1
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Jeong BG, Kim MY, Jeong CS, Do H, Hwang J, Lee JH, Cha SS. Characterization of the extended substrate spectrum of the class A β-lactamase CESS-1 from Stenotrophomonas sp. and structure-based investigation into its substrate preference. Int J Antimicrob Agents 2024; 63:107171. [PMID: 38588869 DOI: 10.1016/j.ijantimicag.2024.107171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 03/10/2024] [Accepted: 04/03/2024] [Indexed: 04/10/2024]
Abstract
OBJECTIVES Stenotrophomonas spp. intrinsically resistant to many β-lactam antibiotics are found throughout the environment. CESS-1 identified in Stenotrophomonas sp. KCTC 12332 is an uncharacterized class A β-lactamase. The goal of this study was to reveal biochemical and structural characteristics of CESS-1. METHODS The hydrolytic activities of CESS-1 towards penicillins (penicillin G and ampicillin), cephalosporins (cephalexin, cefaclor, and cefotaxime), and carbapenems (imipenem and meropenem) was spectrophotometrically monitored. Structural information on E166Q mutants of CESS-1 acylated by cefaclor, cephalexin, or ampicillin were determined by X-ray crystallography. RESULTS CESS-1 displayed hydrolytic activities toward penicillins and cephalosporins, with negligible activity toward carbapenems. Although cefaclor, cephalexin, and ampicillin have similar structures with identical R1 side chains, the catalytic parameters of CESS-1 toward them were distinct. The kcat values for cefaclor, cephalexin, and ampicillin were 1249.6 s-1, 204.3 s-1, and 69.8 s-1, respectively, with the accompanying KM values of 287.6 μM, 236.7 μM, and 28.8 μM, respectively. CONCLUSIONS CESS-1 was able to discriminate between cefaclor and cephalexin with a single structural difference at C3 position: -Cl (cefaclor) and -CH3 (cephalexin). Structural comparisons among three E166Q mutants of CESS-1 acylated by cefaclor, cephalexin, or ampicillin, revealed that cooperative positional changes in the R1 side chain of substrates and their interaction with the β5-β6 loop affect the distance between Asn170 and the deacylating water at the acyl-enzyme intermediate state. This is directly associated with the differential hydrolytic activities of CESS-1 toward the three structurally similar β-lactam antibiotics.
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Affiliation(s)
- Bo-Gyeong Jeong
- Department of Chemistry & Nanoscience, Ewha Womans University, Seoul, Republic of Korea
| | - Myeong-Yeon Kim
- Department of Chemistry & Nanoscience, Ewha Womans University, Seoul, Republic of Korea
| | - Chang-Sook Jeong
- Division of Life Sciences, Korea Polar Research Institute, Incheon, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon, Republic of Korea
| | - Hackwon Do
- Division of Life Sciences, Korea Polar Research Institute, Incheon, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon, Republic of Korea
| | - Jisub Hwang
- Division of Life Sciences, Korea Polar Research Institute, Incheon, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon, Republic of Korea
| | - Jun Hyuck Lee
- Division of Life Sciences, Korea Polar Research Institute, Incheon, Republic of Korea; Department of Polar Sciences, University of Science and Technology, Incheon, Republic of Korea.
| | - Sun-Shin Cha
- Department of Chemistry & Nanoscience, Ewha Womans University, Seoul, Republic of Korea.
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2
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Kawai A, Shropshire WC, Suzuki M, Borjan J, Aitken SL, Bachman WC, McElheny CL, Bhatti MM, Shields RK, Shelburne SA, Doi Y. Structural insights into the molecular mechanism of high-level ceftazidime-avibactam resistance conferred by CMY-185. mBio 2024; 15:e0287423. [PMID: 38179965 PMCID: PMC10865806 DOI: 10.1128/mbio.02874-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 11/27/2023] [Indexed: 01/06/2024] Open
Abstract
β-Lactamases can accumulate stepwise mutations that increase their resistance profiles to the latest β-lactam agents. CMY-185 is a CMY-2-like β-lactamase and was identified in an Escherichia coli clinical strain isolated from a patient who underwent treatment with ceftazidime-avibactam. CMY-185, possessing four amino acid substitutions of A114E, Q120K, V211S, and N346Y relative to CMY-2, confers high-level ceftazidime-avibactam resistance, and accumulation of the substitutions incrementally enhances the level of resistance to this agent. However, the functional role of each substitution and their interplay in enabling ceftazidime-avibactam resistance remains unknown. Through biochemical and structural analysis, we present the molecular basis for the enhanced ceftazidime hydrolysis and impaired avibactam inhibition conferred by CMY-185. The substituted Y346 residue is a major driver of the functional evolution as it rejects primary avibactam binding due to the steric hindrance and augments oxyimino-cephalosporin hydrolysis through a drastic structural change, rotating the side chain of Y346 and then disrupting the H-10 helix structure. The other substituted residues E114 and K120 incrementally contribute to rejection of avibactam inhibition, while S211 stimulates the turnover rate of the oxyimino-cephalosporin hydrolysis. These findings indicate that the N346Y substitution is capable of simultaneously expanding the spectrum of activity against some of the latest β-lactam agents with altered bulky side chains and rejecting the binding of β-lactamase inhibitors. However, substitution of additional residues may be required for CMY enzymes to achieve enhanced affinity or turnover rate of the β-lactam agents leading to clinically relevant levels of resistance.IMPORTANCECeftazidime-avibactam has a broad spectrum of activity against multidrug-resistant Gram-negative bacteria including carbapenem-resistant Enterobacterales including strains with or without production of serine carbapenemases. After its launch, emergence of ceftazidime-avibactam-resistant strains that produce mutated β-lactamases capable of efficiently hydrolyzing ceftazidime or impairing avibactam inhibition are increasingly reported. Furthermore, cross-resistance towards cefiderocol, the latest cephalosporin in clinical use, has been observed in some instances. Here, we clearly demonstrate the functional role of the substituted residues in CMY-185, a four amino-acid variant of CMY-2 identified in a patient treated with ceftazidime-avibactam, for high-level resistance to this agent and low-level resistance to cefiderocol. These findings provide structural insights into how β-lactamases may incrementally alter their structures to escape multiple advanced β-lactam agents.
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Affiliation(s)
- Akito Kawai
- Department of Microbiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
- Center for Infectious Disease Research, Fujita Health University, Toyoake, Aichi, Japan
| | - William C. Shropshire
- Department of Infectious Diseases, Infection Control, and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Masahiro Suzuki
- Department of Microbiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
- Center for Infectious Disease Research, Fujita Health University, Toyoake, Aichi, Japan
| | - Jovan Borjan
- Division of Pharmacy, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Samuel L. Aitken
- Division of Pharmacy, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - William C. Bachman
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Christi L. McElheny
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Micah M. Bhatti
- Division of Pathology/Lab Medicine, Department of Laboratory Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Ryan K. Shields
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Samuel A. Shelburne
- Department of Infectious Diseases, Infection Control, and Employee Health, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Yohei Doi
- Department of Microbiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
- Center for Infectious Disease Research, Fujita Health University, Toyoake, Aichi, Japan
- Division of Infectious Diseases, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Infectious Diseases, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
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3
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Sharkady SM, Bailey B, Thompson DK. Characterization of Two Novel AmpC Beta-Lactamases from the Emerging Opportunistic Pathogen, Cedecea neteri. Antibiotics (Basel) 2023; 12:antibiotics12020219. [PMID: 36830129 PMCID: PMC9952435 DOI: 10.3390/antibiotics12020219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/06/2023] [Accepted: 01/18/2023] [Indexed: 01/22/2023] Open
Abstract
The genus Cedecea (family Enterobacteriaceae) causes a wide spectrum of acute infections in immunocompromised hosts, from pneumonia and bacteremia to oral ulcers and dialysis-related peritonitis. While Cedecea infections are reported infrequently in the literature, documented clinical cases of this emerging opportunistic human pathogen have occurred worldwide. Cedecea neteri has clinical significance and exhibits antimicrobial drug resistance. However, little is known about the molecular basis underlying the resistance phenotypes in C. neteri. We previously hypothesized that the open-reading frame cnt10470 in the C. neteri SSMD04 genome encodes a chromosomal Ambler class C (AmpC) β-lactamase based on sequence homology. In this study, recombinant polyhistidine-tagged proteins were created by cloning the putative ampC genes from SSMD04 and C. neteri ATCC 33855 (a clinical isolate) into the pET-6xHN expression vector, overexpressing the proteins, and then purifying the recombinant AmpCs (rAmpCs) using immobilized metal affinity chromatography (Ni-NTA). The in vitro enzymatic analysis of the purified rAmpCs was performed to determine the Km and kcat for various β-lactam substrates. The rAmpCs are functional class C β-lactamases when assayed using the chromogenic β-lactamase substrate, nitrocefin. The presence of functional AmpCs in both C. neteri strains underscores the necessity of performing antibiotic susceptibility testing in the management of C. neteri infections.
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4
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Raja Reddy K, Totrov M, Lomovskaya O, Griffith DC, Tarazi Z, Clifton MC, Hecker SJ. Broad-spectrum cyclic boronate β-lactamase inhibitors featuring an intramolecular prodrug for oral bioavailability. Bioorg Med Chem 2022; 62:116722. [PMID: 35358864 DOI: 10.1016/j.bmc.2022.116722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 03/17/2022] [Accepted: 03/19/2022] [Indexed: 11/29/2022]
Abstract
Early efforts to broaden the spectrum and potency of cyclic boronic acid β-lactamase inhibitor vaborbactam included a series of 7-membered ring boronates. Exploration of stereoisomers and incorporation of heteroatoms allowed identification of the all-carbon cyclic boronate with substituents trans as the preferred core structure, showing inhibition of Class A and C enzymes. Crystal structures of one analog bound to important β-lactamase enzymes were obtained. When isolated under acidic conditions, these compounds spontaneously formed a neutral cyclic anhydride (intramolecular prodrug) which was shown to have much-improved oral bioavailability (52-69%) compared to the ring-opened carboxylate salt (9%).
