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Dušeková E, Garajová K, Yavaşer R, Tomková M, Sedláková D, Dzurillová V, Kulik N, Fadaei F, Shaposhnikova A, Minofar B, Sedlák E. Modulation of global stability, ligand binding and catalytic properties of trypsin by anions. Biophys Chem 2022; 288:106856. [PMID: 35872468 DOI: 10.1016/j.bpc.2022.106856] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 07/02/2022] [Accepted: 07/13/2022] [Indexed: 12/01/2022]
Abstract
Specific salts effect is well-known on stability and solubility of proteins, however, relatively limited knowledge is known regarding the effect on catalytic properties of enzymes. Here, we examined the effect of four sodium anions on thermal stability and catalytic properties of trypsin and binding of the fluorescent probe, p-aminobenzamidine (PAB), to the enzyme. We show that the specific anions effect on trypsin properties agrees with the localization of the anions in the Hofmeister series. Thermal stability of trypsin, Tm, the affinity of the fluorescent probe to the binding site, Kd, and the rate constant, kcat, of trypsin-catalyzed hydrolysis of the substrate N-benzoyl-L-arginine ethyl ester (BAEE) increase with increasing kosmotropic character of anions in the order: perchlorate<bromide<chloride<sulfate, while the value of Michaelis constant, KM, decreases. Correlations between the values of Tm, Kd for PAB, kcat, and KM for BAEE in the presence of 1 M studied salts suggest interrelation among these parameters of the enzyme. Global stabilization as well as increased rigidity of trypsin is accompanied by strengthening of interaction with fluorescent probe PAB and in accordance with decreasing values of KM for the substrate BAEE. Strong correlations between parameters characterizing the trypsin properties with the charge densities of anions clearly indicate direct electrostatic interaction as a basis of the specific anion effect on the conformational and functional properties of the enzyme.
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Affiliation(s)
- Eva Dušeková
- Department of Biophysics, Faculty of Science, P. J. Šafárik University in Košice, Jesenná 5, 04154 Košice, Slovakia
| | - Katarína Garajová
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04154 Košice, Slovakia
| | - Rukiye Yavaşer
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04154 Košice, Slovakia; Chemistry Department, Faculty of Arts and Science, Aydın Adnan Menderes University, 09010 Aydın, Turkey
| | - Mária Tomková
- Center for Interdisciplinary Biosciences, P. J. Šafárik University in Košice, Jesenná 5, 04154 Košice, Slovakia
| | - Dagmar Sedláková
- Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia
| | - Veronika Dzurillová
- Department of Biophysics, Faculty of Science, P. J. Šafárik University in Košice, Jesenná 5, 04154 Košice, Slovakia
| | - Natalia Kulik
- Faculty of Science, University of South Bohemia in České Budějovice, Branišovská 1645/31A, 37005 České Budějovice, Czech Republic
| | - Fatemeh Fadaei
- Faculty of Science, University of South Bohemia in České Budějovice, Branišovská 1645/31A, 37005 České Budějovice, Czech Republic; Laboratory of Structural Biology and Bioinformatics, Institute of Microbiology of the Czech Academy of Sciences, Zámek 136, 37333 Nové Hrady, Czech Republic
| | - Anastasiia Shaposhnikova
- Faculty of Science, University of South Bohemia in České Budějovice, Branišovská 1645/31A, 37005 České Budějovice, Czech Republic; Laboratory of Structural Biology and Bioinformatics, Institute of Microbiology of the Czech Academy of Sciences, Zámek 136, 37333 Nové Hrady, Czech Republic
| | - Babak Minofar
- Laboratory of Structural Biology and Bioinformatics, Institute of Microbiology of the Czech Academy of Sciences, Zámek 136, 37333 Nové Hrady, Czech Republic.
| | - Erik Sedlák
- Center for Interdisciplinary Biosciences, P. J. Šafárik University in Košice, Jesenná 5, 04154 Košice, Slovakia.
