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Rahman S, Iram S, Rehman MT, Hussain A, Jan AT, Kim J. Study of Amiloride Binding to Human Serum Albumin: Insights from Thermodynamic, Spectroscopic, and Molecular Docking Investigations. Molecules 2023; 28:7688. [PMID: 38067419 PMCID: PMC10707572 DOI: 10.3390/molecules28237688] [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: 10/10/2023] [Revised: 11/10/2023] [Accepted: 11/16/2023] [Indexed: 12/18/2023] Open
Abstract
This study was undertaken to investigate the interaction between the sodium channel blocker amiloride (AML) and human serum albumin (HSA). A combination of multi-spectroscopic techniques and computational methods were employed to identify the AML binding site on HSA and the forces responsible for the formation of the HSA-AML complex. Our findings revealed that AML specifically binds to Sudlow's site II, located in subdomain IIIA of HSA, and that the complex formed is stabilized using van der Waals hydrogen-bonding and hydrophobic interactions. FRET analysis showed that the distance between AML and Trp214 was optimal for efficient quenching. UV-Vis spectroscopy and circular dichroism indicated minor changes in the structure of HSA after AML binding, and molecular dynamics simulations (MDS) conducted over 100 ns provided additional evidence of stable HSA-AML-complex formation. This study enhances understanding of the interaction between AML and HSA and the mechanism responsible.
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Affiliation(s)
- Safikur Rahman
- Munshi Singh College, BR Ambedkar Bihar University, Muzaffarpur 845401, India;
| | - Sana Iram
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea;
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.T.R.); (A.H.)
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia; (M.T.R.); (A.H.)
| | - Arif Tasleem Jan
- School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185234, India;
| | - Jihoe Kim
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 712-749, Republic of Korea;
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Ali A, Kumar R, Khan A, Khan AU. Interaction of LysM BON family protein domain with carbapenems: A putative mechanism of carbapenem resistance. Int J Biol Macromol 2020; 160:212-223. [PMID: 32464197 DOI: 10.1016/j.ijbiomac.2020.05.172] [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] [Received: 01/16/2020] [Revised: 05/21/2020] [Accepted: 05/21/2020] [Indexed: 10/24/2022]
Abstract
Carbapenem resistance in Gram-negative pathogens has become a global concern for health workers worldwide. In one of our earlier studies, a Klebsiella pneumoniae-carbapenemase-2 producing strain was induced with meropenem to explore differentially expressed proteins under induced and uninduced conditions. There is, LysM domain BON family protein, was found over 12-fold expressed under the induced state. A hypothesis was proposed that LysM domain protein might have an affinity towards carbapenem antibiotics making them unavailable to bind with their target. Hence, we initiated a study to understand the binding mode of carbapenem with LysM domain protein. MICs of imipenem and meropenem against LysM clone were increased by several folds as compared to NP-6 clinical strain as well as DH5 α (PET-28a KPC-2) clone. This study further revealed a strong binding of both antibiotics to LysM domain protein. Molecular simulation studies of LysM domain protein with meropenem and imipenem for 80 ns has also showed stable structure. We concluded that overexpressed LysM domain under induced condition interacted with carbapenems, leading to enhanced resistance as proved by high MIC values. Hence, the study proved the proposed hypothesis that the LysM domain plays a significant role in the putative mechanism of antibiotics resistance.
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Affiliation(s)
- Abid Ali
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP, India
| | - Rakesh Kumar
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, Delhi 110067, India
| | - Arbab Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP, India
| | - Asad U Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP, India; Faculty of Science and Marine Environment, University Malysia Terengganu, Kuala Terengganu, Malaysia.
