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Electron transfer among the Cu A ‐, heme b ‐ and a 3 ‐centers of Thermus thermophilus cytochrome ba 3
Author(s) -
Farver Ole,
Chen Ying,
Fee James A.,
Pecht Israel
Publication year - 2006
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2006.05.013
Subject(s) - thermus thermophilus , chemistry , heme , paracoccus denitrificans , cytochrome , cytochrome c peroxidase , heme a , electron transfer , cytochrome c , cytochrome c oxidase , stereochemistry , intramolecular force , radiolysis , hemeprotein , photochemistry , crystallography , biochemistry , radical , enzyme , mitochondrion , escherichia coli , gene
The 1‐methyl‐nicotinamide radical (MNA ∗ ), produced by pulse radiolysis has previously been shown to reduce the Cu A ‐site of cytochromes aa 3 , a process followed by intramolecular electron transfer (ET) to the heme a but not to the heme a 3 [Farver, O., Grell, E., Ludwig, B., Michel, H. and Pecht, I. (2006) Rates and equilibrium of CuA to heme a electron transfer in Paracoccus denitrificans cytochrome c oxidase. Biophys. J. 90, 2131–2137]. Investigating this process in the cytochrome ba 3 of Thermus thermophilus ( Tt ), we now show that MNA ∗ also reduces Cu A with a subsequent ET to the heme b and then to heme a 3 , with first‐order rate constants 11 200 s −1 , and 770 s −1 , respectively. The results provide clear evidence for ET among the three spectroscopically distinguishable centers and indicate that the binuclear a 3 ‐Cu B center can be reduced in molecules containing a single reduction equivalent.