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Hernández-Ibáñez N, Montiel V, Gomis-Berenguer A, Ania C, Iniesta J. Effect of confinement of horse heart cytochrome c and formate dehydrogenase from Candida boidinii on mesoporous carbons on their catalytic activity. Bioprocess Biosyst Eng 2021; 44:1699-1710. [PMID: 33813652 PMCID: PMC8238777 DOI: 10.1007/s00449-021-02553-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/12/2021] [Indexed: 12/01/2022]
Abstract
This study reports the immobilization of two biocatalysts (e.g., cytochrome c-Cyt c-and the non-metalloenzyme formate dehydrogenase from Candida boidinii-cbFDH) on a series of mesoporous carbons with controlled pore sizes. The catalytic activity of the nanoconfined proteins was correlated with the pore size distribution of the carbon materials used as supports. The electrochemical behaviour of nanoconfined Cyt c showed direct electron transfer electroactivity in pore sizes matching tightly the protein dimension. The pseudo-peroxidase activity towards H2O2 reduction was enhanced at pH 4.0, due to the protein conformational changes. For cbFDH, the reduction of CO2 towards formic acid was evaluated for the nanoconfined protein, in the presence of nicotinamide adenine dinucleotide (NADH). The carbons displayed different cbFDH uptake capacity, governed by the dimensions of the main mesopore cavities and their accessibility through narrow pore necks. The catalytic activity of nanoconfined cbFDH was largely improved, compared to its performance in free solution. Regardless of the carbon support used, the production of formic acid was higher upon immobilization with lower nominal cbFDH:NADH ratios.
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Affiliation(s)
- Naiara Hernández-Ibáñez
- Physical Chemistry Department and Institute of Electrochemistry, University of Alicante, 03080, Alicante, Spain
| | - Vicente Montiel
- Physical Chemistry Department and Institute of Electrochemistry, University of Alicante, 03080, Alicante, Spain
| | - Alicia Gomis-Berenguer
- CEMHTI, CNRS (UPR 3079) University of Orléans, 45071, Orléans, France.,Department of Chemistry, School of Engineering Science in Chemistry, Biochemistry and Health, Royal Institute of Technology, KTH, Teknikringen 30, SE-100 44, Stockholm, Sweden
| | - Conchi Ania
- INCAR, CSIC, Apdo 26, 33011, Oviedo, Spain. .,CEMHTI, CNRS (UPR 3079) University of Orléans, 45071, Orléans, France.
| | - Jesús Iniesta
- Physical Chemistry Department and Institute of Electrochemistry, University of Alicante, 03080, Alicante, Spain.
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Sedlák E, Žár T, Varhač R, Musatov A, Tomášková N. Anion-Specific Effects on the Alkaline State of Cytochrome c. BIOCHEMISTRY (MOSCOW) 2021; 86:59-73. [PMID: 33705282 DOI: 10.1134/s0006297921010065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Specific effects of anions on the structure, thermal stability, and peroxidase activity of native (state III) and alkaline (state IV) cytochrome c (cyt c) have been studied by the UV-VIS absorbance spectroscopy, intrinsic tryptophan fluorescence, and circular dichroism. Thermal and isothermal denaturation monitored by the tryptophan fluorescence and circular dichroism, respectively, implied lower stability of cyt c state IV in comparison with the state III. The pKa value of alkaline isomerization of cyt c depended on the present salts, i.e., kosmotropic anions increased and chaotropic anions decreased pKa (Hofmeister effect on protein stability). The peroxidase activity of cyt c in the state III, measured by oxidation of guaiacol, showed clear dependence on the salt position in the Hofmeister series, while cyt c in the alkaline state lacked the peroxidase activity regardless of the type of anions present in the solution. The alkaline isomerization of cyt c in the presence of 8 M urea, measured by Trp59 fluorescence, implied an existence of a high-affinity non-native ligand for the heme iron even in a partially denatured protein conformation. The conformation of the cyt c alkaline state in 8 M urea was considerably modulated by the specific effect of anions. Based on the Trp59 fluorescence quenching upon titration to alkaline pH in 8 M urea and molecular dynamics simulation, we hypothesize that the Lys79 conformer is most likely the predominant alkaline conformer of cyt c. The high affinity of the sixth ligand for the heme iron is likely a reason of the lack of peroxidase activity of cyt c in the alkaline state.
