Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-08T07:58:15.776Z Has data issue: false hasContentIssue false

The complexed structure and antimicrobial activity of a non-β-lactam inhibitor of AmpC β-lactamase

Published online by Cambridge University Press:  01 November 1999

RACHEL A. POWERS
Affiliation:
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, Illinois 60611
JESÚS BLÁZQUEZ
Affiliation:
Servicio de Microbiología, Hospital Ramón y Cajal, Ctra. Colmenar Km 9.100, 28034, Madrid, Spain
G. SCOTT WESTON
Affiliation:
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, Illinois 60611 Present address: Computational Design and Informatics, ArQule, Inc., 200 Boston Avenue, Medford, Massachusetts 02155.
MARÍA-ISABEL MOROSINI
Affiliation:
Servicio de Microbiología, Hospital Ramón y Cajal, Ctra. Colmenar Km 9.100, 28034, Madrid, Spain
FERNANDO BAQUERO
Affiliation:
Servicio de Microbiología, Hospital Ramón y Cajal, Ctra. Colmenar Km 9.100, 28034, Madrid, Spain
BRIAN K. SHOICHET
Affiliation:
Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, Illinois 60611
Get access

Abstract

β-Lactamases are the major resistance mechanism to β-lactam antibiotics and pose a growing threat to public health. Recently, bacteria have become resistant to β-lactamase inhibitors, making this problem pressing. In an effort to overcome this resistance, non-β-lactam inhibitors of β-lactamases were investigated for complementarity to the structure of AmpC β-lactamase from Escherichia coli. This led to the discovery of an inhibitor, benzo(b)thiophene-2-boronic acid (BZBTH2B), which inhibited AmpC with a Ki of 27 nM. This inhibitor is chemically dissimilar to β-lactams, raising the question of what specific interactions are responsible for its activity. To answer this question, the X-ray crystallographic structure of BZBTH2B in complex with AmpC was determined to 2.25 Å resolution. The structure reveals several unexpected interactions. The inhibitor appears to complement the conserved, R1-amide binding region of AmpC, despite lacking an amide group. Interactions between one of the boronic acid oxygen atoms, Tyr150, and an ordered water molecule suggest a mechanism for acid/base catalysis and a direction for hydrolytic attack in the enzyme catalyzed reaction. To investigate how a non-β-lactam inhibitor would perform against resistant bacteria, BZBTH2B was tested in antimicrobial assays. BZBTH2B significantly potentiated the activity of a third-generation cephalosporin against AmpC-producing resistant bacteria. This inhibitor was unaffected by two common resistance mechanisms that often arise against β-lactams in conjunction with β-lactamases. Porin channel mutations did not decrease the efficacy of BZBTH2B against cells expressing AmpC. Also, this inhibitor did not induce expression of AmpC, a problem with many β-lactams. The structure of the BZBTH2B/AmpC complex provides a starting point for the structure-based elaboration of this class of non-β-lactam inhibitors.

Type
Research Article
Copyright
© 1999 The Protein Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)