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The Role of Metal Ions in the Electron Transport through Azurin-Based Junctions. APPLIED SCIENCES-BASEL 2021. [DOI: 10.3390/app11093732] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We studied the coherent electron transport through metal–protein–metal junctions based on a blue copper azurin, in which the copper ion was replaced by three different metal ions (Co, Ni and Zn). Our results show that neither the protein structure nor the transmission at the Fermi level change significantly upon metal replacement. The discrepancy with previous experimental observations suggests that the transport mechanism taking place in these types of junctions is probably not fully coherent.
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De novo biosynthesis of a nonnatural cobalt porphyrin cofactor in E. coli and incorporation into hemoproteins. Proc Natl Acad Sci U S A 2021; 118:2017625118. [PMID: 33850014 DOI: 10.1073/pnas.2017625118] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Enzymes that bear a nonnative or artificially introduced metal center can engender novel reactivity and enable new spectroscopic and structural studies. In the case of metal-organic cofactors, such as metalloporphyrins, no general methods exist to build and incorporate new-to-nature cofactor analogs in vivo. We report here that a common laboratory strain, Escherichia coli BL21(DE3), biosynthesizes cobalt protoporphyrin IX (CoPPIX) under iron-limited, cobalt-rich growth conditions. In supplemented minimal media containing CoCl2, the metabolically produced CoPPIX is directly incorporated into multiple hemoproteins in place of native heme b (FePPIX). Five cobalt-substituted proteins were successfully expressed with this new-to-nature cobalt porphyrin cofactor: myoglobin H64V V68A, dye decolorizing peroxidase, aldoxime dehydratase, cytochrome P450 119, and catalase. We show conclusively that these proteins incorporate CoPPIX, with the CoPPIX making up at least 95% of the total porphyrin content. In cases in which the native metal ligand is a sulfur or nitrogen, spectroscopic parameters are consistent with retention of native metal ligands. This method is an improvement on previous approaches with respect to both yield and ease-of-implementation. Significantly, this method overcomes a long-standing challenge to incorporate nonnatural cofactors through de novo biosynthesis. By utilizing a ubiquitous laboratory strain, this process will facilitate spectroscopic studies and the development of enzymes for CoPPIX-mediated biocatalysis.
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Amdursky N, Sepunaru L, Raichlin S, Pecht I, Sheves M, Cahen D. Electron Transfer Proteins as Electronic Conductors: Significance of the Metal and Its Binding Site in the Blue Cu Protein, Azurin. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2015; 2:1400026. [PMID: 27980928 PMCID: PMC5115354 DOI: 10.1002/advs.201400026] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 02/08/2015] [Indexed: 05/07/2023]
Abstract
Electron transfer (ET) proteins are biomolecules with specific functions, selected by evolution. As such they are attractive candidates for use in potential bioelectronic devices. The blue copper protein azurin (Az) is one of the most-studied ET proteins. Traditional spectroscopic, electrochemical, and kinetic methods employed for studying ET to/from the protein's Cu ion have been complemented more recently by studies of electrical conduction through a monolayer of Az in the solid-state, sandwiched between electrodes. As the latter type of measurement does not require involvement of a redox process, it also allows monitoring electronic transport (ETp) via redox-inactive Az-derivatives. Here, results of macroscopic ETp via redox-active and -inactive Az derivatives, i.e., Cu(II) and Cu(I)-Az, apo-Az, Co(II)-Az, Ni(II)-Az, and Zn(II)-Az are reported and compared. It is found that earlier reported temperature independence of ETp via Cu(II)-Az (from 20 K until denaturation) is unique, as ETp via all other derivatives is thermally activated at temperatures >≈200 K. Conduction via Cu(I)-Az shows unexpected temperature dependence >≈200 K, with currents decreasing at positive and increasing at negative bias. Taking all the data together we find a clear compensation effect of Az conduction around the Az denaturation temperature. This compensation can be understood by viewing the Az binding site as an electron trap, unless occupied by Cu(II), as in the native protein, with conduction of the native protein setting the upper transport efficiency limit.
