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Reddy N, Girdhari L, Shungube M, Gouws AC, Peters BK, Rajbongshi KK, Baijnath S, Mdanda S, Ntombela T, Arumugam T, Bester LA, Singh SD, Chuturgoon A, Arvidsson PI, Maguire GEM, Kruger HG, Govender T, Naicker T. Neutralizing Carbapenem Resistance by Co-Administering Meropenem with Novel β-Lactam-Metallo-β-Lactamase Inhibitors. Antibiotics (Basel) 2023; 12:antibiotics12040633. [PMID: 37106995 PMCID: PMC10135050 DOI: 10.3390/antibiotics12040633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2023] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 04/29/2023] Open
Abstract
Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an urgent global need for clinical metallo-β-lactamase inhibitors (MBLIs) has become dire. To address this problem, this study evaluated BP2, a novel beta-lactam-derived β-lactamase inhibitor, co-administered with meropenem. According to the antimicrobial susceptibility results, BP2 potentiates the synergistic activity of meropenem to a minimum inhibitory concentration (MIC) of ≤1 mg/L. In addition, BP2 is bactericidal over 24 h and safe to administer at the selected concentrations. Enzyme inhibition kinetics showed that BP2 had an apparent inhibitory constant (Kiapp) of 35.3 µM and 30.9 µM against New Delhi Metallo-β-lactamase (NDM-1) and Verona Integron-encoded Metallo-β-lactamase (VIM-2), respectively. BP2 did not interact with glyoxylase II enzyme up to 500 µM, indicating specific (MBL) binding. In a murine infection model, BP2 co-administered with meropenem was efficacious, observed by the >3 log10 reduction in K. pneumoniae NDM cfu/thigh. Given the promising pre-clinical results, BP2 is a suitable candidate for further research and development as an (MBLI).
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Peters BK, Reddy N, Shungube M, Girdhari L, Baijnath S, Mdanda S, Chetty L, Ntombela T, Arumugam T, Bester LA, Singh SD, Chuturgoon A, Arvidsson PI, Maguire GEM, Kruger HG, Naicker T, Govender T. In Vitro and In Vivo Development of a β-Lactam-Metallo-β-Lactamase Inhibitor: Targeting Carbapenem-Resistant Enterobacterales. ACS Infect Dis 2023; 9:486-496. [PMID: 36786013 PMCID: PMC10012271 DOI: 10.1021/acsinfecdis.2c00485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
β-lactams are the most prescribed class of antibiotics due to their potent, broad-spectrum antimicrobial activities. However, alarming rates of antimicrobial resistance now threaten the clinical relevance of these drugs, especially for the carbapenem-resistant Enterobacterales expressing metallo-β-lactamases (MBLs). Antimicrobial agents that specifically target these enzymes to restore the efficacy of last resort β-lactam drugs, that is, carbapenems, are therefore desperately needed. Herein, we present a cyclic zinc chelator covalently attached to a β-lactam scaffold (cephalosporin), that is, BP1. Observations from in vitro assays (with seven MBL expressing bacteria from different geographies) have indicated that BP1 restored the efficacy of meropenem to ≤ 0.5 mg/L, with sterilizing activity occurring from 8 h postinoculation. Furthermore, BP1 was nontoxic against human hepatocarcinoma cells (IC50 > 1000 mg/L) and exhibited a potency of (Kiapp) 24.8 and 97.4 μM against Verona integron-encoded MBL (VIM-2) and New Delhi metallo β-lactamase (NDM-1), respectively. There was no inhibition observed from BP1 with the human zinc-containing enzyme glyoxylase II up to 500 μM. Preliminary molecular docking of BP1 with NDM-1 and VIM-2 sheds light on BP1's mode of action. In Klebsiella pneumoniae NDM infected mice, BP1 coadministered with meropenem was efficacious in reducing the bacterial load by >3 log10 units' postinfection. The findings herein propose a favorable therapeutic combination strategy that restores the activity of the carbapenem antibiotic class and complements the few MBL inhibitors under development, with the ultimate goal of curbing antimicrobial resistance.
