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Yadav R, Nandy A, Bisoi A, Mukherjee S. Exploring the Specific Role of Iron Center in the Catalytic Activity of Human Serum Transferrin: CTAB-Induced Conformational Changes and Sequestration by Mixed Micelles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:6172-6186. [PMID: 38467540 DOI: 10.1021/acs.langmuir.3c03414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/13/2024]
Abstract
Conformational changes play a seminal role in modulating the activity of proteins. This concept becomes all the more relevant in the context of metalloproteins, owing to the formation of specific conformation(s) induced by internal perturbations (like a change in pH, ligand binding, or receptor binding), which may carry out the binding and release of the metal ion/ions from the metal binding center of the protein. Herein, we investigated the conformational changes of an iron-binding protein, monoferric human serum transferrin (Fe-hTF), using several spectroscopic approaches. We could reversibly tune the cetyltrimethylammonium bromide (CTAB)-induced conformation of the protein, exploiting the concept of mixed micelles formed by three sequestrating agents: (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) hydrate (CHAPS) and two bile salts, namely, sodium cholate (NaC) and sodium deoxycholate (NaDC). The formation of mixed micelles between CTAB and these reagents (CHAPS/NaC/NaDC) results in the sequestration of CTAB molecules from the protein environment and aids the protein in reattaining its native-like structure. However, the guanidinium hydrochloride-induced denatured Fe-hTF did not acquire its native-like structure using these sequestrating agents, which substantiates the exclusive role of mixed micelles in the present study. Apart from this, we found that the conformation of transferrin (adopted in the presence of CTAB) displays pronounced esterase-like activity toward the para-nitrophenyl acetate (PNPA) substrate as compared to native transferrin. We also outlined the impact of the iron center and amino acids surrounding the iron center on the effective catalytic activity in the CTAB medium. We estimated ∼3 times higher specific catalytic efficiency for the iron-depleted Apo-hTF compared to the fully iron-saturated Fe2-hTF in the presence of CTAB.
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Affiliation(s)
- Rahul Yadav
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Atanu Nandy
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Asim Bisoi
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
| | - Saptarshi Mukherjee
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462 066, Madhya Pradesh, India
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2
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Sandu N, Popescu AI, Chilom CG. Probing the interaction of fisetin with human serum transferrin via spectroscopic and molecular docking approaches. J Biomol Struct Dyn 2022; 40:9613-9619. [PMID: 34098861 DOI: 10.1080/07391102.2021.1934545] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The binding of fisetin to human serum transferrin (HST) was investigated by spectroscopic (steady-state fluorescence, synchronous fluorescence, Förster resonance energy transfer) and molecular docking approaches. HST fluorescence is quenched by fisetin by a static process. The binding takes place with a moderate affinity and it is driven by hydrogen bonding and van der Waals forces. Synchronous fluorescence study indicates that Trp is more involved in the fluorescent quenching of HST by fisetin than Tyr. The energy transfer between HST and fisetin occurs at a distance of 2.31 nm confirming the results obtained by fluorescence. The binding of fisetin to HST favors thermal denaturation of HST conformation. The transition temperature for HST was obtained at 53.81 °C while the presence of the fisetin led to its change to 49.06 °C. The molecular docking of fisetin to HST confirms the results obtained by the spectroscopic experiments showing a moderate affinity of fisetin for HST.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Nicoleta Sandu
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Romania
| | - Aurel I Popescu
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Romania
| | - Claudia G Chilom
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Romania
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3
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Cazacu N, Popescu AI, Chilom CG. Spectroscopic and molecular docking approach of the interaction of vitamins with human serum transferrin. Chem Phys 2022. [DOI: 10.1016/j.chemphys.2022.111459] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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4
