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Electron-transfer studies with the CuA domain of Thermus thermophilus cytochrome ba_3

Slutter, Claire E. and Langen, Ralf and Sanders, Donita and Lawrence, Stephen M. and Wittung, Pernilla and Di Bilio, Angel J. and Hill, Michael G. and Fee, James A. and Richards, John H. and Winkler, Jay R. and Malmström, Bo G. (1996) Electron-transfer studies with the CuA domain of Thermus thermophilus cytochrome ba_3. Inorganica Chimica Acta, 243 (1-2). pp. 141-145. ISSN 0020-1693. doi:10.1016/0020-1693(95)04901-0.

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Flash photolysis has been used to initiate electron transfer from excited tris(2,2′-bipyridyl)ruthenium(II) to the Cu_A site of a soluble domain from subunit II of Thermus thermophilus cytochrome ba_3. Luminescence quenching of the excited state of the ruthenium(II) complex was observed at low protein concentrations (20–200 μM Cu_A domain), with second-order rate constants of 2.9 × 10^9 and 1.3 × 10^9 M^(−1) s^(−1) at low and high ionic strength, respectively. Transient absorption measurements demonstrate that 10–20% of the quenching arises from electron transfer (ET). At high protein concentrations (>250 μM Cu_A) and low ionic strength (5 mM Tris, pH 8.1), the quenching rate saturates due to ground-state complex formation; a first-order rate constant of 1.5 × 10^5 s^(−1) was estimated for ET in the complex. Given the high driving forces involved (ΔG° = 1.1 eV), it is possible that these ET reactions occur in the inverted driving-force regime. Spectroscopic measurements indicate that the T. thermophilus Cu_A domain and horse heart cytochrome c form a complex at low ionic strength, with an apparent dissociation constant K_d ∼ 5 μM.

Item Type:Article
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URLURL TypeDescription
Wittung, Pernilla0000-0003-1058-1964
Winkler, Jay R.0000-0002-4453-9716
Additional Information:© 1996 Elsevier Science S.A. This investigation has been supported by the National Science Foundation, the National Institutes of Health (GM35342, JAF; GM16424, IBR), an NIH Predoctoral Training Grant (GM07616, CBS), the Arnold and Mabel Beckman Foundation, and the Swedish Natural Science Research Council.
Funding AgencyGrant Number
NIH Postdoctoral FelowshipGM07616
Arnold and Mabel Beckman FoundationUNSPECIFIED
Swedish Natural Science Research CouncilUNSPECIFIED
Subject Keywords:Cytochrome c; Cytochrome oxidase; Copper A; Binuclear copper; Electron transfer; Tris(2,2′-bipyridyl)ruthenium(II)
Issue or Number:1-2
Record Number:CaltechAUTHORS:20150428-074946222
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Official Citation:Claire E. Slutter, Ralf Langen, Donita Sanders, Stephen M. Lawrence, Pernilla Wittung, Angel J. Di Bilio, Michael G. Hill, James A. Fee, John H. Richards, Jay R. Winkler, Bo G. Malmström, Electron-transfer studies with the CuA domain of Thermus thermophilus cytochrome ba3, Inorganica Chimica Acta, Volume 243, Issues 1–2, 29 February 1996, Pages 141-145, ISSN 0020-1693, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57033
Deposited By: Ruth Sustaita
Deposited On:28 Apr 2015 16:06
Last Modified:10 Nov 2021 21:07

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