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Article Dans Une Revue Biochimica biophysica acta (BBA) - Bioenergetics Année : 2023

Individual heme a and heme a3 contributions to the Soret absorption spectrum of the reduced bovine cytochrome c oxidase

Résumé

Bovine cytochrome c oxidase (CcO) contains two hemes, a and a3, chemically identical but differing in coordination and spin state. The Soret absorption band of reduced aa3-type cytochrome c oxidase consists of overlapping bands of the hemes a2+ and a32+. It shows a peak at ∼444 nm and a distinct shoulder at ∼425 nm. However, attribution of individual spectral lineshapes to hemes a2+ and a32+ in the Soret is controversial. In the present work, we characterized spectral contributions of hemes a2+ and a32+ using two approaches. First, we reconstructed bovine CcO heme a2+ spectrum using a selective Ca2+-induced spectral shift of the heme a2+. Second, we investigated photobleaching of the reduced Thermus thermophilus ba3- and bovine aa3-oxidases in the Soret induced by femtosecond laser pulses in the Q-band. The resolved spectra show splitting of the electronic B0x-, B0y-transitions of both reduced hemes. The heme a2+ spectrum is shifted to the red relative to heme a32+ spectrum. The ∼425 nm shoulder is mostly attributed to heme a32+.
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hal-03862370 , version 1 (02-11-2023)

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Artem Diuba, Tatiana Vygodina, Natalia Azarkina, Alexander Arutyunyan, Tewfik Soulimane, et al.. Individual heme a and heme a3 contributions to the Soret absorption spectrum of the reduced bovine cytochrome c oxidase. Biochimica biophysica acta (BBA) - Bioenergetics, 2023, 1864, pp.148937. ⟨10.1016/j.bbabio.2022.148937⟩. ⟨hal-03862370⟩
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