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Chilom CG, Sandu N, Iftimie S, Bălăşoiu M, Rogachev A, Orelovich O, Stolyar S. Interactions of Chemically Synthesized Ferrihydrite Nanoparticles with Human Serum Transferrin: Insights from Fluorescence Spectroscopic Studies. Int J Mol Sci 2021; 22:ijms22137034. [PMID: 34210014 PMCID: PMC8268179 DOI: 10.3390/ijms22137034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/26/2021] [Accepted: 06/26/2021] [Indexed: 01/21/2023] Open
Abstract
Human serum transferrin (HST) is a glycoprotein involved in iron transport that may be a candidate for functionalized nanoparticles to bind and target cancer cells. In this study, the effects of the simple and doped with cobalt (Co) and copper (Cu) ferrihydrite nanoparticles (Fh-NPs, Cu-Fh-NPs, and Co-Fh-NPs) were studied by spectroscopic and molecular approaches. Fluorescence spectroscopy revealed a static quenching mechanism for all three types of Fh-NPs. All Fh-NPs interacted with HST with low affinity, and the binding was driven by hydrogen bonding and van der Waals forces for simple Fh-NPs and by hydrophobic interactions for Cu-Fh-NPs and Co-Fh-NPs binding, respectively. Of all samples, simple Fh-NPs bound the most to the HST binding site. Fluorescence resonance energy transfer (FRET) allowed the efficient determination of the energy transfer between HST and NPs and the distance at which the transfer takes place and confirmed the mechanism of quenching. The denaturation of the HST is an endothermic process, both in the case of apo HST and HST in the presence of the three types of Fh-NPs. Molecular docking studies revealed that Fh binds with a low affinity to HST (Ka = 9.17 × 103 M−1) in accord with the fluorescence results, where the interaction between simple Fh-NPs and HST was described by a binding constant of 9.54 × 103 M−1.
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Affiliation(s)
- Claudia G. Chilom
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Str Atomistilor 405, CP MG 11, RO-077125 Măgurele, Romania; (N.S.); (S.I.)
- Correspondence:
| | - Nicoleta Sandu
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Str Atomistilor 405, CP MG 11, RO-077125 Măgurele, Romania; (N.S.); (S.I.)
| | - Sorina Iftimie
- Department of Electricity, Solid Physics and Biophysics, Faculty of Physics, University of Bucharest, Str Atomistilor 405, CP MG 11, RO-077125 Măgurele, Romania; (N.S.); (S.I.)
| | - Maria Bălăşoiu
- Joint Institute for Nuclear Research, Joliot-Curie No. 6, 141980 Dubna, Russia; (M.B.); (A.R.); (O.O.)
- Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering, RO-077125 Măgurele, Romania
- Moscow Institute of Physics and Technology, Institutskiy Per. No. 9, 141701 Dolgoprudniy, Russia
| | - Andrey Rogachev
- Joint Institute for Nuclear Research, Joliot-Curie No. 6, 141980 Dubna, Russia; (M.B.); (A.R.); (O.O.)
- Moscow Institute of Physics and Technology, Institutskiy Per. No. 9, 141701 Dolgoprudniy, Russia
| | - Oleg Orelovich
- Joint Institute for Nuclear Research, Joliot-Curie No. 6, 141980 Dubna, Russia; (M.B.); (A.R.); (O.O.)
| | - Sergey Stolyar
- Krasnoyarsk Science Center of the Siberian, Branch of the Russian Academy of Sciences, Akademgorodok St. No. 50, 660036 Krasnoyarsk, Russia;
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5
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Sandu N, Chilom CG, Popescu AI. Structural and molecular aspects of flavonoids as ligands for serum transferrin. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 254:119600. [PMID: 33677206 DOI: 10.1016/j.saa.2021.119600] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
Human serum transferrin (HST) acts as a carrier for Fe3+ and other ions. Binding of flavonoids to HST produces changes in the protein structure with direct implication on iron delivery into cells. We investigate the binding mechanism and affinity towards HST of three flavonoids: rutin, luteolin, and apigenin by different techniques: UV-Vis, fluorescence, fluorescence resonance energy transfer (FRET) combined with molecular docking. UV-Vis results indicate an interaction between flavonoids and HST. It was observed that HST fluorescence was quenched by these three flavonoids via a static process. All the interactions were moderate and the main driving forces are hydrophobic (ΔH > 0 and ΔS > 0) for rutin and luteolin binding or electrostatic (ΔH < 0 and ΔS > 0) for apigenin binding. FRET and molecular docking studies confirm the fluorescence static quenching mechanism by flavonoid binding. The binding of all three flavonoids increases HST stability. These results present the potential use of HST in target-oriented delivery of flavonoids and possibly other drugs into cells.
