1
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Zhao Z, Shen X, Chen S, Gu J, Wang H, Mojica MF, Samanta M, Bhowmik D, Vila AJ, Bonomo RA, Haider S. Gating interactions steer loop conformational changes in the active site of the L1 metallo-β-lactamase. eLife 2023; 12:e83928. [PMID: 36826989 PMCID: PMC9977270 DOI: 10.7554/elife.83928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 02/03/2023] [Indexed: 02/25/2023] Open
Abstract
β-Lactam antibiotics are the most important and widely used antibacterial agents across the world. However, the widespread dissemination of β-lactamases among pathogenic bacteria limits the efficacy of β-lactam antibiotics. This has created a major public health crisis. The use of β-lactamase inhibitors has proven useful in restoring the activity of β-lactam antibiotics, yet, effective clinically approved inhibitors against class B metallo-β-lactamases are not available. L1, a class B3 enzyme expressed by Stenotrophomonas maltophilia, is a significant contributor to the β-lactam resistance displayed by this opportunistic pathogen. Structurally, L1 is a tetramer with two elongated loops, α3-β7 and β12-α5, present around the active site of each monomer. Residues in these two loops influence substrate/inhibitor binding. To study how the conformational changes of the elongated loops affect the active site in each monomer, enhanced sampling molecular dynamics simulations were performed, Markov State Models were built, and convolutional variational autoencoder-based deep learning was applied. The key identified residues (D150a, H151, P225, Y227, and R236) were mutated and the activity of the generated L1 variants was evaluated in cell-based experiments. The results demonstrate that there are extremely significant gating interactions between α3-β7 and β12-α5 loops. Taken together, the gating interactions with the conformational changes of the key residues play an important role in the structural remodeling of the active site. These observations offer insights into the potential for novel drug development exploiting these gating interactions.
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Affiliation(s)
- Zhuoran Zhao
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
| | - Xiayu Shen
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
| | - Shuang Chen
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
| | - Jing Gu
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
| | - Haun Wang
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
| | - Maria F Mojica
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of MedicineClevelandUnited States
- Louis Stokes Cleveland Department of Veterans Affairs Medical CenterClevelandUnited States
- CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES)ClevelandUnited States
| | - Moumita Samanta
- College of Computing, Georgia Institute of TechnologyAtlantaUnited States
| | - Debsindhu Bhowmik
- Computer Science and Engineering Division, Oak Ridge National LaboratoriesOak RidgeUnited States
| | - Alejandro J Vila
- CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES)ClevelandUnited States
- Laboratorio de Metaloproteínas, Instituto de Biología Molecular y Celular de Rosario (IBR, CONICET-UNR)RosarioArgentina
- Area Biofísica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de RosarioRosarioArgentina
| | - Robert A Bonomo
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of MedicineClevelandUnited States
- Louis Stokes Cleveland Department of Veterans Affairs Medical CenterClevelandUnited States
- CWRU-Cleveland VAMC Center for Antimicrobial Resistance and Epidemiology (Case VA CARES)ClevelandUnited States
- Departments of Medicine, Biochemistry, Pharmacology, and Proteomics and Bioinformatics, Case Western Reserve University School of MedicineClevelandUnited States
| | - Shozeb Haider
- Department of Pharmaceutical and Biological Chemistry, School of Pharmacy, University College LondonLondonUnited Kingdom
- UCL Centre for Advanced Research Computing, University College LondonLondonUnited Kingdom
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2
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Cheng Q, DeYonker NJ. Acylation and deacylation mechanism and kinetics of penicillin G reaction with Streptomyces R61 DD-peptidase. J Comput Chem 2020; 41:1685-1697. [PMID: 32323874 DOI: 10.1002/jcc.26210] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 02/26/2020] [Accepted: 04/05/2020] [Indexed: 12/20/2022]
Abstract
Two quantum mechanical (QM)-cluster models are built for studying the acylation and deacylation mechanism and kinetics of Streptomyces R61 DD-peptidase with the penicillin G at atomic level detail. DD-peptidases are bacterial enzymes involved in the cross-linking of peptidoglycan to form the cell wall, necessary for bacterial survival. The cross-linking can be inhibited by antibiotic beta-lactam derivatives through acylation, preventing the acyl-enzyme complex from undergoing further deacylation. The deacylation step was predicted to be rate-limiting. Transition state and intermediate structures are found using density functional theory in this study, and thermodynamic and kinetic properties of the proposed mechanism are evaluated. The acyl-enzyme complex is found lying in a deep thermodynamic sink, and deacylation is indeed the severely rate-limiting step, leading to suicide inhibition of the peptidoglycan cross-linking. The usage of QM-cluster models is a promising technique to understand, improve, and design antibiotics to disrupt function of the Streptomyces R61 DD-peptidase.
