1
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Fung YH, Kong WP, Leung ASL, Du R, So PK, Wong WL, Leung YC, Chen YW, Wong KY. NDM-1 Zn1-binding residue His116 plays critical roles in antibiotic hydrolysis. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140833. [PMID: 35944887 DOI: 10.1016/j.bbapap.2022.140833] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/28/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
Bacteria expressing NDM-1 have been labeled as superbugs because it confers upon them resistance to a broad range of β-lactam antibiotics. The enzyme has a di‑zinc active centre, with the Zn2 site extensively studied. The roles of active-site Zn1 ligand residues are, however, still not fully understood. We carried out structure-function studies using the mutants, H116A, H116N, and H116Q. Zinc content analysis showed that Zn1 binding was weakened by 40 to 60% in the H116 mutants. The enzymatic-activity studies showed that the lower hydrolysis rates were mainly caused by their weaker substrate binding. The catalytic efficiency (kcat/Km) of the mutants followed the order: WT > > H116Q (decreased by 4-20 fold) > H116A (decreased by 20-700 fold) ≥ H116N (decreased by 6-800 fold). The maximum effect was observed on H116N against penicillin G, whereas ampicillin was not hydrolyzed at all. The fold-increase of Km values, which informs the weakening of substrate binding, were: H116A by 5-45 fold; H116N by 6-100 fold; H116Q by 2-10 fold. Molecular dynamics simulations suggested that the Zn1 site mutations affected the positions of Zn2 and the bridging hydroxide, by 0.8 to 1.2 Å, with the largest changes of ~1.5 Å observed on Zn2 ligand C221. A native hydrogen bond between H118 and D236 was disrupted in the H116N and H116Q mutants, which led to increased flexibility of loop 10. Consequently, residue N233 was no longer maintained at an optimal position for substrate binding. H116 connected loop 7 across Zn1 to loop 10, thereby contributed to the overall integrity. This work revealed that the H116-Zn1 interaction plays a critical role in defining the substrate-binding site. From these results, it can be inferred that inhibition strategies targeting the zinc ions may be a new direction for drug development.
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Affiliation(s)
- Yik-Hong Fung
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Wai-Po Kong
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Alan Siu Lun Leung
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Ruolan Du
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Pu-Kin So
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Wing-Leung Wong
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Yun-Chung Leung
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Yu Wai Chen
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
| | - Kwok-Yin Wong
- The State Key Laboratory of Chemical Biology and Drug Discovery, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
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2
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Bahr G, González LJ, Vila AJ. Metallo-β-lactamases in the Age of Multidrug Resistance: From Structure and Mechanism to Evolution, Dissemination, and Inhibitor Design. Chem Rev 2021; 121:7957-8094. [PMID: 34129337 PMCID: PMC9062786 DOI: 10.1021/acs.chemrev.1c00138] [Citation(s) in RCA: 106] [Impact Index Per Article: 35.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Antimicrobial resistance is one of the major problems in current practical medicine. The spread of genes coding for resistance determinants among bacteria challenges the use of approved antibiotics, narrowing the options for treatment. Resistance to carbapenems, last resort antibiotics, is a major concern. Metallo-β-lactamases (MBLs) hydrolyze carbapenems, penicillins, and cephalosporins, becoming central to this problem. These enzymes diverge with respect to serine-β-lactamases by exhibiting a different fold, active site, and catalytic features. Elucidating their catalytic mechanism has been a big challenge in the field that has limited the development of useful inhibitors. This review covers exhaustively the details of the active-site chemistries, the diversity of MBL alleles, the catalytic mechanism against different substrates, and how this information has helped developing inhibitors. We also discuss here different aspects critical to understand the success of MBLs in conferring resistance: the molecular determinants of their dissemination, their cell physiology, from the biogenesis to the processing involved in the transit to the periplasm, and the uptake of the Zn(II) ions upon metal starvation conditions, such as those encountered during an infection. In this regard, the chemical, biochemical and microbiological aspects provide an integrative view of the current knowledge of MBLs.