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Affiliation(s)
- Nicoleta Sandu
- Department of Electricity, Solid State and Biophysics, Faculty of Physics, University of Bucharest, Măgurele, Romania
| | - Claudia G Chilom
- Department of Electricity, Solid State and Biophysics, Faculty of Physics, University of Bucharest, Măgurele, Romania.
| | - Aurel I Popescu
- Department of Electricity, Solid State and Biophysics, Faculty of Physics, University of Bucharest, Măgurele, Romania
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6
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Dangi V, Baral M, Kanungo BK. Photophysical Studies of a Catechol Based Polyfunctional Dipodal Chelator: Application for Optical Probe for Selective Detection of Fe(III). J Fluoresc 2020; 30:1131-1149. [PMID: 32648173 DOI: 10.1007/s10895-020-02583-2] [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: 05/11/2020] [Accepted: 06/30/2020] [Indexed: 10/23/2022]
Abstract
A novel catechol based dipodal fluorescent chelator N,N'-bis[3-[(E)-(2,3-dihydroxyphenyl)methyleneamino]propyl]propanediamide(MPC), has been developed and its photophysical behaviour was studied by experimental (UV-VIS and fluorescence) and DFT method. The design of the molecule has been inspired from the naturally occurring siderophore enterobactin, a catechol based chelator with amide linkage, that shows an excellent binding efficiency towards Fe(III). The dipodal molecule (MPC) presented here, carries two catechol pendant binding moieties linked to the malonate central unit through propylene spacers by amide linkage. MPC showed good selectivity for Fe(III) at 10-4 M concentration in aqueous medium amongst the biologically and environmentally important metal ions chosen viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), by demonstrating a remarkable quenching in the fluorescent emission from 262 a.u. to 55 a.u. at λmax = 477 nm. Also, the pre-organized assembled ligand favored an efficient Fe (III) encapsulation through coordination by imine nitrogen and catecholate oxygen donors. High formation constant (log β = 31.3) for 1:1 metal-ligand complex evaluated by both potentiometric and spectrophotometric methods, established the strong binding efficiency of the ligand for Fe(III) metal ion. The binding stoichiometry in the complex was also confirmed from Stern -Volmer and Hill Plot analysis. Further investigation on the emission behavior of MPC in a completely DMSO system explored its suitability for extensive applications in the areas such as, metallurgy, material science, iron contamination remedial in the materials etc.. DFT studies suggest that the ligand displays a U-shaped geometry with a parallel π-stacking and the hydrogen bond between two arms. The experimental infrared, electronic, fluorescence, 1H nmr, 13C nmr spectra were correlated with the theoretical results. The nature of electronic transitions were identified from the TDDFT calculation. The ligand forms a hexa-coordinated complex with six Fe-O bonds extending an orthorhombic geometry due distortion from a regular octahedron.
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Affiliation(s)
- Vijay Dangi
- Department of Chemistry, National Institute of Technology, Kurukshetra, Haryana, 136119, India
| | - Minati Baral
- Department of Chemistry, National Institute of Technology, Kurukshetra, Haryana, 136119, India.