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Affiliation(s)
- K Raja Reddy
- Qpex Biopharma, Inc, 6275 Nancy Ridge Dr., Suite 100, San Diego, CA 92121, United States
| | - Maxim Totrov
- Molsoft L.L.C, 11199 Sorrento Valley Road, San Diego, CA 92121, United States
| | - Olga Lomovskaya
- Qpex Biopharma, Inc, 6275 Nancy Ridge Dr., Suite 100, San Diego, CA 92121, United States
| | - David C Griffith
- Qpex Biopharma, Inc, 6275 Nancy Ridge Dr., Suite 100, San Diego, CA 92121, United States
| | - Ziad Tarazi
- Qpex Biopharma, Inc, 6275 Nancy Ridge Dr., Suite 100, San Diego, CA 92121, United States
| | - Matthew C Clifton
- Beryllium Discovery, 3 Preston Court, Bedford, MA 01730, United States
| | - Scott J Hecker
- Qpex Biopharma, Inc, 6275 Nancy Ridge Dr., Suite 100, San Diego, CA 92121, United States.
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5
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Abstract
Class C β-lactamases or cephalosporinases can be classified into two functional groups (1, 1e) with considerable molecular variability (≤20% sequence identity). These enzymes are mostly encoded by chromosomal and inducible genes and are widespread among bacteria, including Proteobacteria in particular. Molecular identification is based principally on three catalytic motifs (64SXSK, 150YXN, 315KTG), but more than 70 conserved amino-acid residues (≥90%) have been identified, many close to these catalytic motifs. Nevertheless, the identification of a tiny, phylogenetically distant cluster (including enzymes from the genera Legionella, Bradyrhizobium, and Parachlamydia) has raised questions about the possible existence of a C2 subclass of β-lactamases, previously identified as serine hydrolases. In a context of the clinical emergence of extended-spectrum AmpC β-lactamases (ESACs), the genetic modifications observed in vivo and in vitro (point mutations, insertions, or deletions) during the evolution of these enzymes have mostly involved the Ω- and H-10/R2-loops, which vary considerably between genera, and, in some cases, the conserved triplet 150YXN. Furthermore, the conserved deletion of several amino-acid residues in opportunistic pathogenic species of Acinetobacter, such as A. baumannii, A. calcoaceticus, A. pittii and A. nosocomialis (deletion of residues 304-306), and in Hafnia alvei and H. paralvei (deletion of residues 289-290), provides support for the notion of natural ESACs. The emergence of higher levels of resistance to β-lactams, including carbapenems, and to inhibitors such as avibactam is a reality, as the enzymes responsible are subject to complex regulation encompassing several other genes (ampR, ampD, ampG, etc.). Combinations of resistance mechanisms may therefore be at work, including overproduction or change in permeability, with the loss of porins and/or activation of efflux systems.
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6
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Crystal structure of AmpC BER and molecular docking lead to the discovery of broad inhibition activities of halisulfates against β-lactamases. Comput Struct Biotechnol J 2020; 19:145-152. [PMID: 33425247 PMCID: PMC7773887 DOI: 10.1016/j.csbj.2020.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/08/2020] [Accepted: 12/13/2020] [Indexed: 11/23/2022] Open
Abstract
AmpC BER is an extended-spectrum (ES) class C β-lactamase with a two-amino-acid insertion in the H10 helix region located at the boundary of the active site compared with its narrow spectrum progenitor. The crystal structure of the wild-type AmpC BER revealed that the insertion widens the active site by restructuring the flexible H10 helix region, which is the structural basis for its ES activity. Besides, two sulfates originated from the crystallization solution were observed in the active site. The presence of sulfate-binding subsites, together with the recognition of ring-structured chemical scaffolds by AmpC BER, led us to perform in silico molecular docking experiments with halisulfates, natural products isolated from marine sponge. Inspired by the snug fit of halisulfates within the active site, we demonstrated that halisulfate 3 and 5 significantly inhibit ES class C β-lactamases. Especially, halisulfate 5 is comparable to avibactam in terms of inhibition efficiency; it inhibits the nitrocefin-hydrolyzing activity of AmpC BER with a Ki value of 5.87 μM in a competitive manner. Furthermore, halisulfate 5 displayed moderate and weak inhibition activities against class A and class B/D enzymes, respectively. The treatment of β-lactamase inhibitors (BLIs) in combination with β-lactam antibiotics is a working strategy to cope with infections by pathogens producing ES β-lactamases. Considering the emergence and dissemination of enzymes insensitive to clinically-used BLIs, the broad inhibition spectrum and structural difference of halisulfates would be used to develop novel BLIs that can escape the bacterial resistance mechanism mediated by β-lactamases.
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7
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van den Akker F, Bonomo RA. Exploring Additional Dimensions of Complexity in Inhibitor Design for Serine β-Lactamases: Mechanistic and Intra- and Inter-molecular Chemistry Approaches. Front Microbiol 2018; 9:622. [PMID: 29675000 PMCID: PMC5895744 DOI: 10.3389/fmicb.2018.00622] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Accepted: 03/19/2018] [Indexed: 01/14/2023] Open
Abstract
As a bacterial resistance strategy, serine β-lactamases have evolved from cell wall synthesizing enzymes known as penicillin-binding proteins (PBP), by not only covalently binding β-lactam antibiotics but, also acquiring mechanisms of deacylating these antibiotics. This critical deacylation step leads to release of hydrolyzed and inactivated β-lactams, thereby providing resistance for the bacteria against these antibiotics targeting the cell wall. To combat β-lactamase-mediated antibiotic resistance, numerous β-lactamase inhibitors were developed that utilize various strategies to inactivate the β-lactamase. Most of these compounds are “mechanism-based” inhibitors that in some manner mimic the β-lactam substrate, having a carbonyl moiety and a negatively charged carboxyl or sulfate group. These compounds form a covalent adduct with the catalytic serine via an initial acylation step. To increase the life-time of the inhibitory covalent adduct intermediates, a remarkable array of different strategies was employed to improve inhibition potency. Such approaches include post-acylation intra- and intermolecular chemical rearrangements as well as affecting the deacylation water. These approaches transform the inhibitor design process from a 3-dimensional problem (i.e., XYZ coordinates) to one with additional dimensions of complexity as the reaction coordinate and time spent at each chemical state need to be taken into consideration. This review highlights the mechanistic intricacies of the design efforts of the β-lactamase inhibitors which so far have resulted in the development of “two generations” and 5 clinically available inhibitors.
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Affiliation(s)
- Focco van den Akker
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States
| | - Robert A Bonomo
- Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH, United States.,Medicine, Pharmacology, Molecular Biology and Microbiology, Proteomics and Bioinformatics, Case Western Reserve University School of Medicine, Cleveland, OH, United States.,Medical Service and Geriatric Research, Education, and Clinical Centers (GRECC), Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH, United States.,Case Western Reserve University-VA Medical Center for Antimicrobial Resistance and Epidemiology (Case VA CARES), Cleveland, OH, United States
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8
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Genovese F, Lazzari S, Venturi E, Costantino L, Blazquez J, Ibacache-Quiroga C, Costi MP, Tondi D. Design, synthesis and biological evaluation of non-covalent AmpC β-lactamases inhibitors. Med Chem Res 2017. [DOI: 10.1007/s00044-017-1809-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Negoro S, Kawashima Y, Shibata N, Kobayashi T, Baba T, Lee YH, Kamiya K, Shigeta Y, Nagai K, Takehara I, Kato DI, Takeo M, Higuchi Y. Mutations affecting the internal equilibrium of the reaction catalyzed by 6-aminohexanoate-dimer hydrolase. FEBS Lett 2016; 590:3133-43. [DOI: 10.1002/1873-3468.12354] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 08/03/2016] [Accepted: 08/04/2016] [Indexed: 12/14/2022]
Affiliation(s)
- Seiji Negoro
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Yasuyuki Kawashima
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Naoki Shibata
- Department of Life Science; Graduate School of Life Science; University of Hyogo; Himeji Hyogo Japan
| | - Tatsuya Kobayashi
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Takeshi Baba
- Department of Material Engineering Science; Graduate School of Engineering Science; Osaka University; Suita Japan
| | - Young-Ho Lee
- Institute for Protein Research; Osaka University; Suita Japan
| | - Katsumasa Kamiya
- Center for Basic Education and Integrated Learning; Kanagawa Institute of Technology; Atsugi Kanagawa Japan
| | - Yasuteru Shigeta
- Center for Computational Sciences; University of Tsukuba; Ibaraki Japan
| | - Keisuke Nagai
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Ikki Takehara
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Dai-ichiro Kato
- Graduate School of Science and Engineering; Kagoshima University; Japan
| | - Masahiro Takeo
- Department of Applied Chemistry; Graduate School of Engineering; University of Hyogo; Himeji Hyogo Japan
| | - Yoshiki Higuchi
- Department of Life Science; Graduate School of Life Science; University of Hyogo; Himeji Hyogo Japan
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10
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Crystal structure of EstSRT1, a family VIII carboxylesterase displaying hydrolytic activity toward oxyimino cephalosporins. Biochem Biophys Res Commun 2016; 478:818-24. [DOI: 10.1016/j.bbrc.2016.08.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2016] [Accepted: 08/04/2016] [Indexed: 11/20/2022]
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11
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Tripathi R, Nair NN. Deacylation Mechanism and Kinetics of Acyl-Enzyme Complex of Class C β-Lactamase and Cephalothin. J Phys Chem B 2016; 120:2681-90. [PMID: 26918257 DOI: 10.1021/acs.jpcb.5b11623] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Understanding the molecular details of antibiotic resistance by the bacterial enzymes β-lactamases is vital for the development of novel antibiotics and inhibitors. In this spirit, the detailed mechanism of deacylation of the acyl-enzyme complex formed by cephalothin and class C β-lactamase is investigated here using hybrid quantum-mechanical/molecular-mechanical molecular dynamics methods. The roles of various active-site residues and substrate in the deacylation reaction are elucidated. We identify the base that activates the hydrolyzing water molecule and the residue that protonates the catalytic serine (Ser64). Conformational changes in the active sites and proton transfers that potentiate the efficiency of the deacylation reaction are presented. We have also characterized the oxyanion holes and other H-bonding interactions that stabilize the reaction intermediates. Together with the kinetic and mechanistic details of the acylation reaction, we analyze the complete mechanism and the overall kinetics of the drug hydrolysis. Finally, the apparent rate-determining step in the drug hydrolysis is scrutinized.