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Affiliation(s)
- Guillermo Bahr
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
| | - Lisandro J. González
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
| | - Alejandro J. Vila
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Universidad Nacional de Rosario, Ocampo y Esmeralda S/N, 2000 Rosario, Argentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina
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3
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Fröhlich C, Sørum V, Huber S, Samuelsen Ø, Berglund F, Kristiansson E, Kotsakis SD, Marathe NP, Larsson DGJ, Leiros HKS. Structural and biochemical characterization of the environmental MBLs MYO-1, ECV-1 and SHD-1. J Antimicrob Chemother 2021; 75:2554-2563. [PMID: 32464640 PMCID: PMC7443720 DOI: 10.1093/jac/dkaa175] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 03/27/2020] [Accepted: 04/06/2020] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND MBLs form a large and heterogeneous group of bacterial enzymes conferring resistance to β-lactam antibiotics, including carbapenems. A large environmental reservoir of MBLs has been identified, which can act as a source for transfer into human pathogens. Therefore, structural investigation of environmental and clinically rare MBLs can give new insights into structure-activity relationships to explore the role of catalytic and second shell residues, which are under selective pressure. OBJECTIVES To investigate the structure and activity of the environmental subclass B1 MBLs MYO-1, SHD-1 and ECV-1. METHODS The respective genes of these MBLs were cloned into vectors and expressed in Escherichia coli. Purified enzymes were characterized with respect to their catalytic efficiency (kcat/Km). The enzymatic activities and MICs were determined for a panel of different β-lactams, including penicillins, cephalosporins and carbapenems. Thermostability was measured and structures were solved using X-ray crystallography (MYO-1 and ECV-1) or generated by homology modelling (SHD-1). RESULTS Expression of the environmental MBLs in E. coli resulted in the characteristic MBL profile, not affecting aztreonam susceptibility and decreasing susceptibility to carbapenems, cephalosporins and penicillins. The purified enzymes showed variable catalytic activity in the order of <5% to ∼70% compared with the clinically widespread NDM-1. The thermostability of ECV-1 and SHD-1 was up to 8°C higher than that of MYO-1 and NDM-1. Using solved structures and molecular modelling, we identified differences in their second shell composition, possibly responsible for their relatively low hydrolytic activity. CONCLUSIONS These results show the importance of environmental species acting as reservoirs for MBL-encoding genes.
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Affiliation(s)
- Christopher Fröhlich
- The Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, UiT The Arctic University of Norway, Tromsø, Norway
| | - Vidar Sørum
- Department of Pharmacy, UiT The Arctic University of Norway, Tromsø, Norway
| | - Sandra Huber
- Department of Laboratory Medicine, University Hospital of North Norway, Tromsø, Norway
| | - Ørjan Samuelsen
- Department of Pharmacy, UiT The Arctic University of Norway, Tromsø, Norway.,Norwegian National Advisory Unit on Detection of Antimicrobial Resistance, Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway
| | - Fanny Berglund
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.,Department of Infectious Diseases, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - Erik Kristiansson
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - Stathis D Kotsakis
- Department of Infectious Diseases, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - Nachiket P Marathe
- Department of Mathematical Sciences, Chalmers University of Technology, Gothenburg, Sweden.,Department of Infectious Diseases, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden.,Institute of Marine Research, Bergen, Norway
| | - D G Joakim Larsson
- Department of Infectious Diseases, Institute of Biomedicine, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.,Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden
| | - Hanna-Kirsti S Leiros
- The Norwegian Structural Biology Centre (NorStruct), Department of Chemistry, UiT The Arctic University of Norway, Tromsø, Norway
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4
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Levina EO, Khrenova MG. Metallo-β-Lactamases: Influence of the Active Site Structure on the Mechanisms of Antibiotic Resistance and Inhibition. BIOCHEMISTRY (MOSCOW) 2021; 86:S24-S37. [PMID: 33827398 DOI: 10.1134/s0006297921140030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The review focuses on bacterial metallo-β-lactamases (MβLs) responsible for the inactivation of β-lactams and associated antibiotic resistance. The diversity of the active site structure in the members of different MβL subclasses explains different mechanisms of antibiotic hydrolysis and should be taken into account when searching for potential MβL inhibitors. The review describes the features of the antibiotic inactivation mechanisms by various MβLs studied by X-ray crystallography, NMR, kinetic measurements, and molecular modeling. The mechanisms of enzyme inhibition for each MβL subclass are discussed.
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Affiliation(s)
- Elena O Levina
- Bach Institute of Biochemistry, Federal Research Centre "Fundamentals of Biotechnology", Russian Academy of Sciences, Moscow, 119071, Russia
| | - Maria G Khrenova
- Bach Institute of Biochemistry, Federal Research Centre "Fundamentals of Biotechnology", Russian Academy of Sciences, Moscow, 119071, Russia. .,Faculty of Chemistry, Lomonosov Moscow State University, Moscow, 119991, Russia
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5
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Mutational Effects on Carbapenem Hydrolysis of YEM-1, a New Subclass B2 Metallo-β-Lactamase from Yersinia mollaretii. Antimicrob Agents Chemother 2020; 64:AAC.00105-20. [PMID: 32540974 DOI: 10.1128/aac.00105-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 05/22/2020] [Indexed: 11/20/2022] Open
Abstract
Analysis of the genome sequence of Yersinia mollaretii ATCC 43969 identified the bla YEM gene, encoding YEM-1, a putative subclass B2 metallo-β-lactamase. The objectives of our work were to produce and purify YEM-1 and to complete its kinetic characterization. YEM-1 displayed the narrowest substrate range among known subclass B2 metallo-β-lactamases, since it can hydrolyze imipenem, but not other carbapenems, such as biapenem, meropenem, doripenem, and ertapenem, with high catalytic efficiency. A possible explanation of this activity profile is the presence of tyrosine at residue 67 (loop L1), threonine at residue 156 (loop L2), and serine at residue 236 (loop L3). We showed that replacement of Y67 broadened the activity profile of the enzyme for all carbapenems but still resulted in poor activity toward the other β-lactam classes.