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Affiliation(s)
- Erik Sedlák
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Košice, 04154, Slovakia. .,Centre for Interdisciplinary Biosciences, P. J. Šafárik University in Košice, Košice, 04154, Slovakia
| | - Tibor Žár
- Centre for Interdisciplinary Biosciences, P. J. Šafárik University in Košice, Košice, 04154, Slovakia.
| | - Rastislav Varhač
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Košice, 04154, Slovakia.
| | - Andrej Musatov
- Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Košice, 040 01, Slovakia.
| | - Nataša Tomášková
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Košice, 04154, Slovakia.
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Garajová K, Sedláková D, Berta M, Gazova Z, Sedlák E. Destabilization effect of imidazolium cation-Hofmeister anion salts on cytochrome c. Int J Biol Macromol 2020; 164:3808-3813. [DOI: 10.1016/j.ijbiomac.2020.09.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/24/2020] [Accepted: 09/02/2020] [Indexed: 01/15/2023]
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Effect of imidazolium based ionic liquids on CO-association dynamics and thermodynamic stability of Ferrocytochrome c. Biophys Chem 2020; 268:106497. [PMID: 33212391 DOI: 10.1016/j.bpc.2020.106497] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 11/01/2020] [Accepted: 11/01/2020] [Indexed: 11/20/2022]
Abstract
Analysis of kinetic and thermodynamic parameters measured for CO-association reaction of Ferrocytochrome c (Ferrocyt c) under variable concentrations of 1-butyl-3-methylimidazolium with varying anion ([Bmim]X) (X = Cl-, I-, Br-, HSO4-) at pH 7 revealed that the low concentration of [Bmim]X (≤0.5 M) constrains the CO-association dynamics of Ferrocyt c and typically follows the order: [Bmim]HSO4 > [Bmim]Cl > [Bmim]Br > [Bmim]I. At relatively higher concentrations (>0.5), the chaotropic action of [Bmim]+ dominates which consequently increases the thermal-fluctuations responsible to denature the protein and thus accelerates the speed of CO-association reaction. Analysis of thermal denaturation curves of Ferrocyt c measured at different concentrations of [Bmim]X revealed that the [Bmim]X decreases the thermodynamic stability of protein and typically follows the order: [Bmim]I > [Bmim]Br > [Bmim]Cl > [Bmim]CH3COO > [Bmim]HSO4, demonstrating that the effect of [Bmim]X on thermodynamic stability of protein is not in accordance to Hofmeister series effect of anions because instead of increasing the kosmotropic anion carrying [Bmim]X ([Bmim]CH3COO and [Bmim]HSO4) also decreases the thermodynamic stability of protein.
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Sedlák E, Sedláková D, Marek J, Hančár J, Garajová K, Žoldák G. Ion-Specific Protein/Water Interface Determines the Hofmeister Effect on the Kinetic Stability of Glucose Oxidase. J Phys Chem B 2019; 123:7965-7973. [DOI: 10.1021/acs.jpcb.9b05195] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Erik Sedlák
- Center for Interdisciplinary Biosciences, Technology and Innovation Park P.J. Šafárik University, Jesenna 5, 041 54 Košice, Slovakia
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04001 Košice, Slovakia
| | - Dagmar Sedláková
- Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, Slovakia
| | - Jozef Marek
- Department of Biophysics, Institute of Experimental Physics, Slovak Academy of Sciences, Watsonova 47, 04001 Košice, Slovakia
| | - Jozef Hančár
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04001 Košice, Slovakia
| | - Katarína Garajová
- Department of Biochemistry, Faculty of Science, P. J. Šafárik University in Košice, Moyzesova 11, 04001 Košice, Slovakia
| | - Gabriel Žoldák
- Center for Interdisciplinary Biosciences, Technology and Innovation Park P.J. Šafárik University, Jesenna 5, 041 54 Košice, Slovakia
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Dušeková E, Garajová K, Yavaşer R, Varhač R, Sedlák E. Hofmeister effect on catalytic properties of chymotrypsin is substrate-dependent. Biophys Chem 2018; 243:8-16. [DOI: 10.1016/j.bpc.2018.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 09/30/2018] [Accepted: 10/09/2018] [Indexed: 12/26/2022]