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Affiliation(s)
- Ravi Tripathi
- Department of Chemistry, Indian Institute of Technology Kanpur , Kanpur 208016, India
| | - Nisanth N Nair
- Department of Chemistry, Indian Institute of Technology Kanpur , Kanpur 208016, India
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12
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Tilvawala R, Cammarata M, Adediran SA, Brodbelt JS, Pratt RF. A New Covalent Inhibitor of Class C β-Lactamases Reveals Extended Active Site Specificity. Biochemistry 2015; 54:7375-84. [DOI: 10.1021/acs.biochem.5b01149] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Ronak Tilvawala
- Department
of Chemistry, Wesleyan University, Middletown, Connecticut 06459, United States
| | - Michael Cammarata
- Department
of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - S. A. Adediran
- Department
of Chemistry, Wesleyan University, Middletown, Connecticut 06459, United States
| | - Jennifer S. Brodbelt
- Department
of Chemistry, University of Texas at Austin, Austin, Texas 78712-1224, United States
| | - R. F. Pratt
- Department
of Chemistry, Wesleyan University, Middletown, Connecticut 06459, United States
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13
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Brown JR, Livesay DR. Flexibility Correlation between Active Site Regions Is Conserved across Four AmpC β-Lactamase Enzymes. PLoS One 2015; 10:e0125832. [PMID: 26018804 PMCID: PMC4446314 DOI: 10.1371/journal.pone.0125832] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 03/26/2015] [Indexed: 11/24/2022] Open
Abstract
β-lactamases are bacterial enzymes that confer resistance to β-lactam antibiotics, such as penicillins and cephalosporins. There are four classes of β-lactamase enzymes, each with characteristic sequence and structure properties. Enzymes from class A are the most common and have been well characterized across the family; however, less is known about how physicochemical properties vary across the C and D families. In this report, we compare the dynamical properties of four AmpC (class C) β-lactamases using our distance constraint model (DCM). The DCM reliably predicts thermodynamic and mechanical properties in an integrated way. As a consequence, quantitative stability/flexibility relationships (QSFR) can be determined and compared across the whole family. The DCM calculates a large number of QSFR metrics. Perhaps the most useful is the flexibility index (FI), which quantifies flexibility along the enzyme backbone. As typically observed in other systems, FI is well conserved across the four AmpC enzymes. Cooperativity correlation (CC), which quantifies intramolecular couplings within structure, is rarely conserved across protein families; however, it is in AmpC. In particular, the bulk of each structure is composed of a large rigid cluster, punctuated by three flexibly correlated regions located at the active site. These regions include several catalytic residues and the Ω-loop. This evolutionary conservation combined with active their site location strongly suggests that these coupled dynamical modes are important for proper functioning of the enzyme.
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Affiliation(s)
- Jenna R. Brown
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, 28262, United States of America
| | - Dennis R. Livesay
- Department of Bioinformatics and Genomics, University of North Carolina at Charlotte, Charlotte, NC, 28262, United States of America
- * E-mail:
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14
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Hecker SJ, Reddy KR, Totrov M, Hirst GC, Lomovskaya O, Griffith DC, King P, Tsivkovski R, Sun D, Sabet M, Tarazi Z, Clifton MC, Atkins K, Raymond A, Potts KT, Abendroth J, Boyer SH, Loutit JS, Morgan EE, Durso S, Dudley MN. Discovery of a Cyclic Boronic Acid β-Lactamase Inhibitor (RPX7009) with Utility vs Class A Serine Carbapenemases. J Med Chem 2015; 58:3682-92. [PMID: 25782055 DOI: 10.1021/acs.jmedchem.5b00127] [Citation(s) in RCA: 298] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The increasing dissemination of carbapenemases in Gram-negative bacteria has threatened the clinical usefulness of the β-lactam class of antimicrobials. A program was initiated to discover a new series of serine β-lactamase inhibitors containing a boronic acid pharmacophore, with the goal of finding a potent inhibitor of serine carbapenemase enzymes that are currently compromising the utility of the carbapenem class of antibacterials. Potential lead structures were screened in silico by modeling into the active sites of key serine β-lactamases. Promising candidate molecules were synthesized and evaluated in biochemical and whole-cell assays. Inhibitors were identified with potent inhibition of serine carbapenemases, particularly the Klebsiella pneumoniae carbapenemase (KPC), with no inhibition of mammalian serine proteases. Studies in vitro and in vivo show that RPX7009 (9f) is a broad-spectrum inhibitor, notably restoring the activity of carbapenems against KPC-producing strains. Combined with a carbapenem, 9f is a promising product for the treatment of multidrug resistant Gram-negative bacteria.
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Affiliation(s)
- Scott J Hecker
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - K Raja Reddy
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Maxim Totrov
- ‡Molsoft L.L.C., 11199 Sorrento Valley Road, San Diego, California 92121, United States
| | - Gavin C Hirst
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Olga Lomovskaya
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - David C Griffith
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Paula King
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Ruslan Tsivkovski
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Dongxu Sun
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Mojgan Sabet
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Ziad Tarazi
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Matthew C Clifton
- §Beryllium, 3 Preston Court, Bedford, Massachusetts 01730, United States
| | - Kateri Atkins
- §Beryllium, 3 Preston Court, Bedford, Massachusetts 01730, United States
| | - Amy Raymond
- §Beryllium, 3 Preston Court, Bedford, Massachusetts 01730, United States
| | - Kristy T Potts
- §Beryllium, 3 Preston Court, Bedford, Massachusetts 01730, United States
| | - Jan Abendroth
- §Beryllium, 3 Preston Court, Bedford, Massachusetts 01730, United States
| | - Serge H Boyer
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Jeffrey S Loutit
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Elizabeth E Morgan
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Stephanie Durso
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
| | - Michael N Dudley
- †Rempex Pharmaceuticals, Inc., A Subsidiary of The Medicines Company, 3033 Science Park Rd., Suite 200, San Diego, California 92121, United States
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15
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Barelier S, Eidam O, Fish I, Hollander J, Figaroa F, Nachane R, Irwin JJ, Shoichet BK, Siegal G. Increasing chemical space coverage by combining empirical and computational fragment screens. ACS Chem Biol 2014; 9:1528-35. [PMID: 24807704 PMCID: PMC4215856 DOI: 10.1021/cb5001636] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Most libraries for fragment-based drug discovery are restricted to 1,000-10,000 compounds, but over 500,000 fragments are commercially available and potentially accessible by virtual screening. Whether this larger set would increase chemotype coverage, and whether a computational screen can pragmatically prioritize them, is debated. To investigate this question, a 1281-fragment library was screened by nuclear magnetic resonance (NMR) against AmpC β-lactamase, and hits were confirmed by surface plasmon resonance (SPR). Nine hits with novel chemotypes were confirmed biochemically with KI values from 0.2 to low mM. We also computationally docked 290,000 purchasable fragments with chemotypes unrepresented in the empirical library, finding 10 that had KI values from 0.03 to low mM. Though less novel than those discovered by NMR, the docking-derived fragments filled chemotype holes from the empirical library. Crystal structures of nine of the fragments in complex with AmpC β-lactamase revealed new binding sites and explained the relatively high affinity of the docking-derived fragments. The existence of chemotype holes is likely a general feature of fragment libraries, as calculation suggests that to represent the fragment substructures of even known biogenic molecules would demand a library of minimally over 32,000 fragments. Combining computational and empirical fragment screens enables the discovery of unexpected chemotypes, here by the NMR screen, while capturing chemotypes missing from the empirical library and tailored to the target, with little extra cost in resources.
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Affiliation(s)
- Sarah Barelier
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th St., Byers Hall, San Francisco, California 94158, United States
| | - Oliv Eidam
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th St., Byers Hall, San Francisco, California 94158, United States
| | - Inbar Fish
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th St., Byers Hall, San Francisco, California 94158, United States
- Department
of Biochemistry and Molecular Biology, George S. Wise Faculty of Life
SciencesTel-Aviv University, Ramat Aviv, Israel
| | | | | | - Ruta Nachane
- ZoBio, Eisteinweg 55, 2300-RA Leiden, The Netherlands
| | - John J. Irwin
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th St., Byers Hall, San Francisco, California 94158, United States
- Leslie
Dan Faculty of Pharmacy, University of Toronto, Donnelly Centre Suite 604, 160 College
Street, Toronto, Ontario, Canada M5S 3E1
| | - Brian K. Shoichet
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, 1700 4th St., Byers Hall, San Francisco, California 94158, United States
- Leslie
Dan Faculty of Pharmacy, University of Toronto, Donnelly Centre Suite 604, 160 College
Street, Toronto, Ontario, Canada M5S 3E1
| | - Gregg Siegal
- ZoBio, Eisteinweg 55, 2300-RA Leiden, The Netherlands
- Leiden University, Eisteinweg 55, 2300-RA Leiden, The Netherlands
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16
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Avibactam and class C β-lactamases: mechanism of inhibition, conservation of the binding pocket, and implications for resistance. Antimicrob Agents Chemother 2014; 58:5704-13. [PMID: 25022578 DOI: 10.1128/aac.03057-14] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Avibactam is a novel non-β-lactam β-lactamase inhibitor that inhibits a wide range of β-lactamases. These include class A, class C, and some class D enzymes, which erode the activity of β-lactam drugs in multidrug-resistant pathogens like Pseudomonas aeruginosa and Enterobacteriaceae spp. Avibactam is currently in clinical development in combination with the β-lactam antibiotics ceftazidime, ceftaroline fosamil, and aztreonam. Avibactam has the potential to be the first β-lactamase inhibitor that might provide activity against class C-mediated resistance, which represents a growing concern in both hospital- and community-acquired infections. Avibactam has an unusual mechanism of action: it is a covalent inhibitor that acts via ring opening, but in contrast to other currently used β-lactamase inhibitors, this reaction is reversible. Here, we present a high-resolution structure of avibactam bound to a class C β-lactamase, AmpC, from P. aeruginosa that provided insight into the mechanism of both acylation and recyclization in this enzyme class and highlighted the differences observed between class A and class C inhibition. Furthermore, variants resistant to avibactam that identified the residues important for inhibition were isolated. Finally, the structural information was used to predict effective inhibition by sequence analysis and functional studies of class C β-lactamases from a large and diverse set of contemporary clinical isolates (P. aeruginosa and several Enterobacteriaceae spp.) obtained from recent infections to understand any preexisting variability in the binding pocket that might affect inhibition by avibactam.