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Affiliation(s)
- Qianyi Cheng
- Department of Chemistry, University of Memphis, Memphis, Tennessee, USA
| | - Nathan J DeYonker
- Department of Chemistry, University of Memphis, Memphis, Tennessee, USA
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3
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Mechanism of proton transfer in class A β-lactamase catalysis and inhibition by avibactam. Proc Natl Acad Sci U S A 2020; 117:5818-5825. [PMID: 32123084 DOI: 10.1073/pnas.1922203117] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Gram-negative bacteria expressing class A β-lactamases pose a serious health threat due to their ability to inactivate all β-lactam antibiotics. The acyl-enzyme intermediate is a central milestone in the hydrolysis reaction catalyzed by these enzymes. However, the protonation states of the catalytic residues in this complex have never been fully analyzed experimentally due to inherent difficulties. To help unravel the ambiguity surrounding class A β-lactamase catalysis, we have used ultrahigh-resolution X-ray crystallography and the recently approved β-lactamase inhibitor avibactam to trap the acyl-enzyme complex of class A β-lactamase CTX-M-14 at varying pHs. A 0.83-Å-resolution CTX-M-14 complex structure at pH 7.9 revealed a neutral state for both Lys73 and Glu166. Furthermore, the avibactam hydroxylamine-O-sulfonate group conformation varied according to pH, and this conformational switch appeared to correspond to a change in the Lys73 protonation state at low pH. In conjunction with computational analyses, our structures suggest that Lys73 has a perturbed acid dissociation constant (pKa) compared with acyl-enzyme complexes with β-lactams, hindering its function to deprotonate Glu166 and the initiation of the deacylation reaction. Further NMR analysis demonstrated Lys73 pKa to be ∼5.2 to 5.6. Together with previous ultrahigh-resolution crystal structures, these findings enable us to follow the proton transfer process of the entire acylation reaction and reveal the critical role of Lys73. They also shed light on the stability and reversibility of the avibactam carbamoyl acyl-enzyme complex, highlighting the effect of substrate functional groups in influencing the protonation states of catalytic residues and subsequently the progression of the reaction.
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Abstract
Quantum mechanics (QM) methods provide a fine description of receptor-ligand interactions and of chemical reactions. Their use in drug design and drug discovery is increasing, especially for complex systems including metal ions in the binding sites, for the design of highly selective inhibitors, for the optimization of bi-specific compounds, to understand enzymatic reactions, and for the study of covalent ligands and prodrugs. They are also used for generating molecular descriptors for predictive QSAR/QSPR models and for the parameterization of force fields. Thanks to the continuous increase of computational power offered by GPUs and to the development of sophisticated algorithms, QM methods are becoming part of the standard tools used in computer-aided drug design (CADD). We present the most used QM methods and software packages, and we discuss recent representative applications in drug design and drug discovery.