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Affiliation(s)
- Nadav Amdursky
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel; Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - Lior Sepunaru
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel
| | - Sara Raichlin
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel; Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - Israel Pecht
- Departments of Immunology Weizmann Institute of Science Rehovot 76100 Israel
| | - Mordechai Sheves
- Departments of Organic Chemistry Weizmann Institute of Science Rehovot 76100 Israel
| | - David Cahen
- Departments of Materials and Interfaces Weizmann Institute of Science Rehovot 76100 Israel
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Zampino AP, Masters FM, Bladholm EL, Panzner MJ, Berry SM, Leeper TC, Ziegler CJ. Mercury metallation of the copper protein azurin and structural insight into possible heavy metal reactivity. J Inorg Biochem 2014; 141:152-160. [DOI: 10.1016/j.jinorgbio.2014.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 09/05/2014] [Accepted: 09/05/2014] [Indexed: 01/17/2023]
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6
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Sahu C, Sen K, Pakhira S, Mondal B, Das AK. Binding affinity of substituted ureido-benzenesulfonamide ligands to the carbonic anhydrase receptor: a theoretical study of enzyme inhibition. J Comput Chem 2013; 34:1907-16. [PMID: 23712937 DOI: 10.1002/jcc.23335] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 04/25/2013] [Accepted: 04/26/2013] [Indexed: 01/23/2023]
Abstract
The binding properties of a series of benzenesulfonamide inhibitors (4-substituted-ureido-benzenesulfonamides, UBSAs) of human carbonic anhydrase II (hCA II) enzyme with active site residues have been studied using a hybrid quantum mechanical/molecular mechanical (QM/MM) model. To account for the important docking interactions between the UBSAs ligand and hCA II enzyme, a molecular docking program AutoDock Vina is used. The molecular docking results obtained by AutoDock Vina revealed that the docked conformer has root mean square deviation value less than 1.50 Å compared to X-ray crystal structures. The inhibitory activity of UBSA ligands against hCA II is found to be in good agreement with the experimental results. The thermodynamic parameters for inhibitor binding show that hydrogen bonding, hydrophilic, and hydrophobic interactions play a major role in explaining the diverse inhibitory range of these derivatives. Additionally, natural bond orbital analysis is performed to characterize the ligand-metal charge transfer stability. The insights gained from this study have great potential to design new hCA-II inhibitor, 4-[3-(1-p-Tolyl-4-trifluoromethyl-1H-pyrazol-3-yl)-ureido]-benzenesulfonamide, which belongs to the family of UBSA inhibitors and shows similar type of inhibitor potency with hCA II. This work also reveals that a QM/MM model and molecular docking method are computationally feasible and accurate for studying substrate-protein inhibition.
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Affiliation(s)
- Chandan Sahu
- Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700032, India
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7
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Isomorphic deactivation of a Pseudomonas aeruginosa oxidoreductase: The crystal structure of Ag(I) metallated azurin at 1.7 Å. J Inorg Biochem 2013; 128:11-6. [PMID: 23911566 DOI: 10.1016/j.jinorgbio.2013.07.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Revised: 07/05/2013] [Accepted: 07/08/2013] [Indexed: 11/21/2022]
Abstract
Multiple biophysical methods demonstrate that silver effectively metallates Pseudomonas aeruginosa apo-azurin in solution. X-ray crystallography of the silver-modified protein reveals that silver binds to azurin at the traditional copper mediated active site with nearly identical geometry. Cyclic voltammetry indicates that the silver adduct is redox inert. Our results suggest that a potential mechanism for the microbial toxicity of silver is the deactivation of copper oxidoreductases by the effective binding and structural mimicry by silver without the corresponding function.
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Davydov RM, McLaughlin MP, Bill E, Hoffman BM, Holland PL. Generation of high-spin iron(I) in a protein environment using cryoreduction. Inorg Chem 2013; 52:7323-5. [PMID: 24004284 DOI: 10.1021/ic4011339] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
High-spin Fe(1+) sites are potentially important in iron-sulfur proteins but are rare in synthetic compounds and unknown in metalloproteins. Here, we demonstrate a spectroscopically characterized example of high-spin non-heme Fe(1+) in a protein environment. Cryoreduction of Fe(2+)-substituted azurin at 77 K with (60)Co γ radiation generates a new species with a S = (3)/2 (high-spin) Fe(1+) center having D > 0 and E/D ~ 0.25. This transient species is stable in a glycerol-water glass only up to ~170 K. A combination of electron paramagnetic resonance and Mössbauer spectroscopies provides a powerful means of identifying a transient high-spin Fe(1+) site in a protein scaffold.
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Affiliation(s)
- Roman M Davydov
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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9
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McLaughlin MP, Retegan M, Bill E, Payne TM, Shafaat HS, Peña S, Sudhamsu J, Ensign AA, Crane BR, Neese F, Holland PL. Azurin as a protein scaffold for a low-coordinate nonheme iron site with a small-molecule binding pocket. J Am Chem Soc 2012; 134:19746-57. [PMID: 23167247 PMCID: PMC3515693 DOI: 10.1021/ja308346b] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The apoprotein of Pseudomonas aeruginosa azurin binds iron(II) to give a 1:1 complex, which has been characterized by electronic absorption, Mössbauer, and NMR spectroscopies, as well as X-ray crystallography and quantum-chemical computations. Despite potential competition by water and other coordinating residues, iron(II) binds tightly to the low-coordinate site. The iron(II) complex does not react with chemical redox agents to undergo oxidation or reduction. Spectroscopically calibrated quantum-chemical computations show that the complex has high-spin iron(II) in a pseudotetrahedral coordination environment, which features interactions with side chains of two histidines and a cysteine as well as the C═O of Gly45. In the (5)A(1) ground state, the d(z(2)) orbital is doubly occupied. Mutation of Met121 to Ala leaves the metal site in a similar environment but creates a pocket for reversible binding of small anions to the iron(II) center. Specifically, azide forms a high-spin iron(II) complex and cyanide forms a low-spin iron(II) complex.