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Sabe VT, Ntombela T, Jhamba LA, Maguire GEM, Govender T, Naicker T, Kruger HG. Current trends in computer aided drug design and a highlight of drugs discovered via computational techniques: A review. Eur J Med Chem 2021; 224:113705. [PMID: 34303871 DOI: 10.1016/j.ejmech.2021.113705] [Citation(s) in RCA: 160] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 07/12/2021] [Accepted: 07/12/2021] [Indexed: 12/30/2022]
Abstract
Computer-aided drug design (CADD) is one of the pivotal approaches to contemporary pre-clinical drug discovery, and various computational techniques and software programs are typically used in combination, in a bid to achieve the desired outcome. Several approved drugs have been developed with the aid of CADD. On SciFinder®, we evaluated more than 600 publications through systematic searching and refining, using the terms, virtual screening; software methods; computational studies and publication year, in order to obtain data concerning particular aspects of CADD. The primary focus of this review was on the databases screened, virtual screening and/or molecular docking software program used. Furthermore, we evaluated the studies that subsequently performed molecular dynamics (MD) simulations and we reviewed the software programs applied, the application of density functional theory (DFT) calculations and experimental assays. To represent the latest trends, the most recent data obtained was between 2015 and 2020, consequently the most frequently employed techniques and software programs were recorded. Among these, the ZINC database was the most widely preferred with an average use of 31.2%. Structure-based virtual screening (SBVS) was the most prominently used type of virtual screening and it accounted for an average of 57.6%, with AutoDock being the preferred virtual screening/molecular docking program with 41.8% usage. Following the screening process, 38.5% of the studies performed MD simulations to complement the virtual screening and GROMACS with 39.3% usage, was the popular MD software program. Among the computational techniques, DFT was the least applied whereby it only accounts for 0.02% average use. An average of 36.5% of the studies included reports on experimental evaluations following virtual screening. Ultimately, since the inception and application of CADD in pre-clinical drug discovery, more than 70 approved drugs have been discovered, and this number is steadily increasing over time.
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Ani FE, Ibeji CU, Obasi NL, Kelani MT, Ukogu K, Tolufashe GF, Ogundare SA, Oyeneyin OE, Maguire GEM, Kruger HG. Crystal, spectroscopic and quantum mechanics studies of Schiff bases derived from 4-nitrocinnamaldehyde. Sci Rep 2021; 11:8151. [PMID: 33854091 PMCID: PMC8046777 DOI: 10.1038/s41598-021-87370-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 03/26/2021] [Indexed: 02/02/2023] Open
Abstract
Two Schiff bases, (E)-1-(4-methoxyphenyl)-N-((E)-3-(4-nitrophenyl)allylidene)methanamine (compound 1) and (E)-N-((E)-3-(4-nitrophenyl)allylidene)-2-phenylethanamine (compound 2) have been synthesized and characterized using spectroscopic methods; time of flight MS, 1H and 13C NMR, FT-IR, UV-VIS, photoluminescence and crystallographic methods. The structural and electronic properties of compounds 1 and 2 in the ground state were also examined using the DFT/B3LYP functional and 6-31 + G(d,p) basis set, while the electronic transitions for excited state calculations were carried out using the TD-DFT/6-31 + G(d,p) method. The Schiff base compounds, 1 and 2 crystallized in a monoclinic crystal system and the P21/c space group. The emission spectra of the compounds are attributed to conjugated π-bond interaction while the influence of the intra-ligand charge transfer resulted in a broad shoulder for 1 and a double emission peak for 2. The calculated transitions at 450 and 369 nm for 1 and 2 respectively are in reasonable agreement with the experimental results. The higher values of dipole moment, linear polarizability and first hyperpolarizability of 1, suggest a better optical property and better candidate for the development of nonlinear optical (NLO) materials.
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Ntombela T, Seupersad A, Maseko S, Ibeji CU, Tolufashe G, Maphumulo SI, Naicker T, Baijnath S, Maguire GEM, Govender T, Lamichhane G, Honarparvar B, Kruger HG. Mechanistic insight on the inhibition of D, D-carboxypeptidase from Mycobacterium tuberculosis by β-lactam antibiotics: an ONIOM acylation study. J Biomol Struct Dyn 2021; 40:7645-7655. [PMID: 33719919 DOI: 10.1080/07391102.2021.1899052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Mycobacterium tuberculosis cell wall is intricate and impermeable to many agents. A D, D-carboxypeptidase (DacB1) is one of the enzymes involved in the biosynthesis of cell wall peptidoglycan and catalyzes the terminal D-alanine cleavage from pentapeptide precursors. Catalytic activity and mechanism by which DacB1 functions is poorly understood. Herein, we investigated the acylation mechanism of DacB1 by β-lactams using a 6-membered ring transition state model that involves a catalytic water molecule in the reaction pathway. The full transition states (TS) optimization plus frequency were achieved using the ONIOM (B3LYP/6-31 + G(d): AMBER) method. Subsequently, the activation free energies were computed via single-point calculations on fully optimized structures using B3LYP/6-311++(d,p): AMBER and M06-2X/6-311++(d,p): AMBER with an electronic embedding scheme. The 6-membered ring transition state is an effective model to examine the inactivation of DacB1 via acylation by β-lactams antibiotics (imipenem, meropenem, and faropenem) in the presence of the catalytic water. The ΔG# values obtained suggest that the nucleophilic attack on the carbonyl carbon is the rate-limiting step with 13.62, 19.60 and 30.29 kcal mol-1 for Imi-DacB1, Mero-DacB1 and Faro-DacB1, respectively. The electrostatic potential (ESP) and natural bond orbital (NBO) analysis provided significant electronic details of the electron-rich region and charge delocalization, respectively, based on the concerted 6-membered ring transition state. The stabilization energies of charge transfer within the catalytic reaction pathway concurred with the obtained activation free energies. The outcomes of this study provide important molecular insight into the inactivation of D, D-carboxypeptidase by β-lactams.