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Tomášková N, Varhač R, Lysáková V, Musatov A, Sedlák E. Peroxidase activity of cytochrome c in its compact state depends on dynamics of the heme region. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1866:1073-1083. [DOI: 10.1016/j.bbapap.2018.09.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 09/06/2018] [Accepted: 09/10/2018] [Indexed: 10/28/2022]
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Effects of lyotropic anions on thermodynamic stability and dynamics of horse cytochrome c. Biophys Chem 2018; 240:88-97. [DOI: 10.1016/j.bpc.2018.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Revised: 06/09/2018] [Accepted: 06/10/2018] [Indexed: 11/19/2022]
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Garajová K, Balogová A, Dušeková E, Sedláková D, Sedlák E, Varhač R. Correlation of lysozyme activity and stability in the presence of Hofmeister series anions. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1865:281-288. [DOI: 10.1016/j.bbapap.2016.11.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 11/01/2016] [Accepted: 11/28/2016] [Indexed: 01/01/2023]
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Lang J, Cayir M, Walg SP, Di Martino-Fumo P, Thiel WR, Niedner-Schatteburg G. Intermetallic Competition in the Fragmentation of Trimetallic Au-Zn-Alkali Complexes. Chemistry 2016; 22:2345-55. [PMID: 26785330 DOI: 10.1002/chem.201504093] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Indexed: 12/20/2022]
Affiliation(s)
- Johannes Lang
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
| | - Merve Cayir
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
| | - Simon P. Walg
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
| | - Patrick Di Martino-Fumo
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
| | - Werner R. Thiel
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
| | - Gereon Niedner-Schatteburg
- Fachbereich Chemie and Forschungszentrum OPTIMAS; Technische Universität Kaiserslautern; 67663 Kaiserslautern Germany
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Varhač R, Sedláková D, Stupák M, Sedlák E. Non-two-state thermal denaturation of ferricytochrome c at neutral and slightly acidic pH values. Biophys Chem 2015; 203-204:41-50. [DOI: 10.1016/j.bpc.2015.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 05/08/2015] [Accepted: 05/11/2015] [Indexed: 12/19/2022]
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Varhač R. Urea-induced modification of cytochrome c flexibility as probed by cyanide binding. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:739-44. [DOI: 10.1016/j.bbapap.2013.01.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Revised: 01/08/2013] [Accepted: 01/09/2013] [Indexed: 11/25/2022]
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Yang Z, Liu XJ, Chen C, Halling PJ. Hofmeister effects on activity and stability of alkaline phosphatase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1804:821-8. [PMID: 20025997 DOI: 10.1016/j.bbapap.2009.12.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/01/2009] [Accepted: 12/08/2009] [Indexed: 11/30/2022]
Abstract
We have studied the effects on alkaline phosphatase of adding high concentrations (normally 1.0 M) of simple salts. It is necessary to allow for significant effects of salts on the extinction coefficient of the reaction product, and on the apparent pH of the buffer. Both activity and stability of the enzyme correlate well with the Hofmeister series in terms of the salt's kosmotropic/chaotropic properties, which are assessed by the Jones-Dole viscosity B coefficients (B(+) for cations and B(-) for anions). The catalytic activity or V(max)/K(m) of the enzyme showed a bell-shaped relationship with the (B(-)-B(+)) values of the salts present, being optimal with salts (such as NaCl, KCl, and KNO(3)) where the anion and cation have similar kosmotropic/chaotropic properties. This effect is believed to be enzyme-specific and relates to the impact of both cations and anions on the enzyme's surface pH, active site, and catalytic mechanism. Anions play a more predominant role than cations in affecting enzyme stability. The rate of irreversible thermal inactivation is strongly reduced by addition of kosmotropic anions like SO(4)(2-) (half-life increased from 8 to 580 min at 60 degrees C). This effect is general and the mechanism probably involves the ability of the ions to affect the water solvation layer around the enzyme molecule and to interact with both the surface and internal structure of the enzyme.