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Affiliation(s)
| | - Marius Retegan
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Thomas M. Payne
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
| | - Hannah S. Shafaat
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Salvador Peña
- Department of Chemistry, University of Rochester, Rochester, New York 14618
| | - Jawahar Sudhamsu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
| | - Amy A. Ensign
- Department of Chemistry, University of Rochester, Rochester, New York 14618
| | - Brian R. Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853
| | - Frank Neese
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, New York 14618
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Warren JJ, Lancaster KM, Richards JH, Gray HB. Inner- and outer-sphere metal coordination in blue copper proteins. J Inorg Biochem 2012; 115:119-26. [PMID: 22658756 PMCID: PMC3434318 DOI: 10.1016/j.jinorgbio.2012.05.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2012] [Revised: 04/30/2012] [Accepted: 05/01/2012] [Indexed: 10/28/2022]
Abstract
Blue copper proteins (BCPs) comprise classic cases of Nature's profound control over the electronic structures and chemical reactivity of transition metal ions. Early studies of BCPs focused on their inner coordination spheres, that is, residues that directly coordinate Cu. Equally important are the electronic and geometric perturbations to these ligands provided by the outer coordination sphere. In this tribute to Hans Freeman, we review investigations that have advanced the understanding of how inner-sphere and outer-sphere coordination affects biological Cu properties.
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Affiliation(s)
- Jeffrey J Warren
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA
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11
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Zheng AX, Si J, Tang XY, Miao LL, Yu M, Hou KP, Wang F, Li HX, Lang JP. Reactions of the Cationic Zinc Thiolate Model Complex [Zn(Tab)4](PF6)2 with N-Donor Ligands and Cobalt Dichloride. Inorg Chem 2012; 51:10262-73. [DOI: 10.1021/ic301191n] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ai-Xia Zheng
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
- State
Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai 210093, People’s Republic of China
| | - Jing Si
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Xiao-Yan Tang
- Jiangsu Laboratory of Advanced Functional Materials, Changshu Institute of Technology, Changshu 215500,
People’s Republic of China
| | - Li-Li Miao
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Miao Yu
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Kai-Peng Hou
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Fan Wang
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Hong-Xi Li
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
| | - Jian-Ping Lang
- College of
Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, People’s
Republic of China
- State
Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai 210093, People’s Republic of China
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12
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McLaughlin MP, Darrah TH, Holland PL. Palladium(II) and platinum(II) bind strongly to an engineered blue copper protein. Inorg Chem 2011; 50:11294-6. [PMID: 22026434 DOI: 10.1021/ic2017648] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Studies of palladium(II) and platinum(II) binding to well-characterized proteins contribute to understanding the influence of these metals in the environment and body. The well-characterized apoprotein of azurin has a soft-metal binding site that may be exposed to solvent by mutation of a coordinating His-117 residue to glycine (H117G). Palladium(II) and platinum(II) form strong 1:1 adducts with the apo form of H117G azurin. A combination of UV-vis, circular dichroism, and inductively coupled plasma mass spectrometry techniques suggests that the metal binds specifically at His-46 and Cys-112 of the protein.
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Affiliation(s)
- Matthew P McLaughlin
- Department of Chemistry, University of Rochester, Rochester, New York 14618, United States
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13
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Lee T, Min J, Kim SU, Choi JW. Multifunctional 4-bit biomemory chip consisting of recombinant azurin variants. Biomaterials 2011; 32:3815-21. [DOI: 10.1016/j.biomaterials.2011.01.072] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Accepted: 01/30/2011] [Indexed: 10/18/2022]
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14
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Gessmann R, Kyvelidou C, Papadovasilaki M, Petratos K. The crystal structure of cobalt-substituted pseudoazurin from Alcaligenes faecalis. Biopolymers 2010; 95:202-7. [DOI: 10.1002/bip.21553] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Rajapandian V, Hakkim V, Subramanian V. Molecular Dynamics Studies on Native, Loop-Contracted, and Metal Ion-Substituted Azurins. J Phys Chem B 2010; 114:8474-86. [DOI: 10.1021/jp911301v] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- V. Rajapandian
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
| | - V. Hakkim
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
| | - V. Subramanian
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
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Rajapandian V, Raman SS, Hakkim V, Parthasarathi R, Subramanian V. Molecular mechanics and molecular dynamics study on azurin using extensible and systematic force field (ESFF). ACTA ACUST UNITED AC 2009. [DOI: 10.1016/j.theochem.2009.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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17
