skip to main content

Title: Biochemical and Structural Analysis of Inhibitors Targeting the ADC-7 Cephalosporinase of Acinetobacter baumannii

β-Lactam resistance in Acinetobacter baumannii presents one of the greatest challenges to contemporary antimicrobial chemotherapy. Much of this resistance to cephalosporins derives from the expression of the class C β-lactamase enzymes, known as Acinetobacter-derived cephalosporinases (ADCs). Currently, β-lactamase inhibitors are structurally similar to β-lactam substrates and are not effective inactivators of this class C cephalosporinase. Herein, two boronic acid transition state inhibitors (BATSIs S02030 and SM23) that are chemically distinct from β-lactams were designed and tested for inhibition of ADC enzymes. BATSIs SM23 and S02030 bind with high affinity to ADC-7, a chromosomal cephalosporinase from Acinetobacter baumannii (Ki = 21.1 ± 1.9 nM and 44.5 ± 2.2 nM, respectively). The X-ray crystal structures of ADC-7 were determined in both the apo form (1.73 Å resolution) and in complex with S02030 (2.0 Å resolution). In the complex, S02030 makes several canonical interactions: the O1 oxygen of S02030 is bound in the oxyanion hole, and the R1 amide group makes key interactions with conserved residues Asn152 and Gln120. In addition, the carboxylate group of the inhibitor is meant to mimic the C3/C4 carboxylate found in β-lactams. The C3/C4 carboxylate recognition site in class C enzymes is comprised of Asn346 and Arg349 (AmpCmore » numbering), and these residues are conserved in ADC-7. Interestingly, in the ADC-7/S02030 complex, the inhibitor carboxylate group is observed to interact with Arg340, a residue that distinguishes ADC-7 from the related class C enzyme AmpC. A thermodynamic analysis suggests that ΔH driven compounds may be optimized to generate new lead agents. In conclusion, the ADC-7/BATSI complex provides insight into recognition of non-β-lactam inhibitors by ADC enzymes and offers a starting point for the structure-based optimization of this class of novel β-lactamase inhibitors against a key resistance target.« less
Authors:
 [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [3] ;  [2] ;  [1]
  1. Grand Valley State Univ., Allendale, MI (United States). Dept. of Chemistry
  2. Louis Stokes Cleveland Dept. of Veterans Affairs Medical Center, Cleveland, OH (United States); Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Medicine, Pharmacology, Molecular Biology and Microbiology
  3. Univ. of Modena and Reggio Emilia, Modena (Italy). Dept. of Life Sciences
Publication Date:
OSTI Identifier:
1168844
Grant/Contract Number:
AC02-06CH11357; 085P1000817; R01 AI100560; R01 AI063517
Type:
Accepted Manuscript
Journal Name:
Biochemistry
Additional Journal Information:
Journal Volume: 53; Journal Issue: 48; Journal ID: ISSN 0006-2960
Publisher:
American Chemical Society (ACS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org:
USDOE Office of Science (SC); National Institutes of Health (NIH)
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 60 APPLIED LIFE SCIENCES