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Affiliation(s)
- Zhen Yang
- College of life sciences, Shenzhen University, Shenzhen 518060, Guangdong, China 518060.
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Yang Z. Hofmeister effects: an explanation for the impact of ionic liquids on biocatalysis. J Biotechnol 2009; 144:12-22. [DOI: 10.1016/j.jbiotec.2009.04.011] [Citation(s) in RCA: 315] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 04/07/2009] [Accepted: 04/20/2009] [Indexed: 12/01/2022]
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Varhač R, Tomášková N, Fabián M, Sedlák E. Kinetics of cyanide binding as a probe of local stability/flexibility of cytochrome c. Biophys Chem 2009; 144:21-6. [DOI: 10.1016/j.bpc.2009.06.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2009] [Revised: 05/30/2009] [Accepted: 06/01/2009] [Indexed: 10/20/2022]
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Valušová E, Švec P, Antalík M. Structural and thermodynamic behavior of cytochrome c assembled with glutathione-covered gold nanoparticles. J Biol Inorg Chem 2009; 14:621-30. [DOI: 10.1007/s00775-009-0476-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 01/24/2009] [Indexed: 12/01/2022]
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Effect of Hofmeister ions on protein thermal stability: Roles of ion hydration and peptide groups? Arch Biochem Biophys 2008; 479:69-73. [DOI: 10.1016/j.abb.2008.08.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Revised: 08/17/2008] [Accepted: 08/20/2008] [Indexed: 11/22/2022]
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Varhač R, Antalík M. Correlation of acid-induced conformational transition of ferricytochrome c with cyanide binding kinetics. J Biol Inorg Chem 2008; 13:713-21. [DOI: 10.1007/s00775-008-0357-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Accepted: 02/16/2008] [Indexed: 10/22/2022]
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Tóth K, Sedlák E, Sprinzl M, Zoldák G. Flexibility and enzyme activity of NADH oxidase from Thermus thermophilus in the presence of monovalent cations of Hofmeister series. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1784:789-95. [PMID: 18339331 DOI: 10.1016/j.bbapap.2008.01.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 01/26/2008] [Accepted: 01/29/2008] [Indexed: 11/25/2022]
Abstract
Recently, we have shown that anions of Hofmeister series affect the enzyme activity through modulation of flexibility of its active site. The enzyme activity vs. anion position in Hofmeister series showed an unusual bell-shaped dependence. In the present work, six monovalent cations (Na(+), Gdm(+), NH(4)(+), Li(+), K(+) and Cs(+)) of Hofmeister series with chloride as a counterion have been studied in relation to activity and stability of flavoprotein NADH oxidase from Thermus thermophilus (NOX). With the exception of strongly chaotropic guanidinium cation, cations are significantly less effective in promoting the Hofmeister effect than anions mainly due to repulsive interactions of positive charges around the active site. Thermal denaturations of NOX reveal unfavorable electrostatic interaction at the protein surface that may be shielded to different extent by salts. Michaelis-Menten constants for NADH, accessibility of the active site as reflected by Stern-Volmer constants and activity of NOX at high cation concentrations (1-2 M) show bell-shaped dependences on cation position in Hofmeister series. Our analysis indicates that in the presence of kosmotropic cations the enzyme is more stable and possibly more rigid than in the presence of chaotropic cations. Molecular dynamic (MD) simulations of NOX showed that active site switches between open and closed conformations [J. Hritz, G. Zoldak, E. Sedlak, Cofactor assisted gating mechanism in the active site of NADH oxidase from Thermus thermophilus, Proteins 64 (2006) 465-476]. Enzyme activity, as well as substrate binding, can be regulated by the salt mediated perturbation of the balance between open and closed forms. We propose that compensating effect of accessibility and flexibility of the enzyme active site leads to bell-shaped dependence of the investigated parameters.
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Affiliation(s)
- Kamil Tóth
- Department of Biochemistry, Faculty of Sciences P. J. Safárik University, Kosice, Slovakia
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