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Rajapandian V, Hakkim V, Subramanian V. ONIOM Calculation on Azurin: Effect of Metal Ion Substitutions. J Phys Chem A 2009; 113:8615-25. [DOI: 10.1021/jp900451f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- V. Rajapandian
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
| | - V. Hakkim
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
| | - V. Subramanian
- Chemical Laboratory, Central Leather Research Institute, Council of Scientific and Industrial Research, Adyar, Chennai 600 020, India
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Sato K, Firbank S, Li C, Banfield M, Dennison C. The Importance of the Long Type 1 Copper‐Binding Loop of Nitrite Reductase for Structure and Function. Chemistry 2008; 14:5820-8. [DOI: 10.1002/chem.200701997] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Gavel OY, Bursakov SA, Di Rocco G, Trincão J, Pickering IJ, George GN, Calvete JJ, Shnyrov VL, Brondino CD, Pereira AS, Lampreia J, Tavares P, Moura JJG, Moura I. A new type of metal-binding site in cobalt- and zinc-containing adenylate kinases isolated from sulfate-reducers Desulfovibrio gigas and Desulfovibrio desulfuricans ATCC 27774. J Inorg Biochem 2008; 102:1380-95. [PMID: 18328566 DOI: 10.1016/j.jinorgbio.2008.01.023] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Revised: 01/13/2008] [Accepted: 01/18/2008] [Indexed: 11/28/2022]
Abstract
Adenylate kinase (AK) mediates the reversible transfer of phosphate groups between the adenylate nucleotides and contributes to the maintenance of their constant cellular level, necessary for energy metabolism and nucleic acid synthesis. The AK were purified from crude extracts of two sulfate-reducing bacteria (SRB), Desulfovibrio (D.) gigas NCIB 9332 and Desulfovibrio desulfuricans ATCC 27774, and biochemically and spectroscopically characterised in the native and fully cobalt- or zinc-substituted forms. These are the first reported adenylate kinases that bind either zinc or cobalt and are related to the subgroup of metal-containing AK found, in most cases, in Gram-positive bacteria. The electronic absorption spectrum is consistent with tetrahedral coordinated cobalt, predominantly via sulfur ligands, and is supported by EPR. The involvement of three cysteines in cobalt or zinc coordination was confirmed by chemical methods. Extended X-ray absorption fine structure (EXAFS) indicate that cobalt or zinc are bound by three cysteine residues and one histidine in the metal-binding site of the "LID" domain. The sequence 129Cys-X5-His-X15-Cys-X2-Cys of the AK from D. gigas is involved in metal coordination and represents a new type of binding motif that differs from other known zinc-binding sites of AK. Cobalt and zinc play a structural role in stabilizing the LID domain.
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Affiliation(s)
- Olga Yu Gavel
- REQUIMTE, Departamento de Química, Centro de Química Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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Riley EA, Petros AK, Smith KA, Gibney BR, Tierney DL. Frequency-switching inversion-recovery for severely hyperfine-shifted NMR: evidence of asymmetric electron relaxation in high-spin Co(II). Inorg Chem 2007; 45:10016-8. [PMID: 17140197 DOI: 10.1021/ic061207h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new method for reliably measuring longitudinal relaxation rates for severely hyperfine-shifted NMR signals in aqueous solutions is presented. The method is illustrated for a well-defined cobalt tetracysteinate, with relevance to cobalt-substituted metalloproteins. The relaxation measurements are indicative of asymmetric electronic relaxation of the high-spin Co(II) ion.
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Affiliation(s)
- Erin A Riley
- Department of Chemistry, University of New Mexico, Albuquerque, New Mexico 87131, USA
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Rosa V, Gonzalez PJ, Avilés T, Gomes PT, Welter R, Rizzi AC, Passeggi MCG, Brondino CD. Synthesis, Solid-State Structures, and EPR Spectroscopic Studies on Polycrystalline and Single-Crystal Samples of α-Diimine Cobalt(II) Complexes. Eur J Inorg Chem 2006. [DOI: 10.1002/ejic.200600448] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
Metal-thiolate active sites play major roles in bioinorganic chemistry. The M--S(thiolate) bonds can be very covalent, and involve different orbital interactions. Spectroscopic features of these active sites (intense, low-energy charge transfer transitions) reflect the high covalency of the M--S(thiolate) bonds. The energy of the metal-thiolate bond is fairly insensitive to its ionic/covalent and pi/sigma nature as increasing M--S covalency reduces the charge distribution, hence the ionic term, and these contributions can compensate. Thus, trends observed in stability constants (i.e., the Irving-Williams series) mostly reflect the dominantly ionic contribution to bonding of the innocent ligand being replaced by the thiolate. Due to high effective nuclear charges of the Cu(II) and Fe(III) ions, the cupric- and ferric-thiolate bonds are very covalent, with the former having strong pi and the latter having more sigma character. For the blue copper site, the high pi covalency couples the metal ion into the protein for rapid directional long range electron transfer. For rubredoxins, because the redox active molecular orbital is pi in nature, electron transfer tends to be more localized in the vicinity of the active site. Although the energy of hydrogen bonding of the protein environment to the thiolate ligands tends to be fairly small, H-bonding can significantly affect the covalency of the metal-thiolate bond and contribute to redox tuning by the protein environment.
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Affiliation(s)
- Edward I Solomon
- Department of Chemistry, Stanford University, 333 Campus Drive, Stanford, California 94305, USA.