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Ahmed MZ, Muteeb G, Khan S, Alqahtani AS, Somvanshi P, Alqahtani MS, Ameta KL, Haque S. Identifying novel inhibitor of quorum sensing transcriptional regulator (SdiA) of Klebsiella pneumoniae through modelling, docking and molecular dynamics simulation. J Biomol Struct Dyn 2020; 39:3594-3604. [PMID: 32401149 DOI: 10.1080/07391102.2020.1767209] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
In this study, attempts have been made to identify novel inhibitor(s) of SdiA (a homolog of LuxR transcription regulator) of Klebseilla pneumoniae using various computational techniques. 4LFU was used as a template to model the structure of SdiA. ProCheck, Verify3D, Ramachandran plot scores and ProSA-Web confirmed the good quality of the model as the root mean square deviation (RMSD) between SdiA model, and 4LFU template was estimated to be 0.21 Å. The secondary structural contents of SdiA model were predicted using PDBsum. The only binding site of SdiA was identified (area = 523.083 Å2 and volume = 351.044 Å3) using CASTp. Molecular docking at three different levels [high throughput virtual screening, standard-precision (SP) and extra-precision (XP) dockings] with increasingly stringent conditions was performed using Glide on Selleck's express pick library (L3600). A total of 61 ligands were found to bind with high affinities to the active site of SdiA. Further, the effect of solvent on protein-ligand interaction was evaluated by performing molecular mechanics-general born surface area (Prime/MM-GBSA). On the basis of Prime/MM-GBSA score, molecular dynamics simulation (50 ns) was performed on the ligand (WAY-390139-A) showing lowest binding energy to confirm the stability of protein-ligand complex. Docking energy and the corresponding binding affinity of WAY-390139-A towards SdiA were estimated to be -13.005 kcal mol-1 and 3.46 × 109 M-1, respectively. Our results confirm that WAY-390139-A binds at the autoinducer binding site of SdiA with high affinity and stability and can be further exploited as potential drug against K. pneumoniae after experimental validation.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Mohammad Z Ahmed
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Ghazala Muteeb
- Department of Nursing, College of Applied Medical Sciences, King Faisal University, Saudi Arabia
| | - Saif Khan
- Department of Basic Medical and Dental Science, College of Dentistry, University of Ha'il, Ha'il, Saudi Arabia
| | - Ali S Alqahtani
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Pallavi Somvanshi
- Department of Biotechnology, TERI School of Advanced Studies, Plot No. 10, Institutional Area, Vasant Kunj, India
| | - Mohammed S Alqahtani
- Departmental of Pharmaceutics, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia
| | - Keshav Lalit Ameta
- Department of Chemistry, Mody University of Science and Technology, Lakshmangarh, Rajasthan, India
| | - Shafiul Haque
- Research and Scientific Studies Unit, College of Nursing & Allied Health Sciences, Jazan University, Jazan, Saudi Arabia
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Rahman S, Rehman MT, Rabbani G, Khan P, AlAjmi MF, Hassan MI, Muteeb G, Kim J. Insight of the Interaction between 2,4-thiazolidinedione and Human Serum Albumin: A Spectroscopic, Thermodynamic and Molecular Docking Study. Int J Mol Sci 2019; 20:E2727. [PMID: 31163649 PMCID: PMC6600547 DOI: 10.3390/ijms20112727] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2019] [Revised: 05/25/2019] [Accepted: 05/30/2019] [Indexed: 12/25/2022] Open
Abstract
Thiazolidinedione derivatives (TZDs) have attracted attention because of their pharmacological effects. For example, certain TZDs have been reported to ameliorate type II diabetes by binding and activating PPARs (peroxisome proliferator-activated receptors). Nonetheless, no information is available on the interaction between the heterocyclic 2, 4-thiazolidinedione (2,4-TZD) moiety and serum albumin, which could affect the pharmacokinetics and pharmacodynamics of TZDs. In this study, we investigated the binding of 2,4-TZD to human serum albumin (HSA). Intrinsic fluorescence spectroscopy revealed a 1:1 binding stoichiometry between 2,4-TZD and HSA with a binding constant (Kb) of 1.69 ± 0.15 × 103 M-1 at 298 K. Isothermal titration calorimetry studies showed that 2,4-TZD/HSA binding was an exothermic and spontaneous reaction. Molecular docking analysis revealed that 2,4-TZD binds to HSA subdomain IB and that the complex formed is stabilized by van der Waal's interactions and hydrogen bonds. Molecular dynamics simulation confirmed the stability of the HSA-TZD complex. Further, circular dichroism and 3D fluorescence studies showed that the global conformation of HSA was slightly altered by 2,4-TZD binding, enhancing its stability. The results obtained herein further help in understanding the pharmacokinetic properties of thiazolidinedione.
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Affiliation(s)
- Safikur Rahman
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 712-749, Korea.
