Ala in the class C beta-lactamase AmpC from Escherichia coli and examined the mutant enzyme's thermodynamic stability in complex with imipenem and moxalactam. Consistent with the hypothesis, the Asn152 --> Ala substitution relieved 0.44 and 1.10 kcal/mol of strain introduced by imipenem and moxalactam, respectively, relative to the wild-type complexes. However, the kinetic efficiency of AmpC N152A was reduced by 6300-fold relative to that of the wild-type enzyme. To further investigate the inhibitor's interaction with the mutant enzyme, the X-ray crystal structure of moxalactam in complex with N152A was determined to a resolution of 1.83 A. Moxalactam in the mutant complex is significantly displaced from its orientation in the wild-type complex; however, moxalactam does not adopt an orientation that would restore competence for hydrolysis. Although Asn152 forces beta-lactams with 6(7)alpha substituents out of a catalytically competent configuration, making them inhibitors, the residue is essential for orienting beta-lactam substrates and cannot simply be replaced with a much smaller residue to restore catalytic activity. Designing beta-lactam inhibitors that interact unfavorably with this conserved residue when in the covalent adduct merits further investigation.

PubMed: 11434768
DOI: 10.1021/bi010641m

実験手法

X-RAY DIFFRACTION (1.83 Å)