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Laia CAT, Costa SMB. Interaction of Zinc Tetrasulfonated Phthalocyanine with Cytochromecin Water and Triton-X 100 Micelles. J Phys Chem B 2008; 112:4276-82. [DOI: 10.1021/jp076100+] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Laia CAT, Costa SMB, Vieira Ferreira LF. Electron-transfer mechanism of the triplet state quenching of aluminium tetrasulfonated phthalocyanine by cytochrome c. Biophys Chem 2006; 122:143-55. [PMID: 16624476 DOI: 10.1016/j.bpc.2006.03.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2005] [Revised: 03/09/2006] [Accepted: 03/09/2006] [Indexed: 11/19/2022]
Abstract
The mechanism of electron-transfer from aluminium tetrasulfonated phthalocyanine triplet state to cytochrome c was investigated in this work. This reaction successfully quenches the dye triplet state due to the formation of complexes between the solute and the protein at the active site. The electron-transfer rate constant is around 3x10(7) s(-1), and is in accordance with previous results for the singlet excited state quenching [C.A.T. Laia, S.M.B. Costa, D. Phillips, A. Beeby. Electron-transfer kinetics in sulfonated aluminum phthalocyanines/cytochrome c complexes, J. Phys. Chem. B 108 (2004) 7506-7514.] in the framework of the Marcus theory, with a reorganization energy equal to 0.94 eV. The complex formation is diffusion controlled, but heterogeneities of the protein surface charge distribution lead to quenching rate constants smaller than predicted on a hard-spheres model with electrostatic interactions. Also the binding equilibrium constant is strongly affected by this phenomenon. Ionic strength plays an important role on the complex formation, but its effect on the unimolecular electron-transfer rate constant is negligible within experimental error.
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Affiliation(s)
- César A T Laia
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 Lisboa, Portugal.
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Baddam S, Bowler BE. Tuning the Rate and pH Accessibility of a Conformational Electron Transfer Gate. Inorg Chem 2006; 45:6338-46. [PMID: 16878944 DOI: 10.1021/ic0603712] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methods to fine-tune the rate of a fast conformational electron transfer (ET) gate involving a His-heme alkaline conformer of iso-1-cytochrome c (iso-1-Cytc) and to adjust the pH accessibility of a slow ET gate involving a Lys-heme alkaline conformer are described. Fine-tuning the fast ET gate employs a strategy of making surface mutations in a substructure unfolded in the alkaline conformer. To make the slow ET gate accessible at neutral pH, the strategy involves mutations at buried sequence positions which are expected to more strongly perturb the stability of native versus alkaline iso-1-Cytc. To fine-tune the rate of the fast His 73-heme ET gate, we mutate the surface-exposed Lys 79 to Ala (A79H73 variant). This mutation also simplifies ET gating by removing Lys 79, which can serve as a ligand in the alkaline conformer of iso-1-Cytc. To adjust the pH accessibility of the slow Lys 73-heme ET gate, we convert the buried side chain Asn 52 to Gly and also mutate Lys 79 to Ala to simplify ET gating (A79G52 variant). ET kinetics is studied as a function of pH using hexaammineruthenium(II) chloride (a6Ru2+) to reduce the variants. Both variants show fast direct ET reactions dependent on [a6Ru2+] and slower gated ET reactions that are independent of [a6Ru2+]. The observed gated ET rates correlate well with rates for the alkaline-to-native state conformational change measured independently. Together with the previously reported H73 variant (Baddam, S.; Bowler, B. E. J. Am. Chem. Soc. 2005, 127, 9702-9703), the A79H73 variant allows His 73-heme-mediated ET gating to be fine-tuned from 75 to 200 ms. The slower Lys 73-heme (15-20 s time scale) ET gate for the A79G52 variant is now accessible over the pH range 6-8.
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Affiliation(s)
- Saritha Baddam
- Department of Chemistry and Biochemistry, University of Denver, 2190 East Iliff Avenue, Denver, CO 80208-2436, USA
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Laia CAT, Costa SMB. Interactions of a Sulfonated Aluminum Phthalocyanine and Cytochrome c in Micellar Systems: Binding and Electron-Transfer Kinetics. J Phys Chem B 2004. [DOI: 10.1021/jp047616l] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- César A. T. Laia
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 Lisboa, Portugal
| | - Sílvia M. B. Costa
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 Lisboa, Portugal
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Laia CAT, Costa SMB, Phillips D, Beeby A. Electron-Transfer Kinetics in Sulfonated Aluminum Phthalocyanines/Cytochrome c Complexes. J Phys Chem B 2004. [DOI: 10.1021/jp036675g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- César A. T. Laia
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 LISBOA, Portugal, Department of Chemistry, Imperial College, Exhibition Road, London SW7 2AY, U.K., and Chemistry Department, University of Durham, South Road, Durham DH1 3LE, U.K
| | - Sílvia M. B. Costa
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 LISBOA, Portugal, Department of Chemistry, Imperial College, Exhibition Road, London SW7 2AY, U.K., and Chemistry Department, University of Durham, South Road, Durham DH1 3LE, U.K
| | - David Phillips
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 LISBOA, Portugal, Department of Chemistry, Imperial College, Exhibition Road, London SW7 2AY, U.K., and Chemistry Department, University of Durham, South Road, Durham DH1 3LE, U.K
| | - Andrew Beeby
- Centro de Química-Estrutural, Complexo 1, Instituto Superior Técnico, 1049-001 LISBOA, Portugal, Department of Chemistry, Imperial College, Exhibition Road, London SW7 2AY, U.K., and Chemistry Department, University of Durham, South Road, Durham DH1 3LE, U.K
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Kornilova AY, Wishart JF, Ogawa MY. Effect of surface charges on the rates of intermolecular electron-transfer between de novo designed metalloproteins. Biochemistry 2001; 40:12186-92. [PMID: 11580294 DOI: 10.1021/bi011156u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A de novo designed coiled-coil metalloprotein was prepared that uses electrostatic interactions to control both its conformational and bimolecular electron-transfer properties. The title protein exists as a coiled-coil heterodimer of the [Ru(trpy)(bpy)-KK(37-mer)] and [Ru(NH(3))(5)-EE(37-mer)] polypeptides which is formed by interhelix electrostatic attractions. Circular dichroism studies show that the electrostatic heterodimer has K(d) = 0.19 +/- 0.03 microM and is 96% helical at high concentrations. Intercomplex electron-transfer reactions were studied that involve the [Ru(NH(3))(5)-H21](2+) electron-donor and the [Ru(trpy)(bpy)-H21](3+) electron-acceptor belonging to different electrostatic dimers. An important feature of the designed metalloprotein is its two cationic redox centers embedded within protein surfaces having opposite charge. Thus, the Ru(II)(NH(3))(5)-H21 site was placed on the surface of one chain of the coiled-coil which was made to be positively charged, and the Ru(III)(trpy)(bpy)-H21 site was placed on the surface of the other chain which was negatively charged. The rates of intermolecular electron-transfer increased from (1.9 +/- 0.4) x 10(7) M(-1) s(-1) to (3.7 +/- 0.5) x 10(7) M(-1) s(-1) as the ionic strength was increased from 0.01 to 0.20 M. This indicates that the electrostatic repulsion between the ruthenium centers dominates the kinetics of these reactions. However, the presence of the oppositely charged protein surfaces in the coiled-coils creates an electrostatic recognition domain that substantially ameliorates the effects of this repulsion.
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Affiliation(s)
- A Y Kornilova
- Department of Chemistry and Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio 43403, USA
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