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Gulam Rabbani
- Nano Diagnostics; Devices (NDD), Room B-312 IT, Medical Fusion Center, Gumidae-ro, 350-27, Gumi-si, Gyeongbuk 39253, Korea.
| | - Parvez Khan
- Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India.
| | - Mohamed F AlAjmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Md Imtaiyaz Hassan
- Center for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India.
| | - Ghazala Muteeb
- Department of Nursing, College of Applied Medical Sciences, King Faisal University, 31982 Al-Ahsa, Saudi Arabia.
| | - Jihoe Kim
- Department of Medical Biotechnology, Yeungnam University, Gyeongsan 712-749, Korea.
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Hussain A, AlAjmi MF, Rehman MT, Amir S, Husain FM, Alsalme A, Siddiqui MA, AlKhedhairy AA, Khan RA. Copper(II) complexes as potential anticancer and Nonsteroidal anti-inflammatory agents: In vitro and in vivo studies. Sci Rep 2019; 9:5237. [PMID: 30918270 PMCID: PMC6437194 DOI: 10.1038/s41598-019-41063-x] [Citation(s) in RCA: 146] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 02/18/2019] [Indexed: 02/02/2023] Open
Abstract
Copper-based compounds are promising entities for target-specific next-generation anticancer and NSAIDS therapeutics. In lieu of this, benzimidazole scaffold plays an important role, because of their wide variety of potential functionalizations and coordination modes. Herein, we report three copper complexes 1-3 with benzimidazole-derived scaffolds, a biocompatible molecule, and secondary ligands viz, 1-10-phenanthroline and 2,2'-bipyridyl. All the copper complexes have been designed, synthesized and adequately characterized using various spectroscopic techniques. In-vitro, human serum albumin (HSA) binding was also carried out using fluorescence technique and in-silico molecular modeling studies, which exhibited significant binding affinities of the complexes with HSA. Furthermore, copper complexes 1-3 were tested for biological studies, i.e., anticancer as well as NSAIDS. In vitro cytotoxicity results were carried out on cultured MCF-7 cell lines. To get the insight over the mechanism of action, GSH depletion and change in lipid peroxidation were tested and thus confirmed the role of ROS generation, responsible for the cytotoxicity of the complexes 1-3. Moreover, the copper complexes 1-3 were tested for potential to act as NSAIDS on albino rats and mice in animal studies in-vivo. Additionally, we also predicted the mechanism of action of the copper complexes 1-3 using molecular modeling studies with COX-2 inhibitor.
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Affiliation(s)
- Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Saudi Arabia
| | - Mohamed Fahad AlAjmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Saudi Arabia
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh, 11451, Saudi Arabia
| | - Samira Amir
- Department of Chemistry, College of Science and General Studies, Alfaisal University, Riyadh, Saudi Arabia
| | - Fohad Mabood Husain
- Department of Food Science and Nutrition, Faculty of Food and Agricultural Sciences, King Saud University, 2460, Riyadh, 11451, Saudi Arabia
| | - Ali Alsalme
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia
| | - Maqsood Ahmad Siddiqui
- Al-Jeraisy Chair for DNA Research, Zoology Department, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Abdulaziz A AlKhedhairy
- Al-Jeraisy Chair for DNA Research, Zoology Department, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia
| | - Rais Ahmad Khan
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.