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Sanusi ZK, Lawal MM, Gupta PL, Govender T, Baijnath S, Naicker T, Maguire GEM, Honarparvar B, Roitberg AE, Kruger HG. Exploring the concerted mechanistic pathway for HIV-1 PR-substrate revealed by umbrella sampling simulation. J Biomol Struct Dyn 2020; 40:1736-1747. [PMID: 33073714 DOI: 10.1080/07391102.2020.1832578] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
HIV-1 protease (HIV-1 PR) is an essential enzyme for the replication process of its virus, and therefore considered an important target for the development of drugs against the acquired immunodeficiency syndrome (AIDS). Our previous study shows that the catalytic mechanism of subtype B/C-SA HIV-1 PR follows a one-step concerted acyclic hydrolysis reaction process using a two-layered ONIOM B3LYP/6-31++G(d,p) method. This present work is aimed at exploring the proposed mechanism of the proteolysis catalyzed by HIV-1 PR and to ensure our proposed mechanism is not an artefact of a single theoretical technique. Hence, we present umbrella sampling method that is suitable for calculating potential mean force (PMF) for non-covalent ligand/substrate-enzyme association/dissociation interactions which provide thermodynamic details for molecular recognition. The free activation energy results were computed in terms of PMF analysis within the hybrid QM(DFTB)/MM approach. The theoretical findings suggest that the proposed mechanism corresponds in principle with experimental data. Given our observations, we suggest that the QM/MM MD method can be used as a reliable computational technique to rationalize lead compounds against specific targets such as the HIV-1 protease.
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Mhlongo NZ, Ebenhan T, Driver CHS, Maguire GEM, Kruger HG, Govender T, Naicker T. Microwave-assisted synthesis of meso-carboxyalkyl-BODIPYs and an application to fluorescence imaging. Org Biomol Chem 2020; 18:7876-7883. [PMID: 32986056 DOI: 10.1039/d0ob01415j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this study, a significantly improved method for the synthesis of modular meso-BODIPY (boron dipyrromethene) derivatives possessing a free carboxylic acid group (which was subsequently coupled to peptides), is disclosed. This method provides a vastly efficient synthetic route with a > threefold higher overall yield than other reports. The resultant meso-BODIPY acid allowed for further easy incorporation into peptides. The meso-BODIPY peptides showed absorption maxima from 495-498 nm and emission maxima from 504-506 nm, molar absorptivity coefficients from 33 383-80 434 M-1 cm-1 and fluorescent quantum yields from 0.508-0.849. The meso-BODIPY-c(RGDyK) peptide was evaluated for plasma stability and (proved to be durable even up to 4 h) was then assessed for its fluorescence imaging applicability in vivo and ex vivo. The optical imaging in vivo was limited due to autofluorescence, however, the ex vivo tissue analysis displayed BODIPY-c(RGDyK) internalization and cancer detection thereby making it a novel tumor-integrin associated fluorescent probe while displaying the lack of interference the dye has on the properties of this ligand to bind the receptor.
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Tolufashe GF, Sabe VT, Ibeji CU, Ntombela T, Govender T, Maguire GEM, Kruger HG, Lamichhane G, Honarparvar B. Structure and Function of L,D- and D,D-Transpeptidase Family Enzymes from Mycobacterium tuberculosis. Curr Med Chem 2020; 27:3250-3267. [PMID: 30501595 DOI: 10.2174/0929867326666181203150231] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 09/28/2018] [Accepted: 11/22/2018] [Indexed: 01/21/2023]
Abstract
Peptidoglycan, the exoskeleton of bacterial cell and an essential barrier that protects the cell, is synthesized by a pathway where the final steps are catalysed by transpeptidases. Knowledge of the structure and function of these vital enzymes that generate this macromolecule in M. tuberculosis could facilitate the development of potent lead compounds against tuberculosis. This review summarizes the experimental and computational studies to date on these aspects of transpeptidases in M. tuberculosis that have been identified and validated. The reported structures of L,D- and D,D-transpeptidases, as well as their functionalities, are reviewed and the proposed enzymatic mechanisms for L,D-transpeptidases are summarized. In addition, we provide bioactivities of known tuberculosis drugs against these enzymes based on both experimental and computational approaches. Advancing knowledge about these prominent targets supports the development of new drugs with novel inhibition mechanisms overcoming the current need for new drugs against tuberculosis.