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6
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Chen J, Wang J, Pang L, Wang W, Zhao J, Zhu W. Deciphering molecular mechanism behind conformational change of the São Paolo metallo-β-lactamase 1 by using enhanced sampling. J Biomol Struct Dyn 2019; 39:140-151. [DOI: 10.1080/07391102.2019.1707121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Jianzhong Chen
- School of Science, Shandong Jiaotong University, Jinan, China
| | - Jinan Wang
- Drug Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Laixue Pang
- School of Science, Shandong Jiaotong University, Jinan, China
| | - Wei Wang
- School of Science, Shandong Jiaotong University, Jinan, China
| | - Juan Zhao
- School of Science, Shandong Jiaotong University, Jinan, China
| | - Weiliang Zhu
- Drug Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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7
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Tripathi R, Noetzel J, Marx D. Exposing catalytic versatility of GTPases: taking reaction detours in mutants of hGBP1 enzyme without additional energetic cost. Phys Chem Chem Phys 2019; 21:859-867. [DOI: 10.1039/c8cp06343e] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Our study reveals that the replacement of catalytically competent residues by the inert amino acid alanine, S73A and E99A, in hGBP1 opens a plethora of molecularly different reaction pathways featuring very similar energy barriers as the wild type.
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Affiliation(s)
- Ravi Tripathi
- Lehrstuhl für Theoretische Chemie
- Ruhr-Universität Bochum
- 44780 Bochum
- Germany
| | - Jan Noetzel
- Lehrstuhl für Theoretische Chemie
- Ruhr-Universität Bochum
- 44780 Bochum
- Germany
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie
- Ruhr-Universität Bochum
- 44780 Bochum
- Germany
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8
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Mojica MF, Bonomo RA, Fast W. B1-Metallo-β-Lactamases: Where Do We Stand? Curr Drug Targets 2017; 17:1029-50. [PMID: 26424398 DOI: 10.2174/1389450116666151001105622] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 12/31/1969] [Accepted: 09/14/2015] [Indexed: 11/22/2022]
Abstract
Metallo-β-Lactamases (MBLs) are class Bβ-lactamases that hydrolyze almost all clinically-availableβ-lactam antibiotics. MBLs feature the distinctive αβ/βα sandwich fold of the metallo-hydrolase/oxidoreductase superfamily and possess a shallow active-site groove containing one or two divalent zinc ions, flanked by flexible loops. According to sequence identity and zinc ion dependence, MBLs are classified into three subclasses (B1, B2 and B3), of which the B1 subclass enzymes have emerged as the most clinically significant. Differences among the active site architectures, the nature of zinc ligands, and the catalytic mechanisms have limited the development of a common inhibitor. In this review, we will describe the molecular epidemiology and structural studies of the most prominent representatives of class B1 MBLs (NDM-1, IMP-1 and VIM-2) and describe the implications for inhibitor design to counter this growing clinical threat.
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Affiliation(s)
| | - Robert A Bonomo
- Medical Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, 10701 East Blvd., Cleveland, OH 44106, USA.
| | - Walter Fast
- Division of Medicinal Chemistry, College of Pharmacy, University of Texas, Austin TX, 78712, USA.
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9
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Sun Z, Mehta SC, Adamski CJ, Gibbs RA, Palzkill T. Deep Sequencing of Random Mutant Libraries Reveals the Active Site of the Narrow Specificity CphA Metallo-β-Lactamase is Fragile to Mutations. Sci Rep 2016; 6:33195. [PMID: 27616327 PMCID: PMC5018959 DOI: 10.1038/srep33195] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/23/2016] [Indexed: 11/17/2022] Open
Abstract
CphA is a Zn2+-dependent metallo-β-lactamase that efficiently hydrolyzes only carbapenem antibiotics. To understand the sequence requirements for CphA function, single codon random mutant libraries were constructed for residues in and near the active site and mutants were selected for E. coli growth on increasing concentrations of imipenem, a carbapenem antibiotic. At high concentrations of imipenem that select for phenotypically wild-type mutants, the active-site residues exhibit stringent sequence requirements in that nearly all residues in positions that contact zinc, the substrate, or the catalytic water do not tolerate amino acid substitutions. In addition, at high imipenem concentrations a number of residues that do not directly contact zinc or substrate are also essential and do not tolerate substitutions. Biochemical analysis confirmed that amino acid substitutions at essential positions decreased the stability or catalytic activity of the CphA enzyme. Therefore, the CphA active - site is fragile to substitutions, suggesting active-site residues are optimized for imipenem hydrolysis. These results also suggest that resistance to inhibitors targeted to the CphA active site would be slow to develop because of the strong sequence constraints on function.