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AlAjmi MF, Hussain A, Rehman MT, Khan AA, Shaikh PA, Khan RA. Design, Synthesis, and Biological Evaluation of Benzimidazole-Derived Biocompatible Copper(II) and Zinc(II) Complexes as Anticancer Chemotherapeutics. Int J Mol Sci 2018; 19:ijms19051492. [PMID: 29772746 PMCID: PMC5983663 DOI: 10.3390/ijms19051492] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 05/07/2018] [Accepted: 05/12/2018] [Indexed: 01/10/2023] Open
Abstract
Herein, we have synthesized and characterized a new benzimidazole-derived “BnI” ligand and its copper(II) complex, [Cu(BnI)2], 1, and zinc(II) complex, [Zn(BnI)2], 2, using elemental analysis and various spectroscopic techniques. Interaction of complexes 1 and 2 with the biomolecules viz. HSA (human serum albumin) and DNA were studied using absorption titration, fluorescence techniques, and in silico molecular docking studies. The results exhibited the significant binding propensity of both complexes 1 and 2, but complex 1 showed more avid binding to HSA and DNA. Also, the nuclease activity of 1 and 2 was analyzed for pBR322 DNA, and the results obtained confirmed the potential of the complexes to cleave DNA. Moreover, the mechanistic pathway was studied in the presence of various radical scavengers, which revealed that ROS (reactive oxygen species) are responsible for the nuclease activity in complex 1, whereas in complex 2, the possibility of hydrolytic cleavage also exists. Furthermore, the cytotoxicity of the ligand and complexes 1 and 2 were studied on a panel of five different human cancer cells, namely: HepG2, SK-MEL-1, HT018, HeLa, and MDA-MB 231, and compared with the standard drug, cisplatin. The results are quite promising against MDA-MB 231 (breast cancer cell line of 1), with an IC50 value that is nearly the same as the standard drug. Apoptosis was induced by complex 1 on MDA-MB 231 cells predominantly as studied by flow cytometry (FACS). The adhesion and migration of cancer cells were also examined upon treatment of complexes 1 and 2. Furthermore, the in vivo chronic toxicity profile of complexes 1 and 2 was also studied on all of the major organs of the mice, and found them to be less toxic. Thus, the results warrant further investigations of complex 1.
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Affiliation(s)
- Mohamed F AlAjmi
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
| | - Afzal Hussain
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
| | - Md Tabish Rehman
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
| | - Azmat Ali Khan
- Department of Pharmaceutical Chemistry, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
| | - Perwez Alam Shaikh
- Department of Pharmacognosy, College of Pharmacy, King Saud University, P.O. Box 2457, Riyadh 11451, Saudi Arabia.
| | - Rais Ahmad Khan
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
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Maryam L, Sharma A, Azam MW, Khan SN, Khan AU. Understanding the mode of binding mechanism of doripenem to human serum albumin: Spectroscopic and molecular docking approaches. J Mol Recognit 2018; 31:e2710. [PMID: 29603446 DOI: 10.1002/jmr.2710] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 02/14/2018] [Accepted: 02/18/2018] [Indexed: 12/12/2022]
Abstract
The infections caused by multidrug resistant bacteria are widely treated with carabapenem antibiotics as a drug of choice, and human serum albumin (HSA) plays a vital role in binding with drugs and affecting its rate of delivery and efficacy. So, we have initiated this study to characterize the mechanism of doripenem binding and to locate its site of binding on HSA by using spectroscopic and docking approaches. The binding of doripenem leads to alteration of the environment surrounding Trp-214 residue of HSA as observed by UV spectroscopic study. Fluorescence spectroscopic study revealed considerable interaction and complex formation of doripenem and HSA as indicated by Ksv and Kq values of the order of 104 M-1 and 1012 M-1 s-1 , respectively. Furthermore, doripenem quenches the fluorescence of HSA spontaneously on a single binding site with binding constant of the order of 103 M-1 , through an exothermic process. Van der Waals forces and hydrogen bonding are the major forces operating to stabilize HSA-doripenem complex. Circular dichroism spectroscopic study showed changes in the structure of HSA upon doripenem binding. Drug displacement and molecular docking studies revealed that the binding site of doripenem on HSA is located on subdomain IB and III A. This study concludes that, due to significant interaction of doripenem on either subdomain IB or IIIA of HSA, the availability of doripenem on the target site may be compromised. Hence, there is a possibility of unavailability of threshold amount of drug to be reached to the target; consequently, resistance may develop in the bacterial population.