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Sanusi ZK, Lawal MM, Govender T, Baijnath S, Naicker T, Maguire GEM, Honarparvar B, Kruger HG. Concerted hydrolysis mechanism of HIV-1 natural substrate against subtypes B and C-SA PR: insight through molecular dynamics and hybrid QM/MM studies. Phys Chem Chem Phys 2020; 22:2530-2539. [PMID: 31942584 DOI: 10.1039/c9cp05639d] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
It is well known that understanding the catalytic mechanism of HIV-1 PR is the rationale on which its inhibitors were developed; therefore, a better understanding of the mechanism of natural substrate hydrolysis is important. Herein, the reaction mechanism of HIV-1 natural substrates with subtypes B and common mutant in South Africa (subtype C-SA) protease were studied through transition state modelling, using a general acid-general base (GA-GB) one-step concerted process. The activation free energies of enzyme-substrate complexes were compared based on their rate of hydrolysis using a two-layered ONIOM (B3LYP/6-31++G(d,p):AMBER) method. We expanded our computational model to obtain a better understanding of the mechanism of hydrolysis as well as how the enzyme recognises or chooses the cleavage site of the scissile bonds. Using this model, a potential substrate-based inhibitor could be developed with better potency. The calculated activation energies of natural substrates in our previous study correlated well with experimental data. A similar trend was observed for the Gag and Gag-Pol natural substrates in the present work for both enzyme complexes except for the PR-RT substrate. Natural bond orbital (NBO) analysis was also applied to determine the extent of charge transfer within the QM part of both enzymes considered and the PR-RT natural substrate. The result of this study shows that the method can be utilized as a dependable computational technique to rationalize lead compounds against specific targets.
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Sabe VT, Tolufashe GF, Ibeji CU, Maseko SB, Govender T, Maguire GEM, Lamichhane G, Honarparvar B, Kruger HG. Identification of potent L,D-transpeptidase 5 inhibitors for Mycobacterium tuberculosis as potential anti-TB leads: virtual screening and molecular dynamics simulations. J Mol Model 2019; 25:328. [PMID: 31656981 DOI: 10.1007/s00894-019-4196-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 08/28/2019] [Indexed: 11/26/2022]
Abstract
Virtual screening is a useful in silico approach to identify potential leads against various targets. It is known that carbapenems (doripenem and faropenem) do not show any reasonable inhibitory activities against L,D-transpeptidase 5 (LdtMt5) and also an adduct of meropenem exhibited slow acylation. Since these drugs are active against L,D-transpeptidase 2 (LdtMt2), understanding the differences between these two enzymes is essential. In this study, a ligand-based virtual screening of 12,766 compounds followed by molecular dynamics (MD) simulations was applied to identify potential leads against LdtMt5. To further validate the obtained virtual screening ranking for LdtMt5, we screened the same libraries of compounds against LdtMt2 which had more experimetal and calculated binding energies reported. The observed consistency between the binding affinities of LdtMt2 validates the obtained virtual screening binding scores for LdtMt5. We subjected 37 compounds with docking scores ranging from - 7.2 to - 9.9 kcal mol-1 obtained from virtual screening for further MD analysis. A set of compounds (n = 12) from four antibiotic classes with ≤ - 30 kcal mol-1 molecular mechanics/generalized born surface area (MM-GBSA) binding free energies (ΔGbind) was characterized. A final set of that, all β-lactams (n = 4), was considered. The outcome of this study provides insight into the design of potential novel leads for LdtMt5. Graphical abstract.
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Sanusi ZK, Lawal MM, Govender T, Maguire GEM, Honarparvar B, Kruger HG. Theoretical Model for HIV-1 PR That Accounts for Substrate Recognition and Preferential Cleavage of Natural Substrates. J Phys Chem B 2019; 123:6389-6400. [DOI: 10.1021/acs.jpcb.9b02207] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Ibeji CU, Lawal MM, Tolufashe GF, Govender T, Naicker T, Maguire GEM, Lamichhane G, Kruger HG, Honarparvar B. The Driving Force for the Acylation of β-Lactam Antibiotics by L,D-Transpeptidase 2: Quantum Mechanics/Molecular Mechanics (QM/MM) Study. Chemphyschem 2019; 20:1126-1134. [PMID: 30969480 DOI: 10.1002/cphc.201900173] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 03/13/2019] [Indexed: 11/06/2022]
Abstract
β-lactam antibiotics, which are used to treat infectious diseases, are currently the most widely used class of antibiotics. This study focused on the chemical reactivity of five- and six-membered ring systems attached to the β-lactam ring. The ring strain energy (RSE), force constant (FC) of amide (C-N), acylation transition states and second-order perturbation stabilization energies of 13 basic structural units of β-lactam derivatives were computed using the M06-2X and G3/B3LYP multistep method. In the ring strain calculations, an isodesmic reaction scheme was used to obtain the total energies. RSE is relatively greater in the five-(1a-2c) compared to the six-membered ring systems except for 4b, which gives a RSE that is comparable to five-membered ring lactams. These variations were also observed in the calculated inter-atomic amide bond distances (C-N), which is why the six-membered ring lactams C-N bond are more rigid than those with five-membered ring lactams. The calculated ΔG# values from the acylation reaction of the lactams (involving the S-H group of the cysteine active residue from L,D transpeptidase 2) revealed a faster rate of C-N cleavage in the five-membered ring lactams especially in the 1-2 derivatives (17.58 kcal mol-1 ). This observation is also reflected in the calculated amide bond force constant (1.26 mDyn/A) indicating a weaker bond strength, suggesting that electronic factors (electron delocalization) play more of a role on reactivity of the β-lactam ring, than ring strain.