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Affiliation(s)
- Zhizeng Sun
- Department of Pharmacology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Shrenik C Mehta
- Department of Pharmacology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Carolyn J Adamski
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
| | - Timothy Palzkill
- Department of Pharmacology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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10
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González MM, Vila AJ. An Elusive Task: A Clinically Useful Inhibitor of Metallo-β-Lactamases. TOPICS IN MEDICINAL CHEMISTRY 2016. [DOI: 10.1007/7355_2016_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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11
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Elucidating the Role of Residue 67 in IMP-Type Metallo-β-Lactamase Evolution. Antimicrob Agents Chemother 2015; 59:7299-307. [PMID: 26369960 DOI: 10.1128/aac.01651-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/06/2015] [Indexed: 02/07/2023] Open
Abstract
Antibiotic resistance in bacteria is ever changing and adapting, as once-novel β-lactam antibiotics are losing their efficacy, primarily due to the production of β-lactamases. Metallo-β-lactamases (MBLs) efficiently inactivate a broad range of β-lactam antibiotics, including carbapenems, and are often coexpressed with other antibacterial resistance factors. The rapid dissemination of MBLs and lack of novel antibacterials pose an imminent threat to global health. In an effort to better counter these resistance-conferring β-lactamases, an investigation of their natural evolution and resulting substrate specificity was employed. In this study, we elucidated the effects of different amino acid substitutions at position 67 in IMP-type MBLs on the ability to hydrolyze and confer resistance to a range of β-lactam antibiotics. Wild-type β-lactamases IMP-1 and IMP-10 and mutants IMP-1-V67A and IMP-1-V67I were characterized biophysically and biochemically, and MICs for Escherichia coli cells expressing these enzymes were determined. We found that all variants exhibited catalytic efficiencies (kcat/Km) equal to or higher than that of IMP-1 against all tested β-lactams except penicillins, against which IMP-1 and IMP-1-V67I showed the highest kcat/Km values. The substrate-specific effects of the different amino acid substitutions at position 67 are discussed in light of their side chain structures and possible interactions with the substrates. Docking calculations were employed to investigate interactions between different side chains and an inhibitor used as a β-lactam surrogate. The differences in binding affinities determined experimentally and computationally seem to be governed by hydrophobic interactions between residue 67 and the inhibitor and, by inference, the β-lactam substrates.
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12
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Meini MR, Llarrull LI, Vila AJ. Overcoming differences: The catalytic mechanism of metallo-β-lactamases. FEBS Lett 2015; 589:3419-32. [PMID: 26297824 DOI: 10.1016/j.febslet.2015.08.015] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 07/27/2015] [Accepted: 08/05/2015] [Indexed: 10/23/2022]
Abstract
Metallo-β-lactamases are the latest resistance mechanism of pathogenic and opportunistic bacteria against carbapenems, considered as last resort drugs. The worldwide spread of genes coding for these enzymes, together with the lack of a clinically useful inhibitor, have raised a sign of alarm. Inhibitor design has been mostly impeded by the structural diversity of these enzymes. Here we provide a critical review of mechanistic studies of the three known subclasses of metallo-β-lactamases, analyzed at the light of structural and mutagenesis investigations. We propose that these enzymes present a modular structure in their active sites that can be dissected into two halves: one providing the attacking nucleophile, and the second one stabilizing a negatively charged reaction intermediate. These are common mechanistic elements in all metallo-β-lactamases. Nucleophile activation does not necessarily requires a Zn(II) ion, but a Zn(II) center is essential for stabilization of the anionic intermediate. Design of a common inhibitor could be therefore approached based in these convergent mechanistic features despite the structural differences.
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Affiliation(s)
- María-Rocío Meini
- Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 200 Rosario, Argentina
| | - Leticia I Llarrull
- Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 200 Rosario, Argentina; Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 2000 Rosario, Argentina.
| | - Alejandro J Vila
- Área Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 200 Rosario, Argentina; Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR), Predio CONICET Rosario, 2000 Rosario, Argentina.
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13
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Brem J, Struwe WB, Rydzik AM, Tarhonskaya H, Pfeffer I, Flashman E, van Berkel SS, Spencer J, Claridge TDW, McDonough MA, Benesch JLP, Schofield CJ. Studying the active-site loop movement of the São Paolo metallo-β-lactamase-1†Electronic supplementary information (ESI) available: Procedures for protein expression and purification, 19F-labelling, crystallisation, data collection, and structure determination, table of crystallographic data, table of crystallographic parameters and refinement statistics, figures showing binding mode and distances, procedures for mass spectrometry measurements, differential scanning fluorimetry measurements, stopped-flow measurements and other kinetics measurements. See DOI: 10.1039/c4sc01752hClick here for additional data file. Chem Sci 2015; 6:956-963. [PMID: 25717359 PMCID: PMC4333608 DOI: 10.1039/c4sc01752h] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 10/24/2014] [Indexed: 11/21/2022] Open
Abstract
Metallo-β-lactamases (MBLs) catalyse the hydrolysis of almost all β-lactam antibiotics. We report biophysical and kinetic studies on the São Paulo MBL (SPM-1), which reveal its Zn(ii) ion usage and mechanism as characteristic of the clinically important di-Zn(ii) dependent B1 MBL subfamily. Biophysical analyses employing crystallography, dynamic 19F NMR and ion mobility mass spectrometry, however, reveal that SPM-1 possesses loop and mobile element regions characteristic of the B2 MBLs. These include a mobile α3 region which is important in catalysis and determining inhibitor selectivity. SPM-1 thus appears to be a hybrid B1/B2 MBL. The results have implications for MBL evolution and inhibitor design.