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17
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Barelier S, Cummings J, Rauwerdink AM, Hitchcock DS, Farelli JD, Almo SC, Raushel FM, Allen KN, Shoichet BK. Substrate deconstruction and the nonadditivity of enzyme recognition. J Am Chem Soc 2014; 136:7374-82. [PMID: 24791931 PMCID: PMC4046767 DOI: 10.1021/ja501354q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Indexed: 12/15/2022]
Abstract
Predicting substrates for enzymes of unknown function is a major postgenomic challenge. Substrate discovery, like inhibitor discovery, is constrained by our ability to explore chemotypes; it would be expanded by orders of magnitude if reactive sites could be probed with fragments rather than fully elaborated substrates, as is done for inhibitor discovery. To explore the feasibility of this approach, substrates of six enzymes from three different superfamilies were deconstructed into 41 overlapping fragments that were tested for activity or binding. Surprisingly, even those fragments containing the key reactive group had little activity, and most fragments did not bind measurably, until they captured most of the substrate features. Removing a single atom from a recognized substrate could often reduce catalytic recognition by 6 log-orders. To explore recognition at atomic resolution, the structures of three fragment complexes of the β-lactamase substrate cephalothin were determined by X-ray crystallography. Substrate discovery may be difficult to reduce to the fragment level, with implications for function discovery and for the tolerance of enzymes to metabolite promiscuity. Pragmatically, this study supports the development of libraries of fully elaborated metabolites as probes for enzyme function, which currently do not exist.
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Affiliation(s)
- Sarah Barelier
- Department
of Pharmaceutical Chemistry, University
of California - San Francisco, 1700 Fourth Street, Byers Hall, San Francisco, California 94158, United States
| | - Jennifer
A. Cummings
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Alissa M. Rauwerdink
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Daniel S. Hitchcock
- Department
of Biochemistry and Biophysics, Texas A&M
University, College Station, Texas, United States
| | - Jeremiah D. Farelli
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215-2521, United States
| | - Steven C. Almo
- Department
of Biochemistry, Albert Einstein College
of Medicine, New York, New York 10461, United
States
| | - Frank M. Raushel
- Department
of Chemistry, Texas A&M University, College Station, Texas 77843, United States
- Department
of Biochemistry and Biophysics, Texas A&M
University, College Station, Texas, United States
| | - Karen N. Allen
- Department
of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215-2521, United States
| | - Brian K. Shoichet
- Department
of Pharmaceutical Chemistry, University
of California - San Francisco, 1700 Fourth Street, Byers Hall, San Francisco, California 94158, United States
- Faculty of
Pharmacy, University of Toronto, Donnelly Centre Suite 604, 160 College
Street, Toronto, Ontario, Canada, M5S 3E1
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18
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Crystal structure of Mox-1, a unique plasmid-mediated class C β-lactamase with hydrolytic activity towards moxalactam. Antimicrob Agents Chemother 2014; 58:3914-20. [PMID: 24777102 DOI: 10.1128/aac.02363-13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Mox-1 is a unique plasmid-mediated class C β-lactamase that hydrolyzes penicillins, cephalothin, and the expanded-spectrum cephalosporins cefepime and moxalactam. In order to understand the unique substrate profile of this enzyme, we determined the X-ray crystallographic structure of Mox-1 β-lactamase at a 1.5-Å resolution. The overall structure of Mox-1 β-lactamase resembles that of other AmpC enzymes, with some notable exceptions. First, comparison with other enzymes whose structures have been solved reveals significant differences in the composition of amino acids that make up the hydrogen-bonding network and the position of structural elements in the substrate-binding cavity. Second, the main-chain electron density is not observed in two regions, one containing amino acid residues 214 to 216 positioned in the Ω loop and the other in the N terminus of the B3 β-strand corresponding to amino acid residues 303 to 306. The last two observations suggest that there is significant structural flexibility of these regions, a property which may impact the recognition and binding of substrates in Mox-1. These important differences allow us to propose that the binding of moxalactam in Mox-1 is facilitated by the avoidance of steric clashes, indicating that a substrate-induced conformational change underlies the basis of the hydrolytic profile of Mox-1 β-lactamase.
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19
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Bhattacharya M, Toth M, Antunes NT, Smith CA, Vakulenko SB. Structure of the extended-spectrum class C β-lactamase ADC-1 from Acinetobacter baumannii. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:760-71. [PMID: 24598745 PMCID: PMC3949520 DOI: 10.1107/s1399004713033014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 12/05/2013] [Indexed: 11/10/2022]
Abstract
ADC-type class C β-lactamases comprise a large group of enzymes that are encoded by genes located on the chromosome of Acinetobacter baumannii, a causative agent of serious bacterial infections. Overexpression of these enzymes renders A. baumannii resistant to various β-lactam antibiotics and thus severely compromises the ability to treat infections caused by this deadly pathogen. Here, the high-resolution crystal structure of ADC-1, the first member of this clinically important family of antibiotic-resistant enzymes, is reported. Unlike the narrow-spectrum class C β-lactamases, ADC-1 is capable of producing resistance to the expanded-spectrum cephalosporins, rendering them inactive against A. baumannii. The extension of the substrate profile of the enzyme is likely to be the result of structural differences in the R2-loop, primarily the deletion of three residues and subsequent rearrangement of the A10a and A10b helices. These structural rearrangements result in the enlargement of the R2 pocket of ADC-1, allowing it to accommodate the bulky R2 substituents of the third-generation cephalosporins, thus enhancing the catalytic efficiency of the enzyme against these clinically important antibiotics.
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Affiliation(s)
- Monolekha Bhattacharya
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Marta Toth
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Nuno Tiago Antunes
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
| | - Clyde A. Smith
- Stanford Synchrotron Radiation Lightsource, Stanford University, Menlo Park, California USA
| | - Sergei B. Vakulenko
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana, USA
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20
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Cha SS, An YJ, Jeong CS, Kim MK, Jeon JH, Lee CM, Lee HS, Kang SG, Lee JH. Structural basis for the β-lactamase activity of EstU1, a family VIII carboxylesterase. Proteins 2013; 81:2045-51. [PMID: 23737193 DOI: 10.1002/prot.24334] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 05/08/2013] [Indexed: 11/08/2022]
Abstract
EstU1 is a unique family VIII carboxylesterase that displays hydrolytic activity toward the amide bond of clinically used β-lactam antibiotics as well as the ester bond of p-nitrophenyl esters. EstU1 assumes a β-lactamase-like modular architecture and contains the residues Ser100, Lys103, and Tyr218, which correspond to the three catalytic residues (Ser64, Lys67, and Tyr150, respectively) of class C β-lactamases. The structure of the EstU1/cephalothin complex demonstrates that the active site of EstU1 is not ideally tailored to perform an efficient deacylation reaction during the hydrolysis of β-lactam antibiotics. This result explains the weak β-lactamase activity of EstU1 compared with class C β-lactamases. Finally, structural and sequential comparison of EstU1 with other family VIII carboxylesterases elucidates an operative molecular strategy used by family VIII carboxylesterases to extend their substrate spectrum.
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Affiliation(s)
- Sun-Shin Cha
- Marine Biotechnology Research Division, Korea Institute of Ocean Science and Technology, Ansan, 426-744, Republic of Korea; Ocean Science and Technology School, Korea Maritime University, Pusan, 606-791, Republic of Korea; Department of Marine Biotechnology, University of Science and Technology, Daejeon, 305-333, Republic of Korea
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21
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Dahyot S, Broutin I, de Champs C, Guillon H, Mammeri H. Contribution of asparagine 346 residue to the carbapenemase activity of CMY-2 β-lactamase. FEMS Microbiol Lett 2013; 345:147-53. [PMID: 23763375 DOI: 10.1111/1574-6968.12199] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2013] [Revised: 06/06/2013] [Accepted: 06/11/2013] [Indexed: 11/30/2022] Open
Abstract
Only a few plasmid-borne AmpC (pAmpC) β-lactamases, such as CMY-2, can account for carbapenem resistance in Enterobacteriaceae in combination with outer membrane impermeability. The aim of this study was to elucidate the contribution of Asn-346, which is well conserved among carbapenem-hydrolyzing pAmpCs, to the hydrolysis spectrum of CMY-2. Site-directed mutagenesis experiments were carried out to replace Asn-346 with glycine, alanine, valine, glutamate, aspartate, serine, threonine, glutamine, tyrosine, isoleucine, lysine, and histidine. The recombinant plasmids were transferred into wild-type and porin-deficient Escherichia coli strains. Asn-346 replacement reduced significantly the MICs of all β-lactams, except the Asn-346-Ile substitution that increased the MICs of cephalosporins, whereas it decreased those of carbapenems. The biochemical characterization, along with a molecular modeling study, showed that the size and the polarity of the side chain at position 346 assisted substrate binding and turnover. This study shows for the first time that the amino acid at position 346 contributes to the β-lactamase activity of cephalosporinases. Asparagine and isoleucine residues, which are well conserved at position 346 among AmpC-type enzymes, modulate their hydrolysis spectrum in an opposing sense. Ile-346 confers higher level of cephalosporins resistance, whereas Asn-346 confers carbapenem resistance in combination with outer membrane impermeability.
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Affiliation(s)
- Sandrine Dahyot
- Service de Bactériologie, Centre Hospitalo-Universitaire d'Amiens, Amiens, France
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22
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Fragment-guided design of subnanomolar β-lactamase inhibitors active in vivo. Proc Natl Acad Sci U S A 2012; 109:17448-53. [PMID: 23043117 DOI: 10.1073/pnas.1208337109] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fragment-based design was used to guide derivatization of a lead series of β-lactamase inhibitors that had heretofore resisted optimization for in vivo activity. X-ray structures of fragments overlaid with the lead suggested new, unanticipated functionality and points of attachment. Synthesis of three derivatives improved affinity over 20-fold and improved efficacy in cell culture. Crystal structures were consistent with the fragment-based design, enabling further optimization to a K(i) of 50 pM, a 500-fold improvement that required the synthesis of only six derivatives. One of these, compound 5, was tested in mice. Whereas cefotaxime alone failed to cure mice infected with β-lactamase-expressing Escherichia coli, 65% were cleared of infection when treated with a cefotaxime:5 combination. Fragment complexes offer a path around design hurdles, even for advanced molecules; the series described here may provide leads to overcome β-lactamase-based resistance, a key clinical challenge.
