Electron transfer among the CuA-, heme b- and a3-centers of Thermus thermophilus cytochrome ba3 |
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Authors: | Farver Ole Chen Ying Fee James A Pecht Israel |
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Institution: | Institute of Analytical Chemistry, The Danish University of Pharmaceutical Sciences, Copenhagen, Denmark. |
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Abstract: | 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 11200 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. |
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Keywords: | Cytochrome ba3 Cytochrome c oxidases Electron transfer Pulse radiolysis Thermus thermophilus |
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