Electrochemistry of the CuA domain of Thermus thermophilus cytochrome ba
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| Authors: | C Immoos Michael G Hill Donita Sanders James A Fee Claire E Slutter John H Richards Harry B Gray |
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| Institution: | (1) Department of Chemistry, Occidental College, Los Angeles, CA 90041, USA, US;(2) Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA, US;(3) Department of Biology, University of California at San Diego, La Jolla, CA 92093, USA, US |
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| Abstract: | The electrochemistry of a water-soluble fragment from the CuA domain of Thermus thermophilus cytochrome ba
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has been investigated. At 25 °C, CuA exhibits a reversible reduction at a pyridine-4-aldehydesemicarbazone-modified gold electrode (0.1 M Tris, pH 8) with E° = 0.24 V vs NHE. Thermodynamic parameters for the Cu(Cys)2Cu]+/0 electrode reaction were determined by variable-temperature electrochemistry (ΔS°rc = –5.4(12) eu, ΔS° = –21.0(12) eu, ΔH° = –11.9(4) kcal/mol;ΔG° = –5.6 (11) kcal/mol). The relatively small reaction entropy is consistent with a low reorganization energy for Cu(Cys)2Cu]+/0 electron transfer. An irreversible oxidation of Cu(Cys)2Cu]+ at 1 V vs NHE confirms that the CuII:CuII state of CuA is significantly destabilized relative to the CuII state of analogous blue-copper proteins.
Received: 3 June 1996 / Accepted: 26 August 1996 |
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| Keywords: | CuA domain Thermus thermophilus Cytochrome ba3 Electrochemistry |
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