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23
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Ruble JF, Lefurgy ST, Cornish VW, Powers RA. Structural analysis of the Asn152Gly mutant of P99 cephalosporinase. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:1189-93. [PMID: 22948919 DOI: 10.1107/s0907444912024080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 05/26/2012] [Indexed: 11/10/2022]
Abstract
P99 cephalosporinase is a class C β-lactamase that is responsible in part for the widespread bacterial resistance to β-lactam antibiotics. Mutations of the conserved active-site residue Asn152 of the enzyme have been shown to alter β-lactam substrate specificity in vivo. Mutation of Asn152 to a glycine is notable in that it exhibits in vivo substrate-selectivity switching. In order to better understand the structural basis for this observed switch, the X-ray crystal structure of the apo Asn152Gly mutant of P99 was determined to 1.95 Å resolution. Unexpectedly, the artificial C-terminal His(6) tag of a symmetrically-related molecule was observed bound in the active site. The His(6) tag makes several interactions with key active-site residues, as well as with several sulfate ions. Additionally, the overall C-terminus occupies the space left vacant upon the mutation of Asn152 to glycine.
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Affiliation(s)
- James F Ruble
- Department of Chemistry, Grand Valley State University, Allendale, MI 49401, USA
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24
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Hydrolysis spectrum extension of CMY-2-like β-lactamases resulting from structural alteration in the Y-X-N loop. Antimicrob Agents Chemother 2012; 56:1151-6. [PMID: 22232281 DOI: 10.1128/aac.05630-11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Citrobacter freundii isolate CHA, which was responsible for postoperative peritonitis after 10 days of cefepime therapy, displayed a phenotype of resistance consistent with extended-spectrum AmpC (ESAC) β-lactamase. The chromosome-borne bla(AmpC-CHA) gene was amplified and sequenced, revealing five amino acid substitutions, I125V, R148H, Q196H, V305A, and V348A, in the product compared to the sequence of native AmpC. A cloning experiment yielded the Escherichia coli TOP10(pAmpC-CHA) strain, which was resistant to all extended-spectrum cephalosporins (ESCs), including cefepime. To ascertain whether the R148H substitution accounted for the hydrolysis spectrum extension, it was reverted by site-directed mutagenesis. The resulting E. coli TOP10(pAmpC-CHA-H148R) strain was fully susceptible to cefepime, thus confirming that the Arg-148 replacement was mandatory for substrate profile enlargement. To further characterize the phenotypical and biochemical effects induced by the R148H change, it was introduced by site-directed mutagenesis into the CMY-2 β-lactamase, which is structurally related to the chromosome-borne cephalosporinase of C. freundii. The CMY-2-R148H variant conferred increased MICs of ESCs, whereas those of carbapenems were unchanged even in a porin-deficient E. coli strain. Moreover, it exhibited increased catalytic efficiency (k(cat)/K(m)) toward ceftazidime (100-fold) due to an enhanced hydrolysis rate (k(cat)), whereas the enzymatic parameters toward imipenem were unchanged. The structural analysis of the AmpC variant showed that the R148H replacement occurred in the loop containing the Y-X-N motif, which is the counterpart of the SDN loop in class A β-lactamases. This study shows that the Y-X-N loop is a novel hot spot for mutations accounting for hydrolysis spectrum extension in CMY-2-type enzymes.
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25
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Kotsakis SD, Tzouvelekis LS, Petinaki E, Tzelepi E, Miriagou V. Effects of the Val211Gly substitution on molecular dynamics of the CMY-2 cephalosporinase: implications on hydrolysis of expanded-spectrum cephalosporins. Proteins 2011; 79:3180-92. [PMID: 21989938 DOI: 10.1002/prot.23150] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Revised: 07/04/2011] [Accepted: 07/14/2011] [Indexed: 11/05/2022]
Abstract
CMY-30, a naturally occurring class C β-lactamase differing from the Citrobacter freundii-derived CMY-2 by a Val211Gly substitution in the Ω-loop, exhibits increased hydrolytic efficiency against ceftazidime and cefotaxime. Kinetic constants of CMY-2 and CMY-30 against the latter substrates suggested that the improved efficiency of the Gly211 variant was due to an increase in k(cat). The structural basis of the increased turn-over rates of oxyimino-cephalosporins caused by Val211Gly was studied using 5 ns molecular dynamics simulations of CMY-2 and CMY-30 in their free forms and in covalent complexes with ceftazidime (acyl-enzyme) as well as a boronic acid analogue of ceftazidime (deacylation transition state). Analysis of thermal factors indicated that Val211Gly increased the flexibility of the Ω-loop/H7-helix and the Q120-loop formed by amino acids 112-125, and also altered the vibrations of the H10-helix/R2-loop. Structural elements containing the catalytic residues remained relatively rigid except Tyr150 in acyl-enzyme species. Regions exhibiting altered flexibility due to the substitution appear to move in a concerted manner in both enzymes. This movement was more intense in CMY-30 and also at directions different to those observed for CMY-2. Additionally, it appeared that the Val211Gly increased the available space for the accommodation of the R1 side chain of ceftazidime. These findings are likely associated with the significantly increased vibrations of the bound compounds observed in CMY-30 complexes. Therefore, the extended spectrum properties of CMY-30 seem to arise through a complex process implicating changes in protein movement and in the mode of substrate accommodation.
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Affiliation(s)
- Stathis D Kotsakis
- Laboratory of Bacteriology, Hellenic Pasteur Institute, 11521 Athens, Greece
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26
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Thiophenyl oxime-derived phosphonates as nano-molar class C beta-lactamase inhibitors reducing MIC of imipenem against Pseudomonas aeruginosa and Acinetobacter baumannii. Bioorg Med Chem Lett 2011; 21:4363-5. [PMID: 21664132 DOI: 10.1016/j.bmcl.2011.04.122] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 04/24/2011] [Accepted: 04/26/2011] [Indexed: 11/20/2022]
Abstract
The preparation and characterization of a series of thiophenyl oxime phosphonate beta-lactamase inhibitors is described. A number of these analogs were potent and selective inhibitors of class C beta-lactamases from Pseudomonas aeruginosa and Enterobacter cloacae. Compounds 3b and 7 reduced the MIC of imipenem against an AmpC expressing strain of imipenem-resistant P. aeruginosa. A number of the title compounds retained micromolar potency against the class D OXA-40 beta-lactamase from Acinetobacter baumannii and at high concentrations compound 3b was shown to reduce the MIC of imipenem against a highly imipenem-resistant strain of A. baumanii expressing the OXA-40 beta-lactamase. In mice compound 3b exhibited phamacokinetics similar to imipenem.
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27
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Wong WT, Au HW, Yap HK, Leung YC, Wong KY, Zhao Y. Structural studies of the mechanism for biosensing antibiotics in a fluorescein-labeled β-lactamase. BMC STRUCTURAL BIOLOGY 2011; 11:15. [PMID: 21443768 PMCID: PMC3076226 DOI: 10.1186/1472-6807-11-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 03/28/2011] [Indexed: 11/19/2022]
Abstract
Background β-lactamase conjugated with environment-sensitive fluorescein molecule to residue 166 on the Ω-loop near its catalytic site is a highly effective biosensor for β-lactam antibiotics. Yet the molecular mechanism of such fluorescence-based biosensing is not well understood. Results Here we report the crystal structure of a Class A β-lactamase PenP from Bacillus licheniformis 749/C with fluorescein conjugated at residue 166 after E166C mutation, both in apo form (PenP-E166Cf) and in covalent complex form with cefotaxime (PenP-E166Cf-cefotaxime), to illustrate its biosensing mechanism. In the apo structure the fluorescein molecule partially occupies the antibiotic binding site and is highly dynamic. In the PenP-E166Cf-cefatoxime complex structure the binding and subsequent acylation of cefotaxime to PenP displaces fluorescein from its original location to avoid steric clash. Such displacement causes the well-folded Ω-loop to become fully flexible and the conjugated fluorescein molecule to relocate to a more solvent exposed environment, hence enhancing its fluorescence emission. Furthermore, the fully flexible Ω-loop enables the narrow-spectrum PenP enzyme to bind cefotaxime in a mode that resembles the extended-spectrum β-lactamase. Conclusions Our structural studies indicate the biosensing mechanism of a fluorescein-labelled β-lactamase. Such findings confirm our previous proposal based on molecular modelling and provide useful information for the rational design of β-lactamase-based biosensor to detect the wide spectrum of β-lactam antibiotics. The observation of increased Ω-loop flexibility upon conjugation of fluorophore may have the potential to serve as a screening tool for novel β-lactamase inhibitors that target the Ω-loop and not the active site.
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Affiliation(s)
- Wai-Ting Wong
- Department of Applied Biology and Chemical Technology, Central Laboratory of Institute of Molecular Technology for Drug Discovery and Synthesis, The Hong Kong Polytechnic University, Hung Hom, Hong Hong, China
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Kawashima Y, Yasuhira K, Shibata N, Matsuura Y, Tanaka Y, Taniguchi M, Miyoshi Y, Takeo M, Kato DI, Higuchi Y, Negoro S. Enzymatic synthesis of nylon-6 units in organic solvents containing low concentrations of water. ACTA ACUST UNITED AC 2010. [DOI: 10.1016/j.molcatb.2010.02.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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29
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Endimiani A, Doi Y, Bethel CR, Taracila M, Adams-Haduch JM, O'Keefe A, Hujer AM, Paterson DL, Skalweit MJ, Page MGP, Drawz SM, Bonomo RA. Enhancing resistance to cephalosporins in class C beta-lactamases: impact of Gly214Glu in CMY-2. Biochemistry 2010; 49:1014-23. [PMID: 19938877 DOI: 10.1021/bi9015549] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The biochemical properties of CMY-32, a class C enzyme possessing a single-amino acid substitution in the Omega loop (Gly214Glu), were compared to those of the parent enzyme, CMY-2, a widespread class C beta-lactamase. In parallel with our microbiological characterization, the Gly214Glu substitution in CMY-32 reduced catalytic efficiency (k(cat)/K(m)) by 50-70% against "good" substrates (i.e., cephalothin) while increasing k(cat)/K(m) against "poor" substrates (i.e., cefotaxime). Additionally, CMY-32 was more susceptible to inactivation by sulfone beta-lactamase inhibitors (i.e., sulbactam and tazobactam) than CMY-2. Timed electrospray ionization mass spectrometry (ESI-MS) analysis of the reaction of CMY-2 and CMY-32 with different substrates and inhibitors suggested that both beta-lactamases formed similar intermediates during catalysis and inactivation. We next showed that the carbapenems (imipenem, meropenem, and doripenem) form long-lived acyl-enzyme intermediates and present evidence that there is beta-lactamase-catalyzed elimination of the C(6) hydroxyethyl substituent. Furthermore, we discovered that the monobactam aztreonam and BAL29880, a new beta-lactamase inhibitor of the monobactam class, inactivate CMY-2 and CMY-32 by forming an acyl-enzyme intermediate that undergoes elimination of SO(3)(2-). Molecular modeling and dynamics simulations suggest that the Omega loop is more constrained in CMY-32 than CMY-2. Our model also proposes that Gln120 adopts a novel conformation in the active site while new interactions form between Glu214 and Tyr221, thus explaining the increased level of cefotaxime hydrolysis. When it is docked in the active site, we observe that BAL29880 exploits contacts with highly conserved residues Lys67 and Asn152 in CMY-2 and CMY-32. These findings highlight (i) the impact of single-amino acid substitutions on protein evolution in clinically important AmpC enzymes and (ii) the novel insights into the mechanisms by which carbapenems and monobactams interact with CMY-2 and CMY-32 beta-lactamases.
