Evolutionary change of the heme c electronic structure: ferricytochrome c-551 from Pseudomonas aeruginosa and horse heart ferricytochrome c. |
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Authors: | R M Keller K Wüthrich |
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Affiliation: | Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule, CH-8093 Zürich, Switzerland |
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Abstract: | Individual assignments of the 1H n.m.r. lines of heme c in reduced and oxidized cytochrome c-551 from were obtained by nuclear Overhauser enhancement and saturation transfer experiments. Comparison with the corresponding data on horse heart cytochrome c showed that the locations of high spin density on the heme c periphery as well as the in-plane principal axes x and y of the electronic g-tensor are rotated by approximately 90° in ferricytochrome c-551 relative to horse ferricytochrome c. High spin density in ferricytochrome c-551 is thus localized on the pyrrole ring III. While this pyrrole ring is well shielded in the interior of mammalian-type cytochromes c, it is more easily accessible in cytochrome c-551. It is suggested that this evolutionary change of the heme c electronic structure would be compatible with the hypothesis that the electron transfer in both species is via solvent exposed peripheral ring carbon atoms. |
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