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Czernuszewicz RS, Fraczkiewicz G, Zareba AA. A detailed resonance Raman spectrum of Nickel(II)-substituted Pseudomonas aeruginosa azurin. Inorg Chem 2005; 44:5745-52. [PMID: 16060626 DOI: 10.1021/ic050553g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nickel(II) and cobalt(II) derivatives of the blue copper protein Pseudomonas aeruginosa azurin have been studied by resonance Raman (RR) spectroscopy at liquid-nitrogen temperatures. Vibrational assignments for the observed RR bands of Ni(II)-azurin have been made through a study of (62)Ni-substituted azurin. A comparison of Ni(II)-azurin RR spectra with those of the wild type (Cu-containing) protein showed Ni(II)-S(Cys) stretching vibrations, nu(Ni-S)(Cys), at substantially lower frequencies (approximately 360 versus approximately 400 cm(-1), respectively), indicating that the Ni(II)-S(Cys) bond is much weaker than the corresponding Cu(II)-S(Cys) bond. Resonance enhanced predominantly nu(Ni-N)(His) modes indicate that the metal-N(His) bond distances in the Ni(II) derivative are the same as those in native azurin. The vibrational data also confirm a tetrahedral disposition of ligands about the metal in Ni(II)-azurin found in the protein crystallographic structures. As expected, excitation profile measurements on Ni(II)-azurin show that the nu(Ni-S)(Cys) assignable modes give maxima at the 440-nm absorption band, which confirms a S(Cys) --> Ni(II) charge-transfer origin of the 440-nm electronic transition in Ni(II)-substituted azurin.
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Gorelsky SI, Basumallick L, Vura-Weis J, Sarangi R, Hodgson KO, Hedman B, Fujisawa K, Solomon EI. Spectroscopic and DFT investigation of [M{HB(3,5-iPr2pz)3}(SC6F5)] (M = Mn, Fe, Co, Ni, Cu, and Zn) model complexes: periodic trends in metal-thiolate bonding. Inorg Chem 2005; 44:4947-60. [PMID: 15998022 PMCID: PMC2593087 DOI: 10.1021/ic050371m] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A series of metal-varied [ML(SC6F5)] model complexes (where L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate and M = Mn, Fe, Co, Ni, Cu, and Zn) related to blue copper proteins has been studied by a combination of absorption, MCD, resonance Raman, and S K-edge X-ray absorption spectroscopies. Density functional calculations have been used to characterize these complexes and calculate their spectra. The observed variations in geometry, spectra, and bond energies are interpreted in terms of changes in the nature of metal-ligand bonding interactions. The metal 3d-ligand orbital interaction, which contributes to covalent bonding in these complexes, becomes stronger going from Mn(II) to Co(II) (the sigma contribution) and to Cu(II) (the pi contribution). This change in the covalency results from the increased effective nuclear charge of the metal atom in going from Mn(II) to Zn(II) and the change in the 3d orbital populations (d5-->d10). Ionic bonding also plays an important role in determining the overall strength of the ML(+)-SC6F5(-) interaction. However, there is a compensating effect: as the covalent contribution to the metal-ligand bonding increases, the ionic contribution decreases. These results provide insight into the Irving-Williams series, where it is found that the bonding of the ligand being replaced by the thiolate makes a major contribution to the observed order of the stability constants over the series of metal ions.
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Affiliation(s)
| | | | - Josh Vura-Weis
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | | | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309
| | - Britt Hedman
- Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94309
| | - Kiyoshi Fujisawa
- Department of Chemistry, University of Tsukuba, Tsukuba 305-8571 Japan
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Abstract
The shortest known type 1 copper binding loop (that of amicyanin, Ami) has been introduced into three different cupredoxin beta-barrel scaffolds. All of the loop-contraction variants possess copper centers with authentic type 1 properties and are redox active. The Cu(II) and Co(II) sites experience only small structural alterations upon loop contraction with the largest changes in the azurin variant (AzAmi), which can be ascribed to the removal of a hydrogen bond to the coordinating thiolate sulfur of the Cys ligand. In all cases, loop contraction leads to an increase in the pK(a) of the His ligand found on the loop in the reduced proteins, and in the pseudoazurin (Paz) and plastocyanin (Pc) variants the values are almost identical to that of Ami ( approximately 6.7). Thus, in Paz, Pc, and Ami, the length of this loop tunes the pK(a) of the His ligand. In the AzAmi variant, the pK(a) is 5.5, which is considerably higher than the estimated value for Az (<2), and other controlling factors, along with loop length, are involved. The reduction potentials of the loop-contraction variants are all lower than those of the wild-type proteins by approximately 30-60 mV, and thus this property of a type 1 copper site is fine-tuned by the C-terminal loop. The electron self-exchange rate constant of Paz is significantly diminished by the introduction of a shorter loop. However, in PcAmi only a 2-fold decrease is observed and in AzAmi there is no effect, and thus in these two cupredoxins loop contraction does not significantly influence electron-transfer reactivity. Loop contraction provides an active site environment in all of the cupredoxins which is preferable for Cu(II), whereas previous loop elongation experiments always favored the cuprous site. Thus, the ligand-containing loop plays an important role in tuning the entatic nature of a type 1 copper center.