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Affiliation(s)
- Lubna Maryam
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Ashima Sharma
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Mohd W Azam
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Shahper N Khan
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
| | - Asad U Khan
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, India
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Rehman MT, Ahmed S, Khan AU. Interaction of meropenem with ‘N’ and ‘B’ isoforms of human serum albumin: a spectroscopic and molecular docking study. J Biomol Struct Dyn 2015; 34:1849-64. [DOI: 10.1080/07391102.2015.1094411] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Md. Tabish Rehman
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202 002, India
| | - Sarfraz Ahmed
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202 002, India
| | - Asad U. Khan
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202 002, India
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Rehman MT, Shamsi H, Khan AU. Insight into the binding mechanism of imipenem to human serum albumin by spectroscopic and computational approaches. Mol Pharm 2014; 11:1785-97. [PMID: 24745377 DOI: 10.1021/mp500116c] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The mechanism of interaction between imipenem and HSA was investigated by various techniques like fluorescence, UV.vis absorbance, FRET, circular dichroism, urea denaturation, enzyme kinetics, ITC, and molecular docking. We found that imipenem binds to HSA at a high affinity site located in subdomain IIIA (Sudlow's site I) and a low affinity site located in subdomain IIA.IIB. Electrostatic interactions played a vital role along with hydrogen bonding and hydrophobic interactions in stabilizing the imipenem.HSA complex at subdomain IIIA, while only electrostatic and hydrophobic interactions were present at subdomain IIA.IIB. The binding and thermodynamic parameters obtained by ITC showed that the binding of imipenem to HSA was a spontaneous process (ΔGD⁰(D)= -32.31 kJ mol(-1) for high affinity site and ΔGD⁰(D) = -23.02 kJ mol(-1) for low affinity site) with binding constants in the range of 10(4)-10(5) M(-1). Spectroscopic investigation revealed only one binding site of imipenem on HSA (Ka∼10(4) M(-1)). FRET analysis showed that the binding distance between imipenem and HSA (Trp-214) was optimal (r = 4.32 nm) for quenching to occur. Decrease in esterase-like activity of HSA in the presence of imipenem showed that Arg-410 and Tyr-411 of subdomain IIIA (Sudlow's site II) were directly involved in the binding process. CD spectral analysis showed altered conformation of HSA upon imipenem binding. Moreover, the binding of imipenem to subdomain IIIA (Sudlow's site II) of HSA also affected its folding pathway as clear from urea-induced denaturation studies.
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Affiliation(s)
- Md Tabish Rehman
- Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit, Aligarh Muslim University , Aligarh, Uttar Pradesh, 202 002, India
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Rehman MT, Faheem M, Khan AU. An insight into the biophysical characterization of different states of cefotaxime hydrolyzing β-lactamase 15 (CTX-M-15). J Biomol Struct Dyn 2014; 33:625-38. [PMID: 24650131 DOI: 10.1080/07391102.2014.899925] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Cefotaxime hydrolyzing β-lactamase-15 (CTX-M-15) is encoded by blaCTX-M-15 gene present on plasmid of various Gram-negative bacteria, such as E. coli, E. cloacae, K. pneumoniae, etc. The widespread dissemination of CTX-M-15 harboring bacteria in hospital as well as community settings is a universal threat as they are resistant to various clinically significant antibiotics. In order to gain an insight into the folding mechanism of CTX-M-15, we carried out pH-induced denaturation study by monitoring Trp fluorescence, far-UV circular dichroism (CD), and ANS fluorescence. We found that the pH-induced denaturation of CTX-M-15 was a three-step process with the accumulation of two stable folding intermediates (XI at pH 2.5 and XII at pH 1.5) in the folding pathway. The intermediates were further characterized by far-UV and near-UV CD analysis, Trp fluorescence, ANS fluorescence, three-dimensional fluorescence, acrylamide quenching, dynamic light scattering, and thermal denaturation studies. We found that XI state lacked tertiary structure but retained most of the secondary structure, its Trp residues were partially exposed to the solvent and its hydrophobic patches were highly accessible to ANS. On the other hand, a complete disruption of tertiary structure along with more than 50% loss in secondary structure was observed in XII state. We conclude that the XI state of CTX-M-15 at pH 2.5 had all the characteristics of a molten globule (MG) state, while its XII state at pH 1.5 was more similar to pre-molten globule (PMG) state. ANS fluorescence also showed that the binding of ANS in XII state was lower than that in the XI state. We propose that the accumulation of MG- and PMG-states was due to separation (at pH 2.5) and then unfolding (at pH 1.5) of the αβα-fold of CTX-M-15, respectively.
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Affiliation(s)
- Md Tabish Rehman
- a Medical Microbiology and Molecular Biology Laboratory, Interdisciplinary Biotechnology Unit , Aligarh Muslim University , Aligarh , UP 202002 , India
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