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Affiliation(s)
- Martin Kotev
- Global Research Informatics/Cheminformatics and Drug Design, Evotec (France) SAS, Toulouse, France
| | - Laurie Sarrat
- Global Research Informatics/Cheminformatics and Drug Design, Evotec (France) SAS, Toulouse, France
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5
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Kim S, Kaliszewski CM, Guidez EB, Gordon MS. Benchmarking the Effective Fragment Potential Dispersion Correction on the S22 Test Set. J Phys Chem A 2018; 122:4076-4084. [PMID: 29601202 DOI: 10.1021/acs.jpca.7b11628] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The usual modeling of dispersion interactions in density functional theory (DFT) is often limited by the use of empirically fitted parameters. In this study, the accuracies of the popular empirical dispersion corrections and the first-principles derived effective fragment potential (EFP) dispersion correction are compared by computing the DFT-D and HF-D equilibria interaction energies and intermolecular distances of the S22 test set dimers. Functionals based on the local density approximation (LDA) and generalized gradient approximation (GGA), as well as hybrid functionals, are compared for the DFT-D calculations using coupled cluster CCSD(T) at the complete basis set (CBS) limit as the reference method. In general, the HF-D(EFP) method provides accurate equilibrium dimerization energies and intermolecular distances for hydrogen-bonded systems compared to the CCSD(T)/CBS reference data without using any empirical parameters. For dispersion-dominant and mixed systems, the structures and interaction energies obtained with the B3LYP-D(EFP) method are similar to or better than those obtained with the other DFT-D and HF-D methods. Overall, the first-principles derived -D(EFP) correction presents a robust alternative to the empirical -D corrections when used with the B3LYP functional for dispersion-dominant and mixed systems or with Hartree-Fock for hydrogen-bonded systems.
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Affiliation(s)
| | | | - Emilie B Guidez
- Department of Chemistry , University of Colorado Denver , Denver , Colorado 80217 , United States
| | - Mark S Gordon
- Department of Chemistry and Ames Laboratory USDOE , Iowa State University , Ames , Iowa 50011 , United States
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6
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Elucidating a chemical defense mechanism of Antarctic sponges: A computational study. J Mol Graph Model 2016; 71:104-115. [PMID: 27894019 DOI: 10.1016/j.jmgm.2016.11.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/21/2016] [Accepted: 11/06/2016] [Indexed: 11/22/2022]
Abstract
In 2000, a novel secondary metabolite (erebusinone, Ereb) was isolated from the Antarctic sea sponge, Isodictya erinacea. The bioactivity of Ereb was investigated, and it was found to inhibit molting when fed to the arthropod species Orchomene plebs. Xanthurenic acid (XA) is a known endogenous molt regulator present in arthropods. Experimental studies have confirmed that XA inhibits molting by binding to either (or both) of two P450 enzymes (CYP315a1 or CYP314a1) that are responsible for the final two hydroxylations in the production of the molt-inducing hormone, 20-hydroxyecdysone (20E). The lack of crystal structures and biochemical assays for CYP315a1 or CYP314a1, has prevented further experimental exploration of XA and Ereb's molt inhibition mechanisms. Herein, a wide array of computational techniques - homology modeling, molecular dynamics simulations, binding site bioinformatics, flexible receptor-flexible ligand docking, and molecular mechanics-generalized Born surface area calculations - have been employed to elucidate the structure-function relationships between the aforementioned P450s and the two described small molecule inhibitors (Ereb and XA). Results indicate that Ereb likely targets CYP315a1 by interacting with a network of aromatic residues in the binding site, while XA may inhibit both CYP315a1 and CYP314a1 because of its aromatic, as well as charged nature.
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7
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White JK, Handa S, Vankayala SL, Merkler DJ, Woodcock HL. Thiamin Diphosphate Activation in 1-Deoxy-d-xylulose 5-Phosphate Synthase: Insights into the Mechanism and Underlying Intermolecular Interactions. J Phys Chem B 2016; 120:9922-34. [PMID: 27537621 PMCID: PMC5379999 DOI: 10.1021/acs.jpcb.6b07248] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
1-Deoxy-d-xylulose 5-phosphate synthase (DXS) is a thiamin diphosphate (TDP) dependent enzyme that marks the beginning of the methylerythritol 4-phosphate isoprenoid biosynthesis pathway. The mechanism of action for DXS is still poorly understood and begins with the formation of a thiazolium ylide. This TDP activation step is thought to proceed through an intramolecular deprotonation by the 4'-aminopyrimidine ring of TDP; however, this step would occur only after an initial deprotonation of its own 4'-amino group. The mechanism of the initial deprotonation has been hypothesized, by analogy to transketolases, to occur via a histidine or an active site water molecule. Results from hybrid quantum mechanical/molecular mechanical (QM/MM) reaction path calculations reveal an ∼10 kcal/mol difference in transition state energies, favoring a water mediated mechanism over direct deprotonation by histidine. This difference was determined to be largely governed by electrostatic changes induced by conformational variations in the active site. Additionally, mutagenesis studies reveal DXS to be an evolutionarily resilient enzyme. Particularly, we hypothesize that residues H82 and H304 may act in a compensatory fashion if the other is lost due to mutation. Further, nucleus-independent chemical shifts (NICSs) and aromatic stabilization energy (ASE) calculations suggest that reduction in TDP aromaticity also serves as a factor for regulating ylide formation and controlling reactivity.