| | - B K Kanungo
- Department of Chemistry, Sant Longowal Institute of Engineering & Technology, Longowal, 148106, India
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7
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Qiao H, Li B, Zhang H, Liu D, Diao H, Sun G, Xie J. Effects of the equimolarly mixed cationic–nonionic surfactants of didodecyldimethylammonium bromide and polyoxyethylene sorbitan monooleate 80 on serum proteins—spectroscopic study. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2018; 187:151-161. [DOI: 10.1016/j.jphotobiol.2018.08.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Revised: 08/06/2018] [Accepted: 08/12/2018] [Indexed: 02/07/2023]
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8
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Correia I, Chorna I, Cavaco I, Roy S, Kuznetsov ML, Ribeiro N, Justino G, Marques F, Santos-Silva T, Santos MFA, Santos HM, Capelo JL, Doutch J, Pessoa JC. Interaction of [V IV O(acac) 2 ] with Human Serum Transferrin and Albumin. Chem Asian J 2017. [PMID: 28651041 DOI: 10.1002/asia.201700469] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
[VO(acac)2 ] is a remarkable vanadium compound and has potential as a therapeutic drug. It is important to clarify how it is transported in blood, but the reports addressing its binding to serum proteins have been contradictory. We use several spectroscopic and mass spectrometric techniques (ESI and MALDI-TOF), small-angle X-ray scattering and size exclusion chromatography (SEC) to characterize solutions containing [VO(acac)2 ] and either human serum apotransferrin (apoHTF) or albumin (HSA). DFT and modeling protein calculations are carried out to disclose the type of binding to apoHTF. The measured circular dichroism spectra, SEC and MALDI-TOF data clearly prove that at least two VO-acac moieties may bind to apoHTF, most probably forming [VIV O(acac)(apoHTF)] complexes with residues of the HTF binding sites. No indication of binding of [VO(acac)2 ] to HSA is obtained. We conclude that VIV O-acac species may be transported in blood by transferrin. At very low complex concentrations speciation calculations suggest that [(VO)(apoHTF)] species form.
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Affiliation(s)
- Isabel Correia
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
| | - Ielyzaveta Chorna
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
| | - Isabel Cavaco
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.,Departamento de Química e Farmácia, Universidade do Algarve, Campus de Gambelas, 8005-139, Faro, Portugal
| | - Somnath Roy
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.,Department of Chemistry, Ananda Chandra College, Jalpaiguri, West Bengal, India
| | - Maxim L Kuznetsov
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
| | - Nádia Ribeiro
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
| | - Gonçalo Justino
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
| | - Fernanda Marques
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal.,Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, Estrada Nacional 10 (km 139.7), 2695-066, Bobadela LRS, Portugal
| | - Teresa Santos-Silva
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
| | - Marino F A Santos
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
| | - Hugo M Santos
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.,PROTEOMASS Scientific Society, Madan Park, Rua dos Inventores, 2825-152, Caparica, Portugal
| | - José L Capelo
- UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.,PROTEOMASS Scientific Society, Madan Park, Rua dos Inventores, 2825-152, Caparica, Portugal
| | - James Doutch
- ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK
| | - João Costa Pessoa
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisboa, Portugal
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Kaspler P, Lazic S, Forward S, Arenas Y, Mandel A, Lilge L. A ruthenium(ii) based photosensitizer and transferrin complexes enhance photo-physical properties, cell uptake, and photodynamic therapy safety and efficacy. Photochem Photobiol Sci 2016; 15:481-95. [DOI: 10.1039/c5pp00450k] [Citation(s) in RCA: 93] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mixing the novel Ru2+complex TLD1433 with transferrin prior to administration generates a photosensitizing drug with reduced dark toxicity and improved photophysical properties including NIR activation.
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Affiliation(s)
| | | | - Sarah Forward
- University Health Network
- Princess Margaret Cancer Research Tower and University of Toronto
- Department of Medical Biophysics
- Toronto
- Canada
| | | | | | - Lothar Lilge
- University Health Network
- Princess Margaret Cancer Research Tower and University of Toronto
- Department of Medical Biophysics
- Toronto
- Canada
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10
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Noguera ME, Roman EA, Rigal JB, Cousido-Siah A, Mitschler A, Podjarny A, Santos J. Structural characterization of metal binding to a cold-adapted frataxin. J Biol Inorg Chem 2015; 20:653-64. [PMID: 25832196 DOI: 10.1007/s00775-015-1251-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 03/02/2015] [Indexed: 12/30/2022]
Abstract
Frataxin is an evolutionary conserved protein that participates in iron metabolism. Deficiency of this small protein in humans causes a severe neurodegenerative disease known as Friedreich's ataxia. A number of studies indicate that frataxin binds iron and regulates Fe-S cluster biosynthesis. Previous structural studies showed that metal binding occurs mainly in a region of high density of negative charge. However, a comprehensive characterization of the binding sites is required to gain further insights into the mechanistic details of frataxin function. In this work, we have solved the X-ray crystal structures of a cold-adapted frataxin from a psychrophilic bacterium in the presence of cobalt or europium ions. We have identified a number of metal-binding sites, mainly solvent exposed, several of which had not been observed in previous studies on mesophilic homologues. No major structural changes were detected upon metal binding, although the structures exhibit significant changes in crystallographic B-factors. The analysis of these B-factors, in combination with crystal packing and RMSD among structures, suggests the existence of localized changes in the internal motions. Based on these results, we propose that bacterial frataxins possess binding sites of moderate affinity for a quick capture and transfer of iron to other proteins and for the regulation of Fe-S cluster biosynthesis, modulating interactions with partner proteins.