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Affiliation(s)
- Jürgen Brem
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Weston B Struwe
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford , OX1 3QZ , UK .
| | - Anna M Rydzik
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Hanna Tarhonskaya
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Inga Pfeffer
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Emily Flashman
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Sander S van Berkel
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - James Spencer
- School of Cellular and Molecular Medicine , University of Bristol , Medical Sciences Building , Bristol , BS8 1TD , UK
| | - Timothy D W Claridge
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Michael A McDonough
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
| | - Justin L P Benesch
- Department of Chemistry , Physical and Theoretical Chemistry Laboratory , University of Oxford , South Parks Road , Oxford , OX1 3QZ , UK .
| | - Christopher J Schofield
- Department of Chemistry , University of Oxford , 12 Mansfield Road , Oxford , OX1 3TA , UK .
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14
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Mitić N, Miraula M, Selleck C, Hadler KS, Uribe E, Pedroso MM, Schenk G. Catalytic mechanisms of metallohydrolases containing two metal ions. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2014; 97:49-81. [PMID: 25458355 DOI: 10.1016/bs.apcsb.2014.07.002] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
At least one-third of enzymes contain metal ions as cofactors necessary for a diverse range of catalytic activities. In the case of polymetallic enzymes (i.e., two or more metal ions involved in catalysis), the presence of two (or more) closely spaced metal ions gives an additional advantage in terms of (i) charge delocalisation, (ii) smaller activation barriers, (iii) the ability to bind larger substrates, (iv) enhanced electrostatic activation of substrates, and (v) decreased transition-state energies. Among this group of proteins, enzymes that catalyze the hydrolysis of ester and amide bonds form a very prominent family, the metallohydrolases. These enzymes are involved in a multitude of biological functions, and an increasing number of them gain attention for translational research in medicine and biotechnology. Their functional versatility and catalytic proficiency are largely due to the presence of metal ions in their active sites. In this chapter, we thus discuss and compare the reaction mechanisms of several closely related enzymes with a view to highlighting the functional diversity bestowed upon them by their metal ion cofactors.
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Affiliation(s)
- Nataša Mitić
- Department of Chemistry, National University of Ireland, Maynooth, Maynooth, Co. Kildare, Ireland.
| | - Manfredi Miraula
- Department of Chemistry, National University of Ireland, Maynooth, Maynooth, Co. Kildare, Ireland; School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Christopher Selleck
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Kieran S Hadler
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Elena Uribe
- Department of Biochemistry and Molecular Biology, University of Concepción, Concepción, Chile
| | - Marcelo M Pedroso
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Gerhard Schenk
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia.
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15
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Feng H, Ding J, Zhu D, Liu X, Xu X, Zhang Y, Zang S, Wang DC, Liu W. Structural and mechanistic insights into NDM-1 catalyzed hydrolysis of cephalosporins. J Am Chem Soc 2014; 136:14694-7. [PMID: 25268575 DOI: 10.1021/ja508388e] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cephalosporins constitute a large class of β-lactam antibiotics clinically used as antimicrobial drugs. New Dehli metallo-β-lactamase (NDM-1) poses a global threat to human health as it confers on bacterial pathogen resistance to almost all β-lactams, including penicillins, cephalosporins, and carbapenems. Here we report the first crystal structures of NDM-1 in complex with cefuroxime and cephalexin, as well as NMR spectra monitoring cefuroxime and cefixime hydrolysis catalyzed by NDM-1. Surprisingly, cephalosporoate intermediates were captured in both crystal structures determined at 1.3 and 2.0 Å. These results provide detailed information concerning the mechanism and pathways of cephalosporin hydrolysis. We also present the crystal structure and enzyme assays of a D124N mutant, which reveals that D124 most likely plays a more structural than catalytic role.