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Affiliation(s)
- Sachiko Yanagisawa
- School of Natural Sciences, Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 7RU, UK
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27
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Bellú S, Hure E, Trapé M, Trossero C, Molina G, Drogo C, Williams PA, Atria AM, Muñoz Acevedo JC, Zacchino S, Sortino M, Campagnoli D, Rizzotto M. Synthesis, structure and antifungal properties of Co(II)–sulfathiazolate complexes. Polyhedron 2005. [DOI: 10.1016/j.poly.2004.12.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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28
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Matsunaga Y, Fujisawa K, Ibi N, Miyashita Y, Okamoto KI. Structural and Spectroscopic Characterization of First-Row Transition Metal(II) Substituted Blue Copper Model Complexes with Hydrotris(pyrazolyl)borate. Inorg Chem 2004; 44:325-35. [PMID: 15651879 DOI: 10.1021/ic049814x] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[CuL(SC(6)F(5))] (1) (L = hydrotris(3,5-diisopropyl-1-pyrazolyl)borate anion) has been reported as a good model for blue copper proteins [Kitajima, N.; Fujisawa, K.; Tanaka, M.; Moro-oka, Y. J. Am. Chem. Soc. 1992, 114, 9232-9233]. To obtain more structural and spectroscopic insight, the first-row transition metal(II) substituted complexes of Cu(II) (1) to Mn(II) (2), Fe(II) (3), Co(II) (4), Ni(II) (5), and Zn(II) (6) were synthesized and their crystal structures were determined. These model complexes have a distorted tetrahedral geometry arising from the tripodal ligand L. The d value, which is defined by the distance from the N(2)S basal plane to the metal(II) ion, and the bond angles such as N-M-N and S-M-N are good indicators of these structural distortions. The obtained complexes were characterized by UV-vis absorption, EPR, NMR, far-IR, and FT-Raman spectroscopies and electrochemical and magnetic properties. In UV-vis absorption spectra, the sulfur-to-metal(II) CT bands and the d-d transition bands are observed for 1 and 3-5. For 1, the strong sulfur to Cu(II) CT band at 663 nm, which is one of the unique properties of blue copper proteins, is observed. The CT energies of the Fe(II) (3), Co(II) (4), and Ni(II) (5) complexes are shifted to higher energy (308 and 355 nm for 3, 311 and 340 nm for 4, 357 and 434 nm for 5) and are almost the same as the corresponding Co(II)- and Ni(II)-substituted blue copper proteins. In the far-IR spectra, three far-IR absorption bands for 2-6 at ca. 400, ca. 350, and ca. 310 cm(-1) are also observed similar to those for 1. Other properties are consistent with their distorted tetrahedral geometries.
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Affiliation(s)
- Yuki Matsunaga
- Department of Chemistry, University of Tsukuba, Tsukuba 305-8571, Japan
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29
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Ralle M, Berry SM, Nilges MJ, Gieselman MD, van der Donk WA, Lu Y, Blackburn NJ. The Selenocysteine-Substituted Blue Copper Center: Spectroscopic Investigations of Cys112SeCys Pseudomonas aeruginosa Azurin. J Am Chem Soc 2004; 126:7244-56. [PMID: 15186162 DOI: 10.1021/ja031821h] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Azurin is a small electron-transfer protein belonging to the cupredoxin family. The Cu atom is located within a trigonal plane coordinated by two histidines (His46 and His117) and a cysteine (Cys112) with two more distant ligands (Gly45 and Met121) providing axial interactions. A Cys112SeCys derivative has been prepared by expressed protein ligation, and detailed UV/vis, EPR and EXAFS studies at the Cu and Se K-edges have been carried out. Marked changes are observed between the EPR parameters of the Cys112SeCys and WT azurin derivatives, which include a 2-fold increase in A(||), a decrease in g-values, and a large increase in rhombicity of the g-tensor. The Cu-Se and Se-Cu bond lengths obtained from analysis of the Cu and Se K-EXAFS of the oxidized protein were found to be 2.30 and 2.31 A, respectively, 0.14 A longer than the Cu-S distance of the WT protein. Unexpectedly, the Cu-Se bond lengths were found to undergo only minor changes during reduction, suggesting a very similar structure in both redox states and extending the "rack" hypothesis to the Se-substituted protein.
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Affiliation(s)
- Martina Ralle
- Department of Environmental & Biomolecular Systems, OGI School of Science & Engineering, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon 97006, USA
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30
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Funk T, Kennepohl P, Di Bilio AJ, Wehbi WA, Young AT, Friedrich S, Arenholz E, Gray HB, Cramer SP. X-ray Magnetic Circular Dichroism of Pseudomonas aeruginosa Nickel(II) Azurin. J Am Chem Soc 2004; 126:5859-66. [PMID: 15125678 DOI: 10.1021/ja036218d] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We show that X-ray magnetic circular dichroism (XMCD) can be employed to probe the oxidation states and other electronic structural features of nickel active sites in proteins. As a calibration standard, we have measured XMCD and X-ray absorption (XAS) spectra for the nickel(II) derivative of Pseudomonas aeruginosa azurin (NiAz). Our analysis of these spectra confirms that the electronic ground state of NiAz is high-spin (S = 1); we also find that the L(3)-centroid energy is 853.1(1) eV, the branching ratio is 0.722(4), and the magnetic moment is 1.9(4) mu(B). Density functional theory (DFT) calculations on model NiAz structures establish that orbitals 3d(x2-y2) and 3d(z2) are the two valence holes in the high-spin Ni(II) ground state, and in accord with the experimentally determined orbital magnetic moment, the DFT results also demonstrate that both holes are highly delocalized, with 3d(x2-y2) having much greater ligand character.