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Affiliation(s)
- Martín E Noguera
- Instituto de Química y Físico-Química Biológicas, Universidad de Buenos Aires, Junín 956, 1113AAD, Buenos Aires, Argentina
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11
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Montecinos-Franjola F, James NG, Concha-Marambio L, Brunet JE, Lagos R, Monasterio O, Jameson DM. Single tryptophan mutants of FtsZ: nucleotide binding/exchange and conformational transitions. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1193-200. [PMID: 24704635 DOI: 10.1016/j.bbapap.2014.03.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 03/24/2014] [Accepted: 03/26/2014] [Indexed: 11/27/2022]
Abstract
Cell division protein FtsZ cooperatively self-assembles into straight filaments when bound to GTP. A set of conformational changes that are linked to FtsZ GTPase activity are involved in the transition from straight to curved filaments that eventually disassemble. In this work, we characterized the fluorescence of single Trp mutants as a reporter of the predicted conformational changes between the GDP- and GTP-states of Escherichia coli FtsZ. Steady-state fluorescence characterization showed the Trp senses different environments and displays low solvent accessibility. Time-resolved fluorescence data indicated that the main conformational changes in FtsZ occur at the interaction surface between the N and C domains, but also minor rearrangements were detected in the bulk of the N domain. Surprisingly, despite its location near the bottom protofilament interface at the C domain, the Trp 275 fluorescence lifetime did not report changes between the GDP and GTP states. The equilibrium unfolding of FtsZ features an intermediate that is stabilized by the nucleotide bound in the N-domain as well as by quaternary protein-protein interactions. In this context, we characterized the unfolding of the Trp mutants using time-resolved fluorescence and phasor plot analysis. A novel picture of the structural transition from the native state in the absence of denaturant, to the solvent-exposed unfolded state is presented. Taken together our results show that conformational changes between the GDP and GTP states of FtsZ, such as those observed in FtsZ unfolding, are restricted to the interaction surface between the N and C domains.
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Affiliation(s)
- Felipe Montecinos-Franjola
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu 96813, HI, USA.
| | - Luis Concha-Marambio
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Juan E Brunet
- Instituto de Química, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, Valparaíso 2373223, Chile.
| | - Rosalba Lagos
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - Octavio Monasterio
- Laboratorio de Biología Estructural y Molecular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago 7800024, Chile.
| | - David M Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu 96813, HI, USA.
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12
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Effect of electron withdrawing anchoring groups on the optoelectronic properties of pyrene sensitizers and their interaction with TiO2: A combined experimental and theoretical approach. J Photochem Photobiol A Chem 2013. [DOI: 10.1016/j.jphotochem.2013.07.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Iron binding at specific sites within the octameric HbpS protects streptomycetes from iron-mediated oxidative stress. PLoS One 2013; 8:e71579. [PMID: 24013686 PMCID: PMC3754957 DOI: 10.1371/journal.pone.0071579] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 07/08/2013] [Indexed: 12/26/2022] Open
Abstract
The soil bacterium Streptomyces reticuli secretes the octameric protein HbpS that acts as a sensory component of the redox-signalling pathway HbpS-SenS-SenR. This system modulates a genetic response on iron- and haem-mediated oxidative stress. Moreover, HbpS alone provides this bacterium with a defence mechanism to the presence of high concentrations of iron ions and haem. While the protection against haem has been related to its haem-binding and haem-degrading activity, the interaction with iron has not been studied in detail. In this work, we biochemically analyzed the iron-binding activity of a set of generated HbpS mutant proteins and present evidence showing the involvement of one internal and two exposed D/EXXE motifs in binding of high quantities of ferrous iron, with the internal E78XXE81 displaying the tightest binding. We additionally show that HbpS is able to oxidize ferrous to ferric iron ions. Based on the crystal structure of both the wild-type and the mutant HbpS-D78XXD81, we conclude that the local arrangement of the side chains from the glutamates in E78XXE81 within the octameric assembly is a pre-requisite for interaction with iron. The data obtained led us to propose that the exposed and the internal motif build a highly specific route that is involved in the transport of high quantities of iron ions into the core of the HbpS octamer. Furthermore, physiological studies using Streptomyces transformants secreting either wild-type or HbpS mutant proteins and different redox-cycling compounds led us to conclude that the iron-sequestering activity of HbpS protects these soil bacteria from the hazardous side effects of peroxide- and iron-based oxidative stress.