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Maseko SB, Govender D, Govender T, Naicker T, Lin J, Maguire GEM, Kruger HG. Optimized Procedure for Recovering HIV-1 Protease (C-SA) from Inclusion Bodies. Protein J 2019; 38:30-36. [PMID: 30666487 DOI: 10.1007/s10930-018-9805-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
HIV-1 is an infectious virus that causes acquired immunodeficiency syndrome (AIDS) and it is one of the major causes of deaths worldwide. The production of HIV-1 protease (PR) on a large scale has been a problem for scientists due to its cytotoxicity, low yield, insolubility, and low activity. HIV-1 C-SA protease has been cloned, expressed, and purified previously, however, with low recovery (0.25 mg/L). Herein we report an optimal expression and solubilisation procedure to recover active HIV-1 C-SA protease enzyme from inclusion bodies. The HIV protease was expressed in seven different vectors (pET11b, pET15b, pET28a pET32a, pET39b, pET41b and pGEX 6P-1). The highest expression was achieved when the vector pET32a (Trx tag) was employed. A total of 19.5 mg of fusion protein was refolded of which 5.5 mg of active protease was obtained after cleavage. The free protease had a high specific activity of 2.81 µmoles/min/mg. Interestingly the Trx-fusion protein also showed activity closer (1.24 µmoles/min/mg) to that of the free protease suggesting that the pET32a vector (Trx tag) expressed in BL21(DE3) pLysS provides a more efficient way to obtain HIV-1 protease.
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Tolufashe GF, Halder AK, Ibeji CU, Lawal MM, Ntombela T, Govender T, Maguire GEM, Lamichhane G, Kruger HG, Honarparvar B. Inhibition of Mycobacterium tuberculosis
L,D-Transpeptidase 5 by Carbapenems: MD and QM/MM Mechanistic Studies. ChemistrySelect 2018. [DOI: 10.1002/slct.201803184] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Lawal MM, Sanusi ZK, Govender T, Tolufashe GF, Maguire GEM, Honarparvar B, Kruger HG. Unraveling the concerted catalytic mechanism of the human immunodeficiency virus type 1 (HIV-1) protease: a hybrid QM/MM study. Struct Chem 2018. [DOI: 10.1007/s11224-018-1251-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Ibeji CU, Tolufashe GF, Ntombela T, Govender T, Maguire GEM, Lamichhane G, Kruger HG, Honarparvar B. The catalytic role of water in the binding site of l,d-transpeptidase 2 within acylation mechanism: A QM/MM (ONIOM) modelling. Tuberculosis (Edinb) 2018; 113:222-230. [PMID: 30514506 DOI: 10.1016/j.tube.2018.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Revised: 10/11/2018] [Accepted: 10/14/2018] [Indexed: 01/13/2023]
Abstract
Mycobacterium tuberculosis is the causative agent of Tuberculosis. Formation of 3 → 3 crosslinks in the peptidoglycan layer of M. tuberculosis is catalyzed by l,d-transpeptidases. These enzymes can confer resistance against classical β-lactams that inhibit enzymes that generate 4 → 3 peptidoglycan crosslinks. The focus of this study is to investigate the catalytic role of water molecules in the acylation mechanism of the β-lactam ring within two models; 4- and 6-membered ring systems using two-layered our Own N-layer integrated Molecular Mechanics ONIOM (B3LYP/6-311++G(2d,2p): AMBER) model. The obtained thermochemical parameters revealed that the 6-membered ring model best describes the inhibition mechanism of acylation which indicates the role of water in the preference of 6-membered ring reaction pathway. This finding is in accordance with experimental data for the rate-limiting step of cysteine protease with the same class of inhibitor and binding affinity for both inhibitors. As expected, the ΔG# results also reveal that the 6-membered ring reaction pathway is the most favourable. The electrostatic potential (ESP) and the natural bond orbital analysis (NBO) showed stronger interactions in 6-membered ring transition state (TS-6) mechanism involving water in the active site of the enzyme. This study could be helpful in the development of novel antibiotics against l,d-transpeptidase.