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Affiliation(s)
- Tobias Funk
- Physical Biosciences, LBNL, Cyclotron Road 1, Berkeley, California 94720, USA.
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31
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Dennison C, Sato K. Paramagnetic1H NMR Spectrum of the Cobalt(II) Derivative of Spinach Plastocyanin. Inorg Chem 2004; 43:1502-10. [PMID: 14966988 DOI: 10.1021/ic034861v] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The native type 1 copper ion of spinach plastocyanin has been substituted with Co(II). The UV/vis spectrum of this derivative is similar to those for other Co(II)-substituted cupredoxins. The paramagnetic 1H NMR spectrum of Co(II) plastocyanin has been completely assigned. A number of similar studies on Co(II) cupredoxins have been published, but this is the first such analysis of a substituted plastocyanin that possesses the archetypal type 1 active site. A truly representative comparison of the available paramagnetic 1H NMR data for Co(II) cupredoxins is now possible. We demonstrate in this work that there is very little difference in the metal-ligand contacts between the Co(II) derivatives of cupredoxins possessing a type 1 axial site (plastocyanin) and those having perturbed (rhombic) spectroscopic features.
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Affiliation(s)
- Christopher Dennison
- School of Natural Sciences, Bedson Building, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK.
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32
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Rizzi AC, Brondino CD, Calvo R, Baggio R, Garland MT, Rapp RE. Structure and magnetic properties of layered high-spin Co(II)(l-threonine)2(H2O)2. Inorg Chem 2003; 42:4409-16. [PMID: 12844314 DOI: 10.1021/ic026111b] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the structure and the magnetic properties of a cobalt(II) compound with the amino acid l-threonine, Co(C(4)H(8)NO(3))(2)(H(2)O)(2). It crystallizes in the orthorhombic chiral space group C222(1), with a = 5.843(5) A, b = 10.120(10) A, c = 22.36(3) A, and Z = 4. The Co(II) ion is in a deformed octahedral environment on a 2-fold symmetry axis parallel to the crystallographic axis b. It is bonded to two threonine molecules in a bidentate fashion, via one oxygen from the carboxylate end and the alpha-amino nitrogen. A water molecule occupies the third independent site. The Co(II) ions are arranged in layers with intralayer and interlayer distances of 5.84 and 11.18 A, respectively. Magnetic measurements data reflect the molecular character of a compound with weak exchange interactions. EPR measurements in polycrystalline and single-crystal samples indicate a distorted axial symmetry around the Co(II) ion, as expected from the structural results. Eigenvalues and eigenvectors of the g tensor are determined. The measured principal g values (5.81, 4.56, and 2.23) reflect a high-spin Co(II) ion, as suggested by the type of ligands and the molecular symmetry. From the incomplete collapse of the hyperfine structure we estimate 0.25 < |J| < 1.2 cm(-1) between neighboring Co(II) ions within a layer, transmitted through H-bonds. A higher limit |J'| < 0.07 cm(-1) is estimated for the exchange interactions between Co(II) ions in neighboring layers. From a global fit of a spin Hamiltonian with spin (3)/(2) to magnetization and EPR data we obtain a zero field splitting delta approximately 231 cm(-1) between the two lowest doublet states. The results are discussed in terms of the molecular and electronic structure of the compound.
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Affiliation(s)
- Alberto C Rizzi
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral, Güemes 3450, 3000 Santa Fe, Argentina
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33
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Dennison C, Sato K. Paramagnetic 1H NMR spectrum of nickel(II) pseudoazurin: investigation of the active site structure and the acid and alkaline transitions. Inorg Chem 2002; 41:6662-72. [PMID: 12470061 DOI: 10.1021/ic020303p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The paramagnetic (1)H NMR spectrum of Ni(II) pseudoazurin [(PA)Ni(II)] possesses a number of resonances exhibiting sizable Fermi-contact shifts. These have been assigned to protons associated with the four ligating amino acids, His40, Cys78, His81, and Met86. The shifts experienced by the C(gamma)H protons of the axial Met86 ligand are unprecedented compared to other Ni(II)- and Co(II)-substituted cupredoxins (the C(gamma)(1)H signal is found at 432.5 ppm at 25 degrees C). The large shift of protons of the axial Met86 ligand highlights a strong Ni(II)-S(Met) interaction in (PA)Ni(II). The paramagnetic (1)H NMR spectrum of (PA)Ni(II) is altered by decreasing and increasing the pH value from 8.0. At acidic pH a number of the hyperfine-shifted resonances undergo limited changes in their chemical shift values. This effect is assigned to the surface His6 residue whose protonation results in a structural modification of the active site. Increasing the pH value from 8.0 has a more significant effect on the paramagnetic (1)H NMR spectrum of (PA)Ni(II), and the alkaline transition can now be assigned to two surface lysine residues close to the active site of the protein. The effect of altering pH on the (1)H NMR spectrum of Ni(II) pseudoazurin is smaller than that previously observed in the Cu(II) protein indicating more limited structural rearrangements at the non-native metal site.
