Relationship between redox function and protein stability of cytochromes c

Electrochemical, 1H NMR, and optical studies on mesophile Pseudomonas aeruginosa cytochrome c551, its single (F34Y) and quintuple (F7A/V13M/F34Y/E43Y/V78I) mutants, and thermophile Hydrogenobacter thermophilus cytochrome c552 at wide temperature range demonstrated that the stable protein exhibits the low redox potential predominantly due to the enthalpic contribution to the redox reaction. The overall stability of the oxidized form was shown to determine the stability of the Fe-methionine coordination bond, which then directly regulates the redox function.