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. 1986 Jun;83(11):3693–3697. doi: 10.1073/pnas.83.11.3693

Redox pathways in electron-transfer proteins: correlations between reactivities, solvent exposure, and unpaired-spin-density distributions.

G Tollin, L K Hanson, M Caffrey, T E Meyer, M A Cusanovich
PMCID: PMC323589  PMID: 3012528

Abstract

The relative reactivities toward reduction by free flavin semiquinones of cytochromes (c-type cytochromes, cytochrome b5, c'-type cytochromes) iron-sulfur proteins (high-redox-potential ferredoxins, rubredoxins, low-redox-potential ferredoxins), and blue copper proteins (plastocyanin, azurins) are shown to correlate with calculations of the solvent exposure of the various prosthetic groups. In the case of the c-type cytochromes, one of the major centers of exposure is the sulfur atom of the thioether bridge that covalently links heme ring C to the protein. Charge-iterative extended Hückel calculations on a heme c model indicate that both porphyrin pi and Fe(III)d pi orbitals can delocalize onto the bridging sulfur atom. Unpaired spin densities are comparable to those obtained for individual aromatic porphyrin ring carbon atoms. Thus, the exposed sulfur of ring C may act to facilitate electron transfer.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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