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14
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Estrada JG, Sánchez-Delgado RA. Spectroscopic Study of the Interactions of Ruthenium-Ketoconazole Complexes of Known Antiparasitic Activity with Human Serum Albumin and Apotransferrin. J MEX CHEM SOC 2013; 57:169-174. [PMID: 24391686 PMCID: PMC3880155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The pharmacological properties of any drug are related to their ability to interact with macromolecular blood components. The interaction of human serum albumin (HSA) and apotransferrin (ATf) with six RuII complexes containing ketoconazole (KTZ), which we have previously reported to be active against Leishmania major and Trypanosoma cruzi, has been investigated by monitoring the tryptophan fluorescence intensity of each protein upon incremental addition of the complexes. All the Ru-KTZ derivatives, namely cis-fac-[RuIICl2(DMSO)3(KTZ)] (1), cis-[RuIICl2(bipy)(DMSO)(KTZ)] (2), [RuII(η6-p-cymene)Cl2(KTZ)] (3), [RuII(η6-p-cymene)(en)(KTZ)][BF4]2 (4), [RuII(η6-p-cymene)(bipy)(KTZ)][BF4]2 (5), and [RuII(η6-p-cymene)(acac)(KTZ)][BF4] (6) are able to quench the intrinsic fluorescence of HSA and ATf at 27 °C. Analysis of the spectroscopic data using Stern-Volmer plots indicates that in both cases the quenching takes place principally through a static mechanism involving the formation of Ru complex-protein adducts; further analysis of the fluorescence data allowed the estimation of apparent association constants and the number of binding sites for each protein and each compound. The results indicate that both HSA and ATf are possible effective transporters for Ru-KTZ antiparasitic drugs.
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Affiliation(s)
- Jesús G Estrada
- Brooklyn College and The Graduate Center, The City University of New York 2900 Bedford Ave., Brooklyn, NY 11210, USA
| | - Roberto A Sánchez-Delgado
- Brooklyn College and The Graduate Center, The City University of New York 2900 Bedford Ave., Brooklyn, NY 11210, USA
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15
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Mazuryk O, Kurpiewska K, Lewiński K, Stochel G, Brindell M. Interaction of apo-transferrin with anticancer ruthenium complexes NAMI-A and its reduced form. J Inorg Biochem 2012; 116:11-8. [PMID: 23010324 DOI: 10.1016/j.jinorgbio.2012.07.017] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 06/12/2012] [Accepted: 07/22/2012] [Indexed: 11/26/2022]
Abstract
NAMI-A i.e. (ImH)[trans-RuCl(4)(DMSO)(Im)] (where Im is imidazole) is a ruthenium(III) complex with promising antimetastatic activity, which has been classified for II phase clinical trial. In this study, its binding properties toward apo-transferrin (apo-Tf) with regard to its hydrolytic and redox behavior are systematically investigated by the use of fluorescence spectroscopy. The reaction of NAMI-A and its reduced form with apo-Tf is proceeded by formation of aqua derivatives and the presence of at least one labile aqua ligand is sufficient to form adducts. It is found that presence of bicarbonate is not necessary for interaction of studied ruthenium complexes with apo-Tf. The calculated association constants for both NAMI-A and its reduced form are very similar with the values of 1.28 × 10(4)M(-1) and 1.36 × 10(4)M(-1) at 37 °C, respectively however, the reduced derivatives reach the equilibrium ca. 8-10 times slower. The percentage of ruthenium content in protein fractions separated from protein-unbounded ruthenium by using FPLC (fast protein liquid chromatography) method is rather high and depends on redox state of the complex, for most samples is found higher for reduced species.