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Affiliation(s)
- Andrea Endimiani
- Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio 44106, USA
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30
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Abstract
Since the introduction of penicillin, beta-lactam antibiotics have been the antimicrobial agents of choice. Unfortunately, the efficacy of these life-saving antibiotics is significantly threatened by bacterial beta-lactamases. beta-Lactamases are now responsible for resistance to penicillins, extended-spectrum cephalosporins, monobactams, and carbapenems. In order to overcome beta-lactamase-mediated resistance, beta-lactamase inhibitors (clavulanate, sulbactam, and tazobactam) were introduced into clinical practice. These inhibitors greatly enhance the efficacy of their partner beta-lactams (amoxicillin, ampicillin, piperacillin, and ticarcillin) in the treatment of serious Enterobacteriaceae and penicillin-resistant staphylococcal infections. However, selective pressure from excess antibiotic use accelerated the emergence of resistance to beta-lactam-beta-lactamase inhibitor combinations. Furthermore, the prevalence of clinically relevant beta-lactamases from other classes that are resistant to inhibition is rapidly increasing. There is an urgent need for effective inhibitors that can restore the activity of beta-lactams. Here, we review the catalytic mechanisms of each beta-lactamase class. We then discuss approaches for circumventing beta-lactamase-mediated resistance, including properties and characteristics of mechanism-based inactivators. We next highlight the mechanisms of action and salient clinical and microbiological features of beta-lactamase inhibitors. We also emphasize their therapeutic applications. We close by focusing on novel compounds and the chemical features of these agents that may contribute to a "second generation" of inhibitors. The goal for the next 3 decades will be to design inhibitors that will be effective for more than a single class of beta-lactamases.
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Affiliation(s)
- Sarah M. Drawz
- Departments of Pathology, Medicine, Pharmacology, Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio, Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio
| | - Robert A. Bonomo
- Departments of Pathology, Medicine, Pharmacology, Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, Ohio, Research Service, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio
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31
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Thomas VL, McReynolds AC, Shoichet BK. Structural bases for stability-function tradeoffs in antibiotic resistance. J Mol Biol 2009; 396:47-59. [PMID: 19913034 DOI: 10.1016/j.jmb.2009.11.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/02/2009] [Accepted: 11/04/2009] [Indexed: 10/20/2022]
Abstract
Preorganization of enzyme active sites for substrate recognition typically comes at a cost to the stability of the folded form of the protein; consequently, enzymes can be dramatically stabilized by substitutions that attenuate the size and preorganization "strain" of the active site. How this stability-activity tradeoff constrains enzyme evolution has remained less certain, and it is unclear whether one should expect major stability insults as enzymes mutate towards new activities or how these new activities manifest structurally. These questions are both germane and easy to study in beta-lactamases, which are evolving on the timescale of years to confer resistance to an ever-broader spectrum of beta-lactam antibiotics. To explore whether stability is a substantial constraint on this antibiotic resistance evolution, we investigated extended-spectrum mutants of class C beta-lactamases, which had evolved new activity versus third-generation cephalosporins. Five mutant enzymes had between 100-fold and 200-fold increased activity against the antibiotic cefotaxime in enzyme assays, and the mutant enzymes all lost thermodynamic stability (from 1.7 kcal mol(-)(1) to 4.1 kcal mol(-)(1)), consistent with the stability-function hypothesis. Intriguingly, several of the substitutions were 10-20 A from the catalytic serine; the question of how they conferred extended-spectrum activity arose. Eight structures, including complexes with inhibitors and extended-spectrum antibiotics, were determined by X-ray crystallography. Distinct mechanisms of action, including changes in the flexibility and ground-state structures of the enzyme, are revealed for each mutant. These results explain the structural bases for the antibiotic resistance conferred by these substitutions and their corresponding decrease in protein stability, which will constrain the evolution of new antibiotic resistance.
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Affiliation(s)
- Veena L Thomas
- Graduate Program in Pharmaceutical Sciences and Pharmacogenomics, University of California San Francisco, San Francisco, CA 94158-2518, USA
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32
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Yasuhira K, Shibata N, Mongami G, Uedo Y, Atsumi Y, Kawashima Y, Hibino A, Tanaka Y, Lee YH, Kato DI, Takeo M, Higuchi Y, Negoro S. X-ray crystallographic analysis of the 6-aminohexanoate cyclic dimer hydrolase: catalytic mechanism and evolution of an enzyme responsible for nylon-6 byproduct degradation. J Biol Chem 2009; 285:1239-48. [PMID: 19889645 DOI: 10.1074/jbc.m109.041285] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We performed x-ray crystallographic analyses of the 6-aminohexanoate cyclic dimer (Acd) hydrolase (NylA) from Arthrobacter sp., an enzyme responsible for the degradation of the nylon-6 industry byproduct. The fold adopted by the 472-amino acid polypeptide generated a compact mixed alpha/beta fold, typically found in the amidase signature superfamily; this fold was especially similar to the fold of glutamyl-tRNA(Gln) amidotransferase subunit A (z score, 49.4) and malonamidase E2 (z score, 44.8). Irrespective of the high degree of structural similarity to the typical amidase signature superfamily enzymes, the specific activity of NylA for glutamine, malonamide, and indoleacetamide was found to be lower than 0.5% of that for Acd. However, NylA possessed carboxylesterase activity nearly equivalent to the Acd hydrolytic activity. Structural analysis of the inactive complex between the activity-deficient S174A mutant of NylA and Acd, performed at 1.8 A resolution, suggested the following enzyme/substrate interactions: a Ser(174)-cis-Ser(150)-Lys(72) triad constitutes the catalytic center; the backbone N in Ala(171) and Ala(172) are involved in oxyanion stabilization; Cys(316)-S(gamma) forms a hydrogen bond with nitrogen (Acd-N(7)) at the uncleaved amide bond in two equivalent amide bonds of Acd. A single S174A, S150A, or K72A substitution in NylA by site-directed mutagenesis decreased the Acd hydrolytic and esterolytic activities to undetectable levels, indicating that Ser(174)-cis-Ser(150)-Lys(72) is essential for catalysis. In contrast, substitutions at position 316 specifically affected Acd hydrolytic activity, suggesting that Cys(316) is responsible for Acd binding. On the basis of the structure and functional analysis, we discussed the catalytic mechanisms and evolution of NylA in comparison with other Ser-reactive hydrolases.
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Affiliation(s)
- Kengo Yasuhira
- Department of Materials Science and Chemistry, Graduate School of Engineering, University of Hyogo, Hyogo 671-2201, Japan
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33
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Ohki T, Shibata N, Higuchi Y, Kawashima Y, Takeo M, Kato DI, Negoro S. Two alternative modes for optimizing nylon-6 byproduct hydrolytic activity from a carboxylesterase with a beta-lactamase fold: X-ray crystallographic analysis of directly evolved 6-aminohexanoate-dimer hydrolase. Protein Sci 2009; 18:1662-73. [PMID: 19521995 DOI: 10.1002/pro.185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Promiscuous 6-aminohexanoate-linear dimer (Ald)-hydrolytic activity originally obtained in a carboxylesterase with a beta-lactamase fold was enhanced about 80-fold by directed evolution using error-prone PCR and DNA shuffling. Kinetic studies of the mutant enzyme (Hyb-S4M94) demonstrated that the enzyme had acquired an increased affinity (K(m) = 15 mM) and turnover (k(cat) = 3.1 s(-1)) for Ald, and that a catalytic center suitable for nylon-6 byproduct hydrolysis had been generated. Construction of various mutant enzymes revealed that the enhanced activity in the newly evolved enzyme is due to the substitutions R187S/F264C/D370Y. Crystal structures of Hyb-S4M94 with bound substrate suggested that catalytic function for Ald was improved by hydrogen-bonding/hydrophobic interactions between the Ald--COOH and Tyr370, a hydrogen-bonding network from Ser187 to Ald--NH(3) (+), and interaction between Ald--NH(3) (+) and Gln27-O(epsilon) derived from another subunit in the homo-dimeric structure. In wild-type Ald-hydrolase (NylB), Ald-hydrolytic activity is thought to be optimized by the substitutions G181D/H266N, which improve an electrostatic interaction with Ald--NH(3) (+) (Kawashima et al., FEBS J 2009; 276:2547-2556). We propose here that there exist at least two alternative modes for optimizing the Ald-hydrolytic activity of a carboxylesterase with a beta-lactamase fold.