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Maphumulo SI, Halder AK, Govender T, Maseko S, Maguire GEM, Honarparvar B, Kruger HG. Exploring the flap dynamics of the South African HIV subtype C protease in presence of FDA-approved inhibitors: MD study. Chem Biol Drug Des 2018; 92:1899-1913. [PMID: 30003668 DOI: 10.1111/cbdd.13364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Accepted: 07/09/2018] [Indexed: 01/01/2023]
Abstract
HIV-1 protease (HIV PR) is considered as one of the most attractive targets for the treatment of HIV and the impact of flap dynamics of HIV PR on the binding affinities of protease inhibitors (PIs) is a crucial ongoing research field. Recently, our research group evaluated the binding affinities of different FDA approved PIs against the South African HIV-1 subtype C (C-SA) protease (PR). The CSA-HIV PR displayed weaker binding affinity for most of the clinical PIs compared to HIV-1 B subtype for West and Central Europe, the Americas. In the current work, the flap dynamics of four different systems of HIV-1 C-SA PR complexed to FDA approved second generation PIs and its impact on binding was explored over the molecular dynamic trajectories. It was observed that the interactions of the selected drugs with the binding site residues of the protease may not be the major contributor for affinity towards PIs. Various post-MD analyses were performed, also entropic contributions, solvation free energies and hydrophobic core formation interactions were studied to assess how the flap dynamics of C-SA PR which is affected by such factors. From these contributions, large van der Waals interactions and low solvation free energies were found to be major factors for the higher activity of ATV against C-SA HIV PR. Furthermore, a comparatively stable hydrophobic core may be responsible for higher stability of the PR flaps of the ATV complex. The outcome of this study provides significant guidance to how the flap dynamics of C-SA PR is affected by various factors as a result of the binding affinity of various protease inhibitors. It will also assist with the design of potent inhibitors against C-SA HIV PR that apart from binding in the active site of PR can interacts with the flaps to prevent opening of the flaps resulting in inactivation of the protease.
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Thakar AS, Pansuriya PB, Friedrich HB, Maguire GEM. Crystal structure of methyl (1-phenylethyl)carbamate, C 10H 13NO 2. Z KRIST-NEW CRYST ST 2018. [DOI: 10.1515/ncrs-2017-0320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
C10H13NO2, monoclinic, P21 (no. 14), a = 9.9882(7) Å, b = 8.5202(6) Å, c = 23.1403(18) Å, β = 91.010(2)°, V = 1969.0(2) Å3, Z = 8, R
gt(F) = 0.0387, wR
ref(F
2) = 0.0919, T = 173(2)K.
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Ntombela T, Fakhar Z, Ibeji CU, Govender T, Maguire GEM, Lamichhane G, Kruger HG, Honarparvar B. Molecular insight on the non-covalent interactions between carbapenems and L,D-transpeptidase 2 from Mycobacterium tuberculosis: ONIOM study. J Comput Aided Mol Des 2018; 32:687-701. [PMID: 29845435 DOI: 10.1007/s10822-018-0121-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 05/14/2018] [Indexed: 12/01/2022]
Abstract
Tuberculosis remains a dreadful disease that has claimed many human lives worldwide and elimination of the causative agent Mycobacterium tuberculosis also remains elusive. Multidrug-resistant TB is rapidly increasing worldwide; therefore, there is an urgent need for improving the current antibiotics and novel drug targets to successfully curb the TB burden. L,D-Transpeptidase 2 is an essential protein in Mtb that is responsible for virulence and growth during the chronic stage of the disease. Both D,D- and L,D-transpeptidases are inhibited concurrently to eradicate the bacterium. It was recently discovered that classic penicillins only inhibit D,D-transpeptidases, while L,D-transpeptidases are blocked by carbapenems. This has contributed to drug resistance and persistence of tuberculosis. Herein, a hybrid two-layered ONIOM (B3LYP/6-31G+(d): AMBER) model was used to extensively investigate the binding interactions of LdtMt2 complexed with four carbapenems (biapenem, imipenem, meropenem, and tebipenem) to ascertain molecular insight of the drug-enzyme complexation event. In the studied complexes, the carbapenems together with catalytic triad active site residues of LdtMt2 (His187, Ser188 and Cys205) were treated at with QM [B3LYP/6-31+G(d)], while the remaining part of the complexes were treated at MM level (AMBER force field). The resulting Gibbs free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) for all complexes showed that the carbapenems exhibit reasonable binding interactions towards LdtMt2. Increasing the number of amino acid residues that form hydrogen bond interactions in the QM layer showed significant impact in binding interaction energy differences and the stabilities of the carbapenems inside the active pocket of LdtMt2. The theoretical binding free energies obtained in this study reflect the same trend of the experimental observations. The electrostatic, hydrogen bonding and Van der Waals interactions between the carbapenems and LdtMt2 were also assessed. To further examine the nature of intermolecular interactions for carbapenem-LdtMt2 complexes, AIM and NBO analysis were performed for the QM region (carbapenems and the active residues of LdtMt2) of the complexes. These analyses revealed that the hydrogen bond interactions and charge transfer from the bonding to anti-bonding orbitals between catalytic residues of the enzyme and selected ligands enhances the binding and stability of carbapenem-LdtMt2 complexes. The two-layered ONIOM (B3LYP/6-31+G(d): Amber) model was used to evaluate the efficacy of FDA approved carbapenems antibiotics towards LdtMt2.