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Affiliation(s)
- Olga Mazuryk
- Department of Inorganic Chemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland
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16
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Brisson L, El Bakkali-Taheri N, Giorgi M, Fadel A, Kaizer J, Réglier M, Tron T, Ajandouz EH, Simaan AJ. 1-Aminocyclopropane-1-carboxylic acid oxidase: insight into cofactor binding from experimental and theoretical studies. J Biol Inorg Chem 2012; 17:939-49. [PMID: 22711330 DOI: 10.1007/s00775-012-0910-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Accepted: 05/29/2012] [Indexed: 12/25/2022]
Abstract
1-Aminocyclopropane-1-carboxylic acid oxidase (ACCO) is a nonheme Fe(II)-containing enzyme that is related to the 2-oxoglutarate-dependent dioxygenase family. The binding of substrates/cofactors to tomato ACCO was investigated through kinetics, tryptophan fluorescence quenching, and modeling studies. α-Aminophosphonate analogs of the substrate (1-aminocyclopropane-1-carboxylic acid, ACC), 1-aminocyclopropane-1-phosphonic acid (ACP) and (1-amino-1-methyl)ethylphosphonic acid (AMEP), were found to be competitive inhibitors versus both ACC and bicarbonate (HCO(3)(-)) ions. The measured dissociation constants for Fe(II) and ACC clearly indicate that bicarbonate ions improve both Fe(II) and ACC binding, strongly suggesting a stabilization role for this cofactor. A structural model of tomato ACCO was constructed and used for docking experiments, providing a model of possible interactions of ACC, HCO(3)(-), and ascorbate at the active site. In this model, the ACC and bicarbonate binding sites are located close together in the active pocket. HCO(3)(-) is found at hydrogen-bond distance from ACC and interacts (hydrogen bonds or electrostatic interactions) with residues K158, R244, Y162, S246, and R300 of the enzyme. The position of ascorbate is also predicted away from ACC. Individually docked at the active site, the inhibitors ACP and AMEP were found coordinating the metal ion in place of ACC with the phosphonate groups interacting with K158 and R300, thus interlocking with both ACC and bicarbonate binding sites. In conclusion, HCO(3)(-) and ACC together occupy positions similar to the position of 2-oxoglutarate in related enzymes, and through a hydrogen bond HCO(3)(-) likely plays a major role in the stabilization of the substrate in the active pocket.
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Affiliation(s)
- Lydie Brisson
- Aix-Marseille Université and CNRS, Institut des Sciences Moléculaires de Marseille, UMR 7313, Marseille, France
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17
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Sheftel AD, Mason AB, Ponka P. The long history of iron in the Universe and in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1820:161-87. [PMID: 21856378 PMCID: PMC3258305 DOI: 10.1016/j.bbagen.2011.08.002] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2011] [Revised: 07/19/2011] [Accepted: 08/01/2011] [Indexed: 12/21/2022]
Abstract
BACKGROUND Not long after the Big Bang, iron began to play a central role in the Universe and soon became mired in the tangle of biochemistry that is the prima essentia of life. Since life's addiction to iron transcends the oxygenation of the Earth's atmosphere, living things must be protected from the potentially dangerous mix of iron and oxygen. The human being possesses grams of this potentially toxic transition metal, which is shuttling through his oxygen-rich humor. Since long before the birth of modern medicine, the blood-vibrant red from a massive abundance of hemoglobin iron-has been a focus for health experts. SCOPE OF REVIEW We describe the current understanding of iron metabolism, highlight the many important discoveries that accreted this knowledge, and describe the perils of dysfunctional iron handling. GENERAL SIGNIFICANCE Isaac Newton famously penned, "If I have seen further than others, it is by standing upon the shoulders of giants". We hope that this review will inspire future scientists to develop intellectual pursuits by understanding the research and ideas from many remarkable thinkers of the past. MAJOR CONCLUSIONS The history of iron research is a long, rich story with early beginnings, and is far from being finished. This article is part of a Special Issue entitled Transferrins: Molecular mechanisms of iron transport and disorders.
