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Published December 1996 | public
Journal Article

Electrochemistry of the Cu_A domain of Thermus thermophilus cytochrome ba _3

Abstract

The electrochemistry of a water-soluble fragment from the Cu_A domain of Thermus thermophilus cytochrome ba _3 has been investigated. At 25  °C, Cu_A 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 Cu^(II):Cu^(II) state of Cu_A is significantly destabilized relative to the Cu^(II) state of analogous blue-copper proteins.

Additional Information

© 1996 SBIC. Received: 3 June 1996; Accepted: 26 August 1996. This work was supported by the NIH (DK19038 to H.B.G.; GM35342 to J.A.F.; GM16424 to J.H.R.; GM07616 to C.E.S.), the Research Corporation (M.G.H.), the Camille and Henry Dreyfus Foundation (Faculty Start-up Grant to M.G.H.), and the NSF (DUE-9551647).

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023