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Sanusi ZK, Govender T, Maguire GEM, Maseko SB, Lin J, Kruger HG, Honarparvar B. An insight to the molecular interactions of the FDA approved HIV PR drugs against L38L↑N↑L PR mutant. J Comput Aided Mol Des 2018; 32:459-471. [PMID: 29397520 DOI: 10.1007/s10822-018-0099-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 01/16/2018] [Indexed: 01/12/2023]
Abstract
The aspartate protease of the human immune deficiency type-1 virus (HIV-1) has become a crucial antiviral target in which many useful antiretroviral inhibitors have been developed. However, it seems the emergence of new HIV-1 PR mutations enhances drug resistance, hence, the available FDA approved drugs show less activity towards the protease. A mutation and insertion designated L38L↑N↑L PR was recently reported from subtype of C-SA HIV-1. An integrated two-layered ONIOM (QM:MM) method was employed in this study to examine the binding affinities of the nine HIV PR inhibitors against this mutant. The computed binding free energies as well as experimental data revealed a reduced inhibitory activity towards the L38L↑N↑L PR in comparison with subtype C-SA HIV-1 PR. This observation suggests that the insertion and mutations significantly affect the binding affinities or characteristics of the HIV PIs and/or parent PR. The same trend for the computational binding free energies was observed for eight of the nine inhibitors with respect to the experimental binding free energies. The outcome of this study shows that ONIOM method can be used as a reliable computational approach to rationalize lead compounds against specific targets. The nature of the intermolecular interactions in terms of the host-guest hydrogen bond interactions is discussed using the atoms in molecules (AIM) analysis. Natural bond orbital analysis was also used to determine the extent of charge transfer between the QM region of the L38L↑N↑L PR enzyme and FDA approved drugs. AIM analysis showed that the interaction between the QM region of the L38L↑N↑L PR and FDA approved drugs are electrostatic dominant, the bond stability computed from the NBO analysis supports the results from the AIM application. Future studies will focus on the improvement of the computational model by considering explicit water molecules in the active pocket. We believe that this approach has the potential to provide information that will aid in the design of much improved HIV-1 PR antiviral drugs.
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Singh L, Kruger HG, Maguire GEM, Govender T, Parboosing R. Development and Evaluation of Peptide-Functionalized Gold Nanoparticles for HIV Integrase Inhibition. Int J Pept Res Ther 2018. [DOI: 10.1007/s10989-018-9673-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Maseko SB, Padayachee E, Govender T, Sayed Y, Kruger G, Maguire GEM, Lin J. I36T↑T mutation in South African subtype C (C-SA) HIV-1 protease significantly alters protease-drug interactions. Biol Chem 2017; 398:1109-1117. [PMID: 28525359 DOI: 10.1515/hsz-2017-0107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 05/04/2017] [Indexed: 12/31/2022]
Abstract
The efficacy of HIV-1 protease (PR) inhibition therapies is often compromised by the emergence of mutations in the PR molecule that reduces the binding affinity of inhibitors while maintaining viable catalytic activity and affinity for natural substrates. In the present study, we used a recombinant HIV-1 C-SA PR and a recently reported variant for inhibition (Ki, IC50) and thermodynamic studies against nine clinically used inhibitors. This is the first time that binding free energies for C-SA PR and the mutant are reported. This variant PR harbours a mutation and insertion (I36T↑T) at position 36 of the C-SA HIV-1 PR, and did not show a significant difference in the catalytic effect of the HIV-1 PR. However, the nine clinically approved HIV PR drugs used in this study demonstrated weaker inhibition and lower binding affinities toward the variant when compared to the wild type HIV-1 PR. All the protease inhibitors (PIs), except Amprenavir and Ritonavir exhibited a significant decrease in binding affinity (p<0.0001). Darunavir and Nelfinavir exhibited the weakest binding affinity, 155- and 95-fold decreases respectively, toward the variant. Vitality values for the variant PR, against the seven selected PIs, confirm the impact of the mutation and insertion on the South African HIV-1 subtype C PR. This information has important clinical implications for thousands of patients in Sub-Saharan Africa.
