Redox pathways in electron-transfer proteins: correlations between reactivities, solvent exposure, and unpaired-spin-density distributions.
- 1 June 1986
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 83 (11), 3693-3697
- https://doi.org/10.1073/pnas.83.11.3693
Abstract
The relative reactivities toward reduction by free flavin semiquinones of cytochromes (c-type cytochromes, cytochromes 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 Huckel 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.This publication has 13 references indexed in Scilit:
- Kinetics of electron transfer between cytochromes c' and the semiquinones of free flavin and clostridial flavodoxinBiochemistry, 1986
- Kinetics of reduction of high redox potential ferredoxins by the semiquinones of Clostridium pasteurianum flavodoxin and exogenous flavin mononucleotide. Electrostatic and redox potential effectsBiochemistry, 1985
- Helix movements and the reconstruction of the haem pocket during the evolution of the cytochrome c familyJournal of Molecular Biology, 1985
- Electron-transfer reactions of photoreduced flavin analogs with c-type cytochromes: quantitation of steric and electrostatic factorsBiochemistry, 1984
- Dictionary of protein secondary structure: Pattern recognition of hydrogen‐bonded and geometrical featuresBiopolymers, 1983
- Correlation between rate constant for reduction and redox potential as a basis for systematic investigation of reaction mechanisms of electron transfer proteins.Proceedings of the National Academy of Sciences, 1983
- Individual 1H-NMR assignments for the heme groups and the axially bound amino acids and determination of the coordination geometry at the heme iron in a mixture of two isocytochromes c-551 from Rhodopseudomonas gelatinosaBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1983
- Determination of the coordination geometry at the heme iron in three cytochromes c from Saccharomyces cerevisiae and from Candida krusei based on individual 1H-NMR assignments for heme c and the axially coordinated amino acidsBiochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology, 1983
- Structure of cytochrome c551 from Pseudomonas aeruginosa refined at 1.6 Å resolution and comparison of the two redox formsJournal of Molecular Biology, 1982
- The interpretation of protein structures: Estimation of static accessibilityJournal of Molecular Biology, 1971