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Affiliation(s)
- Han Feng
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences , Beijing 100101, China
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16
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His224 alters the R2 drug binding site and Phe218 influences the catalytic efficiency of the metallo-β-lactamase VIM-7. Antimicrob Agents Chemother 2014; 58:4826-36. [PMID: 24913158 DOI: 10.1128/aac.02735-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Metallo-β-lactamases (MBLs) are the causative mechanism for resistance to β-lactams, including carbapenems, in many Gram-negative pathogenic bacteria. One important family of MBLs is the Verona integron-encoded MBLs (VIM). In this study, the importance of residues Asp120, Phe218, and His224 in the most divergent VIM variant, VIM-7, was investigated to better understand the roles of these residues in VIM enzymes through mutations, enzyme kinetics, crystal structures, thermostability, and docking experiments. The tVIM-7-D120A mutant with a tobacco etch virus (TEV) cleavage site was enzymatically inactive, and its structure showed the presence of only the Zn1 ion. The mutant was less thermostable, with a melting temperature (T(m)) of 48.5°C, compared to 55.3 °C for the wild-type tVIM-7. In the F218Y mutant, a hydrogen bonding cluster was established involving residues Asn70, Asp84, and Arg121. The tVIM-7-F218Y mutant had enhanced activity compared to wild-type tVIM-7, and a slightly higher Tm (57.1 °C) was observed, most likely due to the hydrogen bonding cluster. Furthermore, the introduction of two additional hydrogen bonds adjacent to the active site in the tVIM-7-H224Y mutant gave a higher thermostability (T(m), 62.9 °C) and increased enzymatic activity compared to those of the wild-type tVIM-7. Docking of ceftazidime in to the active site of tVIM-7, tVIM-7-H224Y, and VIM-7-F218Y revealed that the side-chain conformations of residue 224 and Arg228 in the L3 loop and Tyr67 in the L1 loop all influence possible substrate binding conformations. In conclusion, the residue composition of the L3 loop, as shown with the single H224Y mutation, is important for activity particularly toward the positively charged cephalosporins like cefepime and ceftazidime.
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17
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Kim Y, Cunningham MA, Mire J, Tesar C, Sacchettini J, Joachimiak A. NDM-1, the ultimate promiscuous enzyme: substrate recognition and catalytic mechanism. FASEB J 2013; 27:1917-27. [PMID: 23363572 DOI: 10.1096/fj.12-224014] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The specter of a return to an era in which infectious disease looms as a significant threat to human health is not just hyperbole; there are serious concerns about the widespread overuse and misuse of antibiotics contributing to increased antibiotic resistance in pathogens. The recent discovery of a new enzyme, first identified in Klebsiella pneumoniae from a patient from New Delhi and denoted as NDM-1, represents an example of extreme promiscuity: It hydrolyzes and inactivates nearly all known β-lactam-based antibiotics with startling efficiency. NDM-1 can utilize different metal cofactors and seems to exploit an alternative mechanism based on the reaction conditions. Here we report the results of a combined experimental and theoretical study that examines the substrate, metal binding, and catalytic mechanism of the enzyme. We utilize structures obtained through X-ray crystallography, biochemical assays, and numerical simulation to construct a model of the enzyme catalytic pathway. The NDM-1 enzyme interacts with the substrate solely through zinc, or other metals, bound in the active site, explaining the observed lack of specificity against a broad range of β-lactam antibiotic agents. The zinc ions also serve to activate a water molecule that hydrolyzes the β-lactam ring through a proton shuttle.
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Affiliation(s)
- Youngchang Kim
- Midwest Center for Structural Genomics and Structural Biology Center, Biosciences, Argonne National Laboratory, Argonne, IL 60439, USA
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18
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Abstract
β-Lactam antibiotics are the most commonly used antibacterial agents and growing resistance to these drugs is a concern. Metallo-β-lactamases are a diverse set of enzymes that catalyze the hydrolysis of a broad range of β-lactam drugs including carbapenems. This diversity is reflected in the observation that the enzyme mechanisms differ based on whether one or two zincs are bound in the active site that, in turn, is dependent on the subclass of β-lactamase. The dissemination of the genes encoding these enzymes among Gram-negative bacteria has made them an important cause of resistance. In addition, there are currently no clinically available inhibitors to block metallo-β-lactamase action. This review summarizes the numerous studies that have yielded insights into the structure, function, and mechanism of action of these enzymes.
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Affiliation(s)
- Timothy Palzkill
- Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030, USA.
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19
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Detection and characterization of VIM-31, a new variant of VIM-2 with Tyr224His and His252Arg mutations, in a clinical isolate of Enterobacter cloacae. Antimicrob Agents Chemother 2012; 56:3283-7. [PMID: 22391550 DOI: 10.1128/aac.06249-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the first description of the metallo-β-lactamase VIM-31, a new variant of VIM-2 with Tyr224His and His252Arg mutations, in Enterobacter cloacae 11236, which was isolated from blood specimens of a patient with colonic adenocarcinoma in Belgium. bla(VIM-31) was found on a class 1 integron located on a self-transferable but not typeable 42-kb plasmid. Compared to values published elsewhere for VIM-2, the purified VIM-31 enzyme showed weaker catalytic efficiency against all the tested beta-lactam agents (except for ertapenem), resulting from lower k(cat) (except for ertapenem) and higher K(m) values for VIM-31.