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Affiliation(s)
- Taku Ohki
- Department of Materials Science and Chemistry, Graduate School of Engineering, University of Hyogo, Hyogo 671-2280, Japan
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34
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Kotsakis SD, Papagiannitsis CC, Tzelepi E, Tzouvelekis LS, Miriagou V. Extended-spectrum properties of CMY-30, a Val211Gly mutant of CMY-2 cephalosporinase. Antimicrob Agents Chemother 2009; 53:3520-3. [PMID: 19470510 PMCID: PMC2715598 DOI: 10.1128/aac.00219-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 05/03/2009] [Accepted: 05/17/2009] [Indexed: 01/25/2023] Open
Abstract
CMY-30, a Val211Gly mutant of CMY-2 cephalosporinase, was derived by mutagenesis. The hydrolytic efficiency of CMY-30 against expanded-spectrum cephalosporins was higher than that of CMY-2 due to increased k(cat) values. Findings indicate a role of the Omega loop residue 211 in determining the substrate specificities of CMYs also corroborated by modeling studies.
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Affiliation(s)
- Stathis D Kotsakis
- Laboratory of Bacteriology, Hellenic Pasteur Institute, Vas. Sofias 127, Athens 11521, Greece
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35
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Yamaguchi Y, Sato G, Yamagata Y, Doi Y, Wachino JI, Arakawa Y, Matsuda K, Kurosaki H. Structure of AmpC beta-lactamase (AmpCD) from an Escherichia coli clinical isolate with a tripeptide deletion (Gly286-Ser287-Asp288) in the H10 helix. Acta Crystallogr Sect F Struct Biol Cryst Commun 2009; 65:540-3. [PMID: 19478427 PMCID: PMC2688406 DOI: 10.1107/s1744309109014249] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2008] [Accepted: 04/16/2009] [Indexed: 11/10/2022]
Abstract
The X-ray crystal structure of AmpC beta-lactamase (AmpC(D)) with a tripeptide deletion (Gly286-Ser287-Asp288) produced by Escherichia coli HKY28, a ceftazidime-resistant strain, was determined at a resolution of 1.7 A. The structure of AmpC(D) suggests that the tripeptide deletion at positions 286-288 located in the H10 helix causes a structural change of the Asn289-Asn294 region from the alpha-helix present in the native AmpC beta-lactamase of E. coli to a loop structure, which results in a widening of the substrate-binding site.
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Affiliation(s)
- Yoshihiro Yamaguchi
- Environmental Safety Center, Kumamoto University, 39-1 Kurokami 2-chome, Kumamoto 860-8555, Japan
| | - Genta Sato
- Department of Structure–Function Physical Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan
| | - Yuriko Yamagata
- Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan
| | - Yohei Doi
- Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan
| | - Jun-ichi Wachino
- Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan
| | - Yoshichika Arakawa
- Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan
| | - Koki Matsuda
- Department of Structure–Function Physical Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan
| | - Hiromasa Kurosaki
- Department of Structure–Function Physical Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, Oe-honmachi 5-1, Kumamoto 862-0973, Japan
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36
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Biological Activity of Aminophosphonic Acids and Their Short Peptides. TOPICS IN HETEROCYCLIC CHEMISTRY 2009. [DOI: 10.1007/7081_2008_14] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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37
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CMY-31 and CMY-36 cephalosporinases encoded by ColE1-like plasmids. Antimicrob Agents Chemother 2008; 53:1256-9. [PMID: 19104021 DOI: 10.1128/aac.01284-08] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two CMY-2 derivatives, CMY-31 (Gln(215)-->Arg) from Salmonella enterica serotype Newport and CMY-36 (Ala(77)-->Cys and Gln(193)-->Glu) from Klebsiella pneumoniae, were characterized. Both cephalosporinases functionally resembled CMY-2. bla(CMY) alleles occurred as parts of a putative transposon comprising ISEcp1B and a Citrobacter freundii-derived sequence carried by ColE1-like plasmids similar to CMY-5-encoding pTKH11 from Klebsiella oxytoca.
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38
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Fenollar-Ferrer C, Frau J, Donoso J, Muñoz F. Evolution of class C β-lactamases: factors influencing their hydrolysis and recognition mechanisms. Theor Chem Acc 2008. [DOI: 10.1007/s00214-008-0463-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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Kalp M, Sheri A, Buynak JD, Bethel CR, Bonomo RA, Carey PR. Efficient inhibition of class A and class D beta-lactamases by Michaelis complexes. J Biol Chem 2007; 282:21588-91. [PMID: 17561511 DOI: 10.1074/jbc.c700080200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A 6-alkylidiene penam sulfone, SA-1-204, is an efficient inhibitor of both SHV-1 and OXA-1 beta-lactamases with K(I) = 42 +/- 4 nm and 1.0 +/- 0.1 microm, respectively. To gain insight into the reaction chemistry of SA-1-204, the reactions between this inhibitor and SHV-1 and OXA-1 were studied by Raman spectroscopy in single crystals and in solution. Raman signatures characteristic of the unreacted beta-lactam ring show that in both phases the inhibitor binds as a noncovalent Michaelis-like complex. This complex is present as the major population for periods of up to an hour. On longer time scales, the Raman data show that beta-lactam ring opening eventually leads to a complex mixture of reaction products. However, the data clearly demonstrate that the key species for inhibition on the time scale of bacterial half-lives is the noncovalent complex preceding acylation.
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Affiliation(s)
- Matthew Kalp
- Department of Biochemistry, Case Western Reserve University, Cleveland, OH 44106, USA
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40
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Negoro S, Ohki T, Shibata N, Sasa K, Hayashi H, Nakano H, Yasuhira K, Kato DI, Takeo M, Higuchi Y. Nylon-oligomer Degrading Enzyme/Substrate Complex: Catalytic Mechanism of 6-Aminohexanoate-dimer Hydrolase. J Mol Biol 2007; 370:142-56. [DOI: 10.1016/j.jmb.2007.04.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2006] [Revised: 04/05/2007] [Accepted: 04/17/2007] [Indexed: 10/23/2022]
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41
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Hata M, Fujii Y, Tanaka Y, Ishikawa H, Ishii M, Neya S, Tsuda M, Hoshino T. Substrate deacylation mechanisms of serine-beta-lactamases. Biol Pharm Bull 2007; 29:2151-9. [PMID: 17077507 DOI: 10.1248/bpb.29.2151] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The substrate deacylation mechanisms of serine-beta-lactamases (classes A, C and D) were investigated by theoretical calculations. The deacylation of class A proceeds via four elementary reactions. The rate-determining process is the tetrahedral intermediate (TI) formation and the activation energy is 24.6 kcal/mol at the DFT level. The deacylation does not proceed only by Glu166, which acts as a general base, but Lys73 also participates in the reaction. The C3-carboxyl group of the substrate reduces the barrier height at the TI formation (substrate-assisted catalysis). In the case of class C, the deacylation consists of two elementary processes. The activation energy of the TI formation has been estimated to be 30.5 kcal/mol. Tyr150Oeta is stabilized in the deprotonated state in the acyl-enzyme complex and works as a general base. This situation can exist due to the interaction with two positively charged side chains of lysine (Lys67 and Lys315). The deacylation of class D also consists of two elementary reaction processes. The activation energy of the TI formation is ca. 30 kcal/mol. It is thought that the side chain of Lys70 is deprotonated and acts as a general base. When Lys70 is carbamylated, the activation energy is reduced to less than 20 kcal/mol. This suggests that the high hydrolysis activity of class D with carbamylated Lys70 is due to the reduction of activation energy for deacylation. From these results, it is concluded that the contribution of the lysine residue adjacent to the serine residue is indispensable for the enzymatic reactions by serine-beta-lactamases.
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Affiliation(s)
- Masayuki Hata
- Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Japan.
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42
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Okazaki S, Suzuki A, Komeda H, Yamaguchi S, Asano Y, Yamane T. Crystal structure and functional characterization of a D-stereospecific amino acid amidase from Ochrobactrum anthropi SV3, a new member of the penicillin-recognizing proteins. J Mol Biol 2006; 368:79-91. [PMID: 17331533 DOI: 10.1016/j.jmb.2006.10.070] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 10/19/2006] [Accepted: 10/20/2006] [Indexed: 11/28/2022]
Abstract
D-amino acid amidase (DAA) from Ochrobactrum anthropi SV3, which catalyzes the stereospecific hydrolysis of D-amino acid amides to yield the D-amino acid and ammonia, has attracted increasing attention as a catalyst for the stereospecific production of D-amino acids. In order to clarify the structure-function relationships of DAA, the crystal structures of native DAA, and of the D-phenylalanine/DAA complex, were determined at 2.1 and at 2.4 A resolution, respectively. Both crystals contain six subunits (A-F) in the asymmetric unit. The fold of DAA is similar to that of the penicillin-recognizing proteins, especially D-alanyl-D-alanine-carboxypeptidase from Streptomyces R61, and class C beta-lactamase from Enterobacter cloacae strain GC1. The catalytic residues of DAA and the nucleophilic water molecule for deacylation were assigned based on these structures. DAA has a flexible Omega-loop, similar to class C beta-lactamase. DAA forms a pseudo acyl-enzyme intermediate between Ser60 O(gamma) and the carbonyl moiety of d-phenylalanine in subunits A, B, C, D, and E, but not in subunit F. The difference between subunit F and the other subunits (A, B, C, D and E) might be attributed to the order/disorder structure of the Omega-loop: the structure of this loop cannot assigned in subunit F. Deacylation of subunit F may be facilitated by the relative movement of deprotonated His307 toward Tyr149. His307 N(epsilon2) extracts the proton from Tyr149 O(eta), then Tyr149 O(eta) attacks a nucleophilic water molecule as a general base. Gln214 on the Omega-loop is essential for forming a network of water molecules that contains the nucleophilic water needed for deacylation. Although peptidase activity is found in almost all penicillin-recognizing proteins, DAA lacks peptidase activity. The lack of transpeptidase and carboxypeptidase activities may be attributed to steric hindrance of the substrate-binding pocket by a loop comprised of residues 278-290 and the Omega-loop.