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Affiliation(s)
- Alex D. Sheftel
- University of Ottawa Heart Institute, 40 Ruskin St., Ottawa, ON K1Y 4W7, Canada
| | - Anne B. Mason
- Department of Biochemistry, College of Medicine, University of Vermont, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
| | - Prem Ponka
- Lady Davis Institute for Medical Research, Jewish General Hospital, 3755 Côte-Ste.-Catherine Rd., Montréal, QC H3T 1E2, and Departments of Physiology and Medicine, McGill University, Montréal, QC, Canada
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18
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Guo K, Achilefu S, Berezin MY. Dating bloodstains with fluorescence lifetime measurements. Chemistry 2012; 18:1303-5. [PMID: 22238188 PMCID: PMC3494294 DOI: 10.1002/chem.201102935] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Indexed: 11/09/2022]
Affiliation(s)
- Kevin Guo
- Department of Radiology Washington University School of Medicine, St. Louis, MO (USA), Fax: (+)314-747-5191
| | - Samuel Achilefu
- Department of Radiology Washington University School of Medicine, St. Louis, MO (USA), Fax: (+)314-747-5191
| | - Mikhail Y. Berezin
- Department of Radiology Washington University School of Medicine, St. Louis, MO (USA), Fax: (+)314-747-5191
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Štefl M, James NG, Ross JA, Jameson DM. Applications of phasors to in vitro time-resolved fluorescence measurements. Anal Biochem 2011; 410:62-9. [PMID: 21078290 PMCID: PMC3065364 DOI: 10.1016/j.ab.2010.11.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/05/2010] [Accepted: 11/07/2010] [Indexed: 11/28/2022]
Abstract
The phasor method of treating fluorescence lifetime data provides a facile and convenient approach to characterize lifetime heterogeneity and to detect the presence of excited state reactions such as solvent relaxation and Förster resonance energy transfer. The method uses a plot of M sin(Φ) versus M cos(Φ), where M is the modulation ratio and Φ is the phase angle taken from frequency domain fluorometry. A principal advantage of the phasor method is that it provides a model-less approach to time-resolved data amenable to visual inspection. Although the phasor approach has been recently applied to fluorescence lifetime imaging microscopy, it has not been used extensively for cuvette studies. In the current study, we explore the applications of the method to in vitro samples. The phasors of binary and ternary mixtures of fluorescent dyes demonstrate the utility of the method for investigating complex mixtures. Data from excited state reactions, such as dipolar relaxation in membrane and protein systems and also energy transfer from the tryptophan residue to the chromophore in enhanced green fluorescent protein, are also presented.
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Affiliation(s)
- Martin Štefl
- J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Department of Biophysical Chemistry, Dolejškova 3, Prague 18223, Czech Republic
| | - Nicholas G. James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
| | - Justin A. Ross
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
| | - David M. Jameson
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, 651 Ilalo St., BSB222, Honolulu, Hawaii 96813
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James NG, Ross JA, Stefl M, Jameson DM. Applications of phasor plots to in vitro protein studies. Anal Biochem 2010; 410:70-6. [PMID: 21078289 DOI: 10.1016/j.ab.2010.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/05/2010] [Accepted: 11/07/2010] [Indexed: 10/18/2022]
Abstract
In a recent article, we described the application of phasor analysis to fluorescence intensity decay data on in vitro samples. As detailed in that article, this method provides researchers with a simple graphical method for viewing lifetime data that can be used to quantify individual components of a mixture as well as to identify excited state reactions. In the current article, we extend the use of in vitro phasor analysis to intrinsic protein fluorescence. We show how alterations in the excited state properties of tryptophan residues are easily visualized using the phasor method. Specifically, we demonstrate that protein-ligand and protein-protein interactions can result in unique shifts in the location of phasor points, indicative of protein conformational changes. Application of the method to a rapid kinetic experiment is also shown. Finally, we show that the unfolding of lysozyme with either urea or guanidine hydrochloride results in different phasor trajectories, indicative of unique denaturation pathways.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA
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