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20
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Papp-Wallace KM, Endimiani A, Taracila MA, Bonomo RA. Carbapenems: past, present, and future. Antimicrob Agents Chemother 2011; 55:4943-60. [PMID: 21859938 PMCID: PMC3195018 DOI: 10.1128/aac.00296-11] [Citation(s) in RCA: 877] [Impact Index Per Article: 67.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In this review, we summarize the current "state of the art" of carbapenem antibiotics and their role in our antimicrobial armamentarium. Among the β-lactams currently available, carbapenems are unique because they are relatively resistant to hydrolysis by most β-lactamases, in some cases act as "slow substrates" or inhibitors of β-lactamases, and still target penicillin binding proteins. This "value-added feature" of inhibiting β-lactamases serves as a major rationale for expansion of this class of β-lactams. We describe the initial discovery and development of the carbapenem family of β-lactams. Of the early carbapenems evaluated, thienamycin demonstrated the greatest antimicrobial activity and became the parent compound for all subsequent carbapenems. To date, more than 80 compounds with mostly improved antimicrobial properties, compared to those of thienamycin, are described in the literature. We also highlight important features of the carbapenems that are presently in clinical use: imipenem-cilastatin, meropenem, ertapenem, doripenem, panipenem-betamipron, and biapenem. In closing, we emphasize some major challenges and urge the medicinal chemist to continue development of these versatile and potent compounds, as they have served us well for more than 3 decades.
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Affiliation(s)
- Krisztina M. Papp-Wallace
- Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio 44106
- Departments of Medicine
| | - Andrea Endimiani
- Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio 44106
- Institute for Infectious Diseases, University of Bern 3010, Bern, Switzerland
- Departments of Medicine
| | | | - Robert A. Bonomo
- Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio 44106
- Departments of Medicine
- Pharmacology
- Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, Ohio 44106
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21
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The CphAII protein from Aquifex aeolicus exhibits a metal-dependent phosphodiesterase activity. Extremophiles 2011; 16:45-55. [PMID: 22009263 DOI: 10.1007/s00792-011-0404-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 10/05/2011] [Indexed: 10/16/2022]
Abstract
The CphAII protein from the hyperthermophile Aquifex aeolicus shows the five conserved motifs of the metallo-β-lactamase (MBL) superfamily and presents 28% identity with the Aeromonas hydrophila subclass B2 CphA MBL. The gene encoding CphAII was amplified by PCR from the A. aeolicus genomic DNA and overexpressed in Escherichia coli using a pLex-based expression system. The recombinant CphAII protein was purified by a combination of heating (to denature E. coli proteins) and two steps of immobilized metal affinity chromatography. The purified enzyme preparation did not exhibit a β-lactamase activity but showed a metal-dependent phosphodiesterase activity versus bis-p-nitrophenyl phosphate and thymidine 5'-monophosphate p-nitrophenyl ester, with an optimum at 85°C. The circular dichroism spectrum was in agreement with the percentage of secondary structures characteristic of the MBL αββα fold.
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22
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Biochemical and structural characterization of the subclass B1 metallo-β-lactamase VIM-4. Antimicrob Agents Chemother 2010; 55:1248-55. [PMID: 21149620 DOI: 10.1128/aac.01486-09] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The metallo-β-lactamase VIM-4, mainly found in Pseudomonas aeruginosa or Acinetobacter baumannii, was produced in Escherichia coli and characterized by biochemical and X-ray techniques. A detailed kinetic study performed in the presence of Zn²+ at concentrations ranging from 0.4 to 100 μM showed that VIM-4 exhibits a kinetic profile similar to the profiles of VIM-2 and VIM-1. However, VIM-4 is more active than VIM-1 against benzylpenicillin, cephalothin, nitrocefin, and imipenem and is less active than VIM-2 against ampicillin and meropenem. The crystal structure of the dizinc form of VIM-4 was solved at 1.9 Å. The sole difference between VIM-4 and VIM-1 is found at residue 228, which is Ser in VIM-1 and Arg in VIM-4. This substitution has a major impact on the VIM-4 catalytic efficiency compared to that of VIM-1. In contrast, the differences between VIM-2 and VIM-4 seem to be due to a different position of the flapping loop and two substitutions in loop 2. Study of the thermal stability and the activity of the holo- and apo-VIM-4 enzymes revealed that Zn²+ ions have a pronounced stabilizing effect on the enzyme and are necessary for preserving the structure.
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23
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Simona F, Magistrato A, Dal Peraro M, Cavalli A, Vila AJ, Carloni P. Common mechanistic features among metallo-beta-lactamases: a computational study of Aeromonas hydrophila CphA enzyme. J Biol Chem 2009; 284:28164-28171. [PMID: 19671702 DOI: 10.1074/jbc.m109.049502] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Metallo-beta-lactamases (MbetaLs) constitute an increasingly serious clinical threat by giving rise to beta-lactam antibiotic resistance. They accommodate in their catalytic pocket one or two zinc ions, which are responsible for the hydrolysis of beta-lactams. Recent x-ray studies on a member of the mono-zinc B2 MbetaLs, CphA from Aeromonas hydrophila, have paved the way to mechanistic studies of this important subclass, which is selective for carbapenems. Here we have used hybrid quantum mechanical/molecular mechanical methods to investigate the enzymatic hydrolysis by CphA of the antibiotic biapenem. Our calculations describe the entire reaction and point to a new mechanistic description, which is in agreement with the available experimental evidence. Within our proposal, the zinc ion properly orients the antibiotic while directly activating a second catalytic water molecule for the completion of the hydrolytic cycle. This mechanism provides an explanation for a variety of mutagenesis experiments and points to common functional facets across B2 and B1 MbetaLs.