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34
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Kawatsu T, Kakitani T, Yamato T. Destructive Interference in the Electron Tunneling through Protein Media. J Phys Chem B 2002. [DOI: 10.1021/jp026035y] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Tsutomu Kawatsu
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Toshiaki Kakitani
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takahisa Yamato
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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35
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Kawatsu T, Kakitani T, Yamato T. On the Anomaly of the Tunneling Matrix Element in Long-Range Electron Transfer. J Phys Chem B 2002. [DOI: 10.1021/jp013975u] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tsutomu Kawatsu
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Toshiaki Kakitani
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takahisa Yamato
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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36
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Kawatsu T, Kakitani T, Yamato T. Worm Model for Electron Tunneling in Proteins: Consolidation of the Pathway Model and the Dutton Plot. J Phys Chem B 2001. [DOI: 10.1021/jp003918l] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Tsutomu Kawatsu
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Toshiaki Kakitani
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Takahisa Yamato
- Department of Physics, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
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37
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38
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Bonander N, Leckner J, Guo H, Karlsson BG, Sjölin L. Crystal structure of the disulfide bond-deficient azurin mutant C3A/C26A: how important is the S-S bond for folding and stability? EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:4511-9. [PMID: 10880975 DOI: 10.1046/j.1432-1033.2000.01501.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Azurin has a beta-barrel fold comprising eight beta-strands and one alpha helix. A disulfide bond between residues 3 and 26 connects the N-termini of beta strands beta1 and beta3. Three mutant proteins lacking the disulfide bond were constructed, C3A/C26A, C3A/C26I and a putative salt bridge (SB) in the C3A/S25R/C26A/K27R mutant. All three mutants exhibit spectroscopic properties similar to the wild-type protein. Furthermore, the crystal structure of the C3A/C26A mutant was determined at 2.0 A resolution and, in comparison to the wild-type protein, the only differences are found in the immediate proximity of the mutation. The mutants lose the 628 nm charge-transfer band at a temperature 10-22 degrees C lower than the wild-type protein. The folding of the zinc loaded C3A/C26A mutant was studied by guanidine hydrochloride (GdnHCl) induced denaturation monitored both by fluorescence and CD spectroscopy. The midpoint in the folding equilibrium, at 1.3 M GdnHCl, was observed using both CD and fluorescence spectroscopy. The free energy of folding determined from CD is -24.9 kJ.mol-1, a destabilization of approximately 20 kJ.mol-1 compared to the wild-type Zn2+-protein carrying an intact disulfide bond, indicating that the disulfide bond is important for giving azurin its stable structure. The C3A/C26I mutant is more stable and the SB mutant is less stable than C3A/C26A, both in terms of folding energy and thermal denaturation. The folding intermediate of the wild-type Zn2+-azurin is not observed for the disulfide-deficient C3A/C26A mutant. The rate of unfolding for the C3A/C26A mutant is similar to that of the wild-type protein, suggesting that the site of the mutation is not involved in an early unfolding reaction.
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Affiliation(s)
- N Bonander
- Department of Biochemistry and Biophysics, Lundberg Institute, Göteborg University and Chalmers University of Technology, Sweden
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39
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Kawatsu T, Kakitani T, Yamato T. A novel method for determining the electron tunneling pathway in protein. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(00)00039-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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40
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De Kerpel JOA, Pierloot K, Ryde U. Geometric and Electronic Structure of Co(II)-Substituted Azurin. J Phys Chem B 1999. [DOI: 10.1021/jp991359g] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jan O. A. De Kerpel
- Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Heverlee-Leuven, Belgium
| | - Kristine Pierloot
- Department of Chemistry, University of Leuven, Celestijnenlaan 200F, B-3001 Heverlee-Leuven, Belgium
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, S-221 00 Lund, Sweden
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41
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Abstract
1H NMR data applied to the paramagnetic cobalt(II) derivative of azurin from Pseudomonas aeruginosa have made it possible to show that the metal ion is bound to the protein in the unfolded state. The relaxation data as well as the low magnetic anisotropy of the metal ion indicate that the cobalt ion is tetrahedral in the unfolded form. The cobalt ligands have been identified as the residues Gly45, His46, Cys112 and His117. Met121 is not coordinated in the unfolded state. In this state, the metal ion is not constrained to adopt a bipyramidal geometry, as imposed by the protein when it is folded. This is clear confirmation of the rack-induced bonding mechanism previously proposed for the metal ion in azurin.
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Affiliation(s)
- C Romero
- Departamento de Química Inorgánica, Universitat de Valencia, Burjassot, Spain
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42
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Hellinga HW. Construction of a Blue Copper Analogue through Iterative Rational Protein Design Cycles Demonstrates Principles of Molecular Recognition in Metal Center Formation. J Am Chem Soc 1998. [DOI: 10.1021/ja980054x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Homme W. Hellinga
- Contribution from the Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710
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43
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Suzuki S, Deligeer, Yamaguchi K, Kataoka K, Shidara S, Iwasaki H, Sakurai T. Spectroscopic distinction between two Co(II) ions substituted for types 1 and 2 Cu in nitrite reductase. Inorganica Chim Acta 1998. [DOI: 10.1016/s0020-1693(97)00070-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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