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Affiliation(s)
- Justin K. White
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
| | - Sumit Handa
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0332, United States
| | - Sai Lakshmana Vankayala
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
| | - David J. Merkler
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
| | - H. Lee Woodcock
- Department of Chemistry, University of South Florida, 4202 E. Fowler Avenue, CHE205, Tampa, Florida 33620-5250, United States
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8
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Mhashilkar AS, Vankayala SL, Liu C, Kearns F, Mehrotra P, Tzertzinis G, Palli SR, Woodcock HL, Unnasch TR. Identification of Ecdysone Hormone Receptor Agonists as a Therapeutic Approach for Treating Filarial Infections. PLoS Negl Trop Dis 2016; 10:e0004772. [PMID: 27300294 PMCID: PMC4907521 DOI: 10.1371/journal.pntd.0004772] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 05/21/2016] [Indexed: 11/27/2022] Open
Abstract
Background A homologue of the ecdysone receptor has previously been identified in human filarial parasites. As the ecdysone receptor is not found in vertebrates, it and the regulatory pathways it controls represent attractive potential chemotherapeutic targets. Methodology/ Principal Findings Administration of 20-hydroxyecdysone to gerbils infected with B. malayi infective larvae disrupted their development to adult stage parasites. A stable mammalian cell line was created incorporating the B. malayi ecdysone receptor ligand-binding domain, its heterodimer partner and a secreted luciferase reporter in HEK293 cells. This was employed to screen a series of ecdysone agonist, identifying seven agonists active at sub-micromolar concentrations. A B. malayi ecdysone receptor ligand-binding domain was developed and used to study the ligand-receptor interactions of these agonists. An excellent correlation between the virtual screening results and the screening assay was observed. Based on both of these approaches, steroidal ecdysone agonists and the diacylhydrazine family of compounds were identified as a fruitful source of potential receptor agonists. In further confirmation of the modeling and screening results, Ponasterone A and Muristerone A, two compounds predicted to be strong ecdysone agonists stimulated expulsion of microfilaria and immature stages from adult parasites. Conclusions The studies validate the potential of the B. malayi ecdysone receptor as a drug target and provide a means to rapidly evaluate compounds for development of a new class of drugs against the human filarial parasites. The human filarial parasites are the causative agents of two neglected tropical diseases targeted for elimination by the international community. The current elimination programs rely upon the mass distribution of a limited number of drugs, leaving the programs open to failure in the event that resistance develops. Thus, there is a critical need for novel chemotherapeutic agents to supplement the current arsenal. The filarial parasites are ecdysozoans, whose developmental processes are controlled by a master regulator, the ecdysone receptor. Here we validate the potential of the filarial ecdysone receptor as a chemotherapeutic target and report the development of high throughput and virtual screening assays that may be used to compounds that target it.