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Affiliation(s)
- Fabio Simona
- Laboratory of Computational Chemistry and Biochemistry, Department für Chemie und Biochemie, Universität Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Alessandra Magistrato
- CNR-INFM-Democritos National Simulation Center, via Beirut 4, 34014 Grignano, Trieste, Italy; SISSA, Via Beirut 2-4, 34014 Grignano, Trieste, Italy
| | - Matteo Dal Peraro
- Laboratory for Biomolecular Modeling, Institute of Bioengineering, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, EPFL, CH-1015 Lausanne, Switzerland
| | - Andrea Cavalli
- Department of Pharmaceutical Sciences, University of Bologna, Via Belmeloro 6, I-40126 Bologna, Italy; Department of Drug Discovery and Development, Italian Institute of Technology, Via Morego 30, I-16163 Genova, Italy
| | - Alejandro J Vila
- Instituto de BiologiaMolecular y Celular de Rosario, Facultad de Bioquímicas y Farmaceuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina
| | - Paolo Carloni
- SISSA, Via Beirut 2-4, 34014 Grignano, Trieste, Italy.
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24
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The structure of the dizinc subclass B2 metallo-beta-lactamase CphA reveals that the second inhibitory zinc ion binds in the histidine site. Antimicrob Agents Chemother 2009; 53:4464-71. [PMID: 19651913 DOI: 10.1128/aac.00288-09] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacteria can defend themselves against beta-lactam antibiotics through the expression of class B beta-lactamases, which cleave the beta-lactam amide bond and render the molecule harmless. There are three subclasses of class B beta-lactamases (B1, B2, and B3), all of which require Zn2+ for activity and can bind either one or two zinc ions. Whereas the B1 and B3 metallo-beta-lactamases are most active as dizinc enzymes, subclass B2 enzymes, such as Aeromonas hydrophila CphA, are inhibited by the binding of a second zinc ion. We crystallized A. hydrophila CphA in order to determine the binding site of the inhibitory zinc ion. X-ray data from zinc-saturated crystals allowed us to solve the crystal structures of the dizinc forms of the wild-type enzyme and N220G mutant. The first zinc ion binds in the cysteine site, as previously determined for the monozinc form of the enzyme. The second zinc ion occupies a slightly modified histidine site, where the conserved His118 and His196 residues act as metal ligands. This atypical coordination sphere probably explains the rather high dissociation constant for the second zinc ion compared to those observed with enzymes of subclasses B1 and B3. Inhibition by the second zinc ion results from immobilization of the catalytically important His118 and His196 residues, as well as the folding of the Gly232-Asn233 loop into a position that covers the active site.
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25
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Balsalobre LC, Dropa M, Lincopan N, Mamizuka EM, Matté GR, Matté MH. Detection of metallo-beta-lactamases-encoding genes in environmental isolates of Aeromonas hydrophila and Aeromonas jandaei. Lett Appl Microbiol 2009; 49:142-5. [PMID: 19413767 DOI: 10.1111/j.1472-765x.2009.02625.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIMS To determine the prevalence and expression of metallo-beta-lactamases (MBL)-encoding genes in Aeromonas species recovered from natural water reservoirs in southeastern Brazil. METHODS AND RESULTS Eighty-seven Aeromonas isolates belonging to Aeromonas hydrophila (n = 41) and Aer. jandaei (n = 46) species were tested for MBL production by the combined disk test using imipenem and meropenem disks as substrates and EDTA or thioglycolic acid as inhibitors. The presence of MBL genes was investigated by PCR and sequencing using new consensus primer pairs designed in this study. The cphA gene was found in 97.6% and 100% of Aer. hydrophila and Aer. jandaei isolates, respectively, whereas the acquired MBL genes bla(IMP), bla(VIM) and bla(SPM-1) were not detected. On the other hand, production of MBL activity was detectable in 87.8% and 10.9% of the cphA-positive Aer. hydrophila and Aer. jandaei isolates respectively. CONCLUSIONS Our results indicate that cphA seems to be intrinsic in the environmental isolates of Aer. hydrophila and Aer. jandaei in southeastern Brazil, although, based on the combined disk test, not all of them are apparently able to express the enzymatic activity. SIGNIFICANCE AND IMPACT OF THE STUDY These data confirm the presence of MBL-producing Aeromonas species in natural water reservoirs. Risk of waterborne diseases owing to domestic and industrial uses of freshwater should be re-examined from the increase of bacterial resistance point of view.
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Affiliation(s)
- L C Balsalobre
- Public Health Laboratory, School of Public Health, University of São Paulo, São Paulo, Brazil.
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