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Sanusi ZK, Govender T, Maguire GEM, Maseko SB, Lin J, Kruger HG, Honarparvar B. Investigation of the binding free energies of FDA approved drugs against subtype B and C-SA HIV PR: ONIOM approach. J Mol Graph Model 2017; 76:77-85. [PMID: 28711760 DOI: 10.1016/j.jmgm.2017.06.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 06/08/2017] [Accepted: 06/09/2017] [Indexed: 01/15/2023]
Abstract
Human immune virus subtype C is the most widely spread HIV subtype in Sub-Sahara Africa and South Africa. A profound structural insight on finding potential lead compounds is therefore necessary for drug discovery. The focus of this study is to rationalize the nine Food and Drugs Administration (FDA) HIV antiviral drugs complexed to subtype B and C-SA PR using ONIOM approach. To achieve this, an integrated two-layered ONIOM model was used to optimize the geometrics of the FDA approved HIV-1 PR inhibitors for subtype B. In our hybrid ONIOM model, the HIV-1 PR inhibitors as well as the ASP 25/25' catalytic active residues were treated at high level quantum mechanics (QM) theory using B3LYP/6-31G(d), and the remaining HIV PR residues were considered using the AMBER force field. The experimental binding energies of the PR inhibitors were compared to the ONIOM calculated results. The theoretical binding free energies (?Gbind) for subtype B follow a similar trend to the experimental results, with one exemption. The computational model was less suitable for C-SA PR. Analysis of the results provided valuable information about the shortcomings of this approach. Future studies will focus on the improvement of the computational model by considering explicit water molecules in the active pocket. We believe that this approach has the potential to provide much improved binding energies for complex enzyme drug interactions.
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Patel CR, Samipillai M, Friedrich HB, Kruger HG, Govender T, Maguire GEM. Crystal structure of 5,11,17,23-tetra( tert-butyl)-25,26,27,28-tetrahexoxycalix[4]arene, C 68H 104O 4. Z KRIST-NEW CRYST ST 2017. [DOI: 10.1515/ncrs-2016-0286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
C68H104O4, monoclinic, P21/n (no. 14), a = 19.4442(12) Å, b = 16.8522(11) Å, c = 38.048(3) Å, β = 92.400(1)°, V = 12456.4(14) Å3, Z = 8, R
gt(F) = 0.0488, wR
ref(F
2) = 0.1326, T = 153 K.
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Fakhar Z, Govender T, Maguire GEM, Lamichhane G, Walker RC, Kruger HG, Honarparvar B. Differential flap dynamics in l,d-transpeptidase2 from mycobacterium tuberculosis revealed by molecular dynamics. MOLECULAR BIOSYSTEMS 2017; 13:1223-1234. [PMID: 28480928 DOI: 10.1039/c7mb00110j] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Despite the advances in tuberculosis treatment, TB is still one the most deadly infectious diseases and remains a major global health quandary. Mycobacterium tuberculosis (Mtb) is the only known mycobacterium with a high content of 3→3 crosslinks in the biosynthesis of peptidoglycan, which is negligible in most bacterial species. An Mtb lacking LdtMt2 leads to alteration of the colony morphology and loss of virulence which makes this enzyme an attractive target. Regardless of the vital role of LdtMt2 for cell wall survival, the impact of ligand binding on the dynamics of the β-hairpin flap is still unknown. Understanding the structural and dynamical behaviour of the flap regions provides clear insight into the design of the effective inhibitors against LdtMt2. Carbapenems, an specific class of β-lactam family, have been shown to inactivate this enzyme. Herein a comprehensive investigation of the flap dynamics of LdtMt2 complex with substrate and three carbapenems namely, ertapenem, imipenem and meropenem is discussed and analyzed for the first account using 140 ns molecular dynamics simulations. The structural features (RMSD, RMSF and Rg) derived by MD trajectories were analyzed. Distance analysis, particularly tip-tip SER135-ASN167 index, identified conformational changes in terms of flap opening and closure within binding process. Principal component analysis (PCA) was employed to qualitatively understand the divergent effects of different inhibitors on the dominant motion of each residue. To probe different internal dynamics induced by ligand binding, dynamic cross-correlation marix (DCCM) analysis was used. The binding free energies of the selected complexes were assessed using MM-GBSA method and per residue free energy decomposition analysis were performed to characterize the contribution of the key residues to the total binding free energies.
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