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Affiliation(s)
- Amruta S. Mhashilkar
- Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Sai L. Vankayala
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Canhui Liu
- Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
| | - Fiona Kearns
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Priyanka Mehrotra
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - George Tzertzinis
- New England Biolabs, Ipswich, Massachusetts, United States of America
| | - Subba R. Palli
- Department of Entomology, University of Kentucky, Lexington, Kentucky, United States of America
| | - H. Lee Woodcock
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
| | - Thomas R. Unnasch
- Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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9
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In Silico Characterization of the Binding Affinity of Dendrimers to Penicillin-Binding Proteins (PBPs): Can PBPs be Potential Targets for Antibacterial Dendrimers? Appl Biochem Biotechnol 2016; 178:1546-66. [DOI: 10.1007/s12010-015-1967-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 12/22/2015] [Indexed: 10/22/2022]
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10
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Structural and computational analysis of peptide recognition mechanism of class-C type penicillin binding protein, alkaline D-peptidase from Bacillus cereus DF4-B. Sci Rep 2015; 5:13836. [PMID: 26370172 PMCID: PMC4570186 DOI: 10.1038/srep13836] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 08/07/2015] [Indexed: 01/07/2023] Open
Abstract
Alkaline D-peptidase from Bacillus cereus DF4-B, called ADP, is a D-stereospecific endopeptidase reacting with oligopeptides containing D-phenylalanine (D-Phe) at N-terminal penultimate residue. ADP has attracted increasing attention because it is useful as a catalyst for synthesis of D-Phe oligopeptides or, with the help of substrate mimetics, L-amino acid peptides and proteins. Structure and functional analysis of ADP is expected to elucidate molecular mechanism of ADP. In this study, the crystal structure of ADP (apo) form was determined at 2.1 Å resolution. The fold of ADP is similar to that of the class C penicillin-binding proteins of type-AmpH. Docking simulations and fragment molecular orbital analyses of two peptides, (D-Phe)4 and (D-Phe)2-(L-Phe)2, with the putative substrate binding sites of ADP indicated that the P1 residue of the peptide interacts with hydrophobic residues at the S1 site of ADP. Furthermore, molecular dynamics simulation of ADP for 50 nsec suggested that the ADP forms large cavity at the active site. Formation of the cavity suggested that the ADP has open state in the solution. For the ADP, having the open state is convenient to bind the peptides having bulky side chain, such as (D-Phe)4. Taken together, we predicted peptide recognition mechanism of ADP.
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11
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Antioxidant Properties of Kanakugiol Revealed Through the Hydrogen Atom Transfer, Electron Transfer and M2+ (M2+ = Cu(II) or Co(II) Ion) Coordination Ability Mechanisms. A DFT Study In Vacuo and in Solution. FOOD BIOPHYS 2015. [DOI: 10.1007/s11483-015-9397-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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12
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Goerigk L, Collyer CA, Reimers JR. Recommending Hartree–Fock Theory with London-Dispersion and Basis-Set-Superposition Corrections for the Optimization or Quantum Refinement of Protein Structures. J Phys Chem B 2014; 118:14612-26. [DOI: 10.1021/jp510148h] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Lars Goerigk
- School
of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Charles A. Collyer
- School
of Molecular Bioscience, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Jeffrey R. Reimers
- Centre
for Quantum and Molecular Structure, College of Sciences, Shanghai University, Shanghai 200444, China
- School
of Physics and Advanced Materials, The University of Technology, Sydney, New South Wales 2007, Australia
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13
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Hargis JC, White JK, Chen Y, Woodcock HL. Can molecular dynamics and QM/MM solve the penicillin binding protein protonation puzzle? J Chem Inf Model 2014; 54:1412-24. [PMID: 24697903 PMCID: PMC4036751 DOI: 10.1021/ci5000517] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
![]()
Benzylpenicillin, a member of the
β-lactam antibiotic class, has been widely used to combat bacterial
infections since 1947. The general mechanism is well-known: a serine
protease enzyme (i.e., DD-peptidase) forms a long lasting intermediate
with the lactam ring of the antibiotic known as acylation, effectively
preventing biosynthesis of the bacterial cell wall. Despite this overall
mechanistic understanding, many details of binding and catalysis are
unclear. Specifically, there is ongoing debate about active site protonation
states and the role of general acids/bases in the reaction. Herein,
a unique combination of MD simulations, QM/MM minimizations, and QM/MM
orbital analyses is combined with systematic variation of active site
residue protonation states. Critical interactions that maximize the
stability of the bound inhibitor are examined and used as metrics.
This approach was validated by examining cefoxitin interactions in
the CTX-M β-lactamase from E. coli and compared to an ultra high-resolution (0.88 Å) crystal structure.
Upon confirming the approach used, an investigation of the preacylated Streptomyces R61 active site with bound benzylpenicillin
was performed, varying the protonation states of His298 and Lys65.
We concluded that protonated His298 and deprotonated Lys65 are most
likely to exist in the R61 active site.
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Affiliation(s)
- Jacqueline C Hargis
- Department of Chemistry, University of South Florida , Tampa, Florida 33620, United States
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