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Affiliation(s)
- Seiji Okazaki
- Department of Biotechnology, School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan
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43
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Kim JY, Jung HI, An YJ, Lee JH, Kim SJ, Jeong SH, Lee KJ, Suh PG, Lee HS, Lee SH, Cha SS. Structural basis for the extended substrate spectrum of CMY-10, a plasmid-encoded class C beta-lactamase. Mol Microbiol 2006; 60:907-16. [PMID: 16677302 DOI: 10.1111/j.1365-2958.2006.05146.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The emergence and dissemination of extended-spectrum (ES) beta-lactamases induce therapeutic failure and a lack of eradication of clinical isolates even by third-generation beta-lactam antibiotics like ceftazidime. CMY-10 is a plasmid-encoded class C beta-lactamase with a wide spectrum of substrates. Unlike the well-studied class C ES beta-lactamase from Enterobacter cloacae GC1, the Omega-loop does not affect the active site conformation and the catalytic activity of CMY-10. Instead, a three-amino-acid deletion in the R2-loop appears to be responsible for the ES activity of CMY-10. According to the crystal structure solved at 1.55 A resolution, the deletion significantly widens the R2 active site, which accommodates the R2 side-chains of beta-lactam antibiotics. This observation led us to demonstrate the hydrolysing activity of CMY-10 towards imipenem with a long R2 substituent. The forced mutational analyses of P99 beta-lactamase reveal that the introduction of deletion mutations into the R2-loop is able to extend the substrate spectrum of class C non-ES beta-lactamases, which is compatible with the isolation of natural class C ES enzymes harbouring deletion mutations in the R2-loop. Consequently, the opening of the R2 active site by the deletion of some residues in the R2-loop can be considered as an operative molecular strategy of class C beta-lactamases to extend their substrate spectrum.
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Affiliation(s)
- Jae Young Kim
- School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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Carter BT, Lin H, Goldberg SD, Althoff EA, Raushel J, Cornish VW. Investigation of the mechanism of resistance to third-generation cephalosporins by class C beta-lactamases by using chemical complementation. Chembiochem 2006; 6:2055-67. [PMID: 16250067 DOI: 10.1002/cbic.200500058] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The widespread use of antibiotics to treat bacterial infections has led to the continuing challenge of antibiotic resistance. For beta-lactam antibiotics, the most common form of resistance is the expression of beta-lactamase enzymes, which inactivate the antibiotics by cleavage of the beta-lactam core. In this study, chemical complementation, which is a general method to link the formation or cleavage of a chemical bond to the transcription of a reporter gene in vivo, was employed in combination with combinatorial mutagenesis to study the mechanism by which the class C beta-lactamase P99 might evolve resistance to the commonly administered third-generation cephalosporin cefotaxime. The chemical complementation system was first shown to be able to distinguish between the wild-type (wt) class C beta-lactamase P99 and the clinically isolated extended-spectrum class C beta-lactamase GC1 in the presence of cefotaxime. The system was then employed to evaluate the activity of mutants of wt P99 towards cefotaxime. A number of single-point mutations at position 221 (Tyr in wt P99) were identified that conferred resistance towards inhibition by cefotaxime, with as much as a 2000-fold increase in k(cat) and a 100-fold increase in k(cat)/K(M) (k(cat)=the rate of catalysis; K(M)=the Michaelis constant), as compared to those of the wt enzyme. Finally, the chemical complementation system was employed in a high-throughput screen to identify a number of mutants of P99 that have multiple mutations around the substrate-binding pocket that increase resistance towards cefotaxime inhibition. The catalytic turnover of cefotaxime by the most active mutant identified was 5500 times higher than that of the wt P99. The resistant mutants suggest a mechanism by which a number of mutations can confer resistance by increasing the flexibility of the Omega loop and altering the positioning of residue 221. Thus, as illustrated in this study, chemical complementation has the potential to be used as a high-throughput screen to study a wide range of enzyme-drug interactions.
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Affiliation(s)
- Brian T Carter
- Department of Chemistry, Columbia University, New York, NY 10027, USA
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45
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Bauvois C, Ibuka AS, Celso A, Alba J, Ishii Y, Frère JM, Galleni M. Kinetic properties of four plasmid-mediated AmpC beta-lactamases. Antimicrob Agents Chemother 2006; 49:4240-6. [PMID: 16189104 PMCID: PMC1251510 DOI: 10.1128/aac.49.10.4240-4246.2005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The heterologous production in Escherichia coli, the purification, and the kinetic characterization of four plasmid-encoded class C beta-lactamases (ACT-1, MIR-1, CMY-2, and CMY-1) were performed. Except for their instability, these enzymes are very similar to the known chromosomally encoded AmpC beta-lactamases. Their kinetic parameters did not show major differences from those obtained for the corresponding chromosomal enzymes. However, the K(m) values of CMY-2 for cefuroxime, cefotaxime, and oxacillin were significantly decreased compared to those of the chromosomal AmpC enzymes. Finally, the susceptibility patterns of different E. coli hosts producing a plasmid- or a chromosome-encoded class C enzyme toward beta-lactam antibiotics are mainly due to the overproduction of the beta-lactamase in the periplasmic space of the bacteria rather than to a specific catalytic profile of the plasmid-encoded beta-lactamases.
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Affiliation(s)
- Cédric Bauvois
- Centre d'Ingénierie des Protéines, B6 Sart Tilman, Université de Liège, Belgium
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46
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Díaz N, Suárez D, Sordo TL. Molecular Dynamics Simulations of Class C β-Lactamase from Citrobacter freundii: Insights into the Base Catalyst for Acylation. Biochemistry 2005; 45:439-51. [PMID: 16401074 DOI: 10.1021/bi051600j] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Herein, we present results from molecular dynamics (MD) simulations of the class C beta-lactamase from Citrobacter freundii and its Michaelis complex with aztreonam. Four different configurations of the active site were modeled in aqueous solution, and their relative stability was estimated by means of quantum mechanical energy calculations. For the free enzyme, the energetically most stable configurations present a neutral Lys67 residue or an anionic Tyr150 side chain. Our calculations predict that these two configurations are quite close in terms of free energy, the anionic Tyr150 state being favored by approximately 1 kcal/mol. In contrast, for the noncovalent complex formed between the C. freundii enzyme and aztreonam, the energetic analyses predict that the configuration with the neutral Lys67 residue is much more stable than the anionic Tyr150 one (approximately 20 kcal/mol). Moreover, the MD simulations reveal that the neutral Lys67 state results in a proper enzyme-aztreonam orientation for nucleophilic attack and in a very stable contact between the nucleophilic hydroxyl group of Ser64 and the neutral amino side chain of Lys67. Thus, both the computed free energies and the structural analyses support the assignation of Lys67 as the base catalyst for the acylation step in the native form of the C. freundii enzyme.
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Affiliation(s)
- Natalia Díaz
- Departamento de Química Física y Analítica, Universidad de Oviedo, C/Julián Clavería, 8, 33006 Oviedo, Asturias, Spain.
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48
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Hata M, Tanaka Y, Fujii Y, Neya S, Hoshino T. A Theoretical Study on the Substrate Deacylation Mechanism of Class C β-Lactamase. J Phys Chem B 2005; 109:16153-60. [PMID: 16853052 DOI: 10.1021/jp045403q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The whole reaction of the deacylation of class C beta-lactamase was investigated by performing quantum chemical calculations under physiological conditions. In this study, the X-ray crystallographic structure of the inhibitor moxalactam-bound class C beta-lactamase (Patera et al. J. Am. Chem. Soc. 2000, 122, 10504-10512.) was utilized and moxalactam was changed into the substrate cefaclor. A model for quantum chemical calculations was constructed using an energy-minimized structure of the substrate-bound enzyme obtained by molecular mechanics calculation, in which the enzyme was soaked in thousands of TIP3P water molecules. It was found that the deacylation reaction consisted of two elementary processes. The first process was formation of a tetrahedral intermediate, which was initiated by the activation of catalytic water by Tyr150, and the second process was detachment of the hydroxylated substrate from the enzyme, which associated with proton transfer from the side chain of Lys67 to Ser64O(gamma). The first process is a rate-determining process, and the activation energy was estimated to be 30.47 kcal/mol from density functional theory calculations considering electron correlation (B3LYP/6-31G**). The side chain of Tyr150 was initially in a deprotonated state and was stably present in the active site of the acyl-enzyme complex, being held by Lys67 and Lys315 cooperatively.
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Affiliation(s)
- Masayuki Hata
- Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 263-8522, Japan.
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49
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Michaux C, Charlier P, Frère JM, Wouters J. Crystal structure of BRL 42715, C6-(N1-methyl-1,2,3-triazolylmethylene)penem, in complex with Enterobacter cloacae 908R beta-lactamase: evidence for a stereoselective mechanism from docking studies. J Am Chem Soc 2005; 127:3262-3. [PMID: 15755127 DOI: 10.1021/ja0426241] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BRL 42715, C6-(N1-methyl-1,2,3-triazolylmethylene)penem, is an active-site-directed inactivator of bacterial beta-lactamases. The crystal structure of Enterobacter cloacae 908R class C beta-lactamase in complex with BRL 42715, docking, and energy minimization studies explain stereoselectivity of the binding of C6-(heterocyclic methylene)penems against class C beta-lactamase.
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Affiliation(s)
- Catherine Michaux
- Laboratoire de Chimie Biologique Structurale, Université of Namur, 5000 Namur, Belgium
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Fenollar-Ferrer C, Donoso J, Frau J, Muñoz F. Molecular Modeling ofHenry-Michaelis and Acyl-Enzyme Complexes between Imipenem andEnterobacter cloacae P99β-Lactamase. Chem Biodivers 2005; 2:645-56. [PMID: 17192008 DOI: 10.1002/cbdv.200590041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We report a molecular-mechanics (AMBER*) study on the Henry-Michaelis complex and the corresponding acyl-enzyme adduct formed between imipenem (1), a transient inhibitor of beta-lactamases, and Enterobacter cloacae P99, a class C-beta-lactamase. We have examined the influence of the structural configuration of the functional groups in the substrate on their three-dimensional (3D) arrangement at the active site, which was compared with those adopted by typical penicillins and cephalosporins. Our results confirm that the carboxy group of the antibiotic plays a prominent role in the binding of the substrate to the active site, and that it activates Ser64 through interaction with the phenolic OH group of Tyr150. The binding of imipenem to E. cloacae P99 increases the distance between Tyr150 and Ser64 due to the presence of a hydrophobic Me group in the (R)-1-hydroxyethyl substituent at C(6). This, together with the 3D arrangement of its carboxy group, leads to an interaction with the active site in a manner that hinders H+ exchange between the nucleophile in Ser64 and its basic activator, the phenolic group of Tyr150.
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Affiliation(s)
- Cristina Fenollar-Ferrer
- Instituto Universitario de Investigación en Ciencias de la Salud, Departamento de Química, Universidad de las Islas Baleares, Ctra. de Vallemossa km 7.5, 07122 Palma de Mallorca, Spain
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