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Pseudomonas aeruginosa cytochrome c(sub 551) and a series of its mutants exhibiting various thermostabilities are studied by paramagnetic (super 1)H NMR and cyclic voltammetry to elucidate the molecular mechanics responsible for control of the redox potentials [E(super o')] of the proteins. The study revealed that the [E(super o')] value of the protein is regulated by two molecular mechanisms operating independently of each other.

A new pressure-proof cell compartment installed in a circular dichroic spectrometer is developed. The analysis for both redox states of the two proteins shows that the stability of oxidized cyt c influences its redox function more than the reduced form does.

Electrochemical measurements taken at 25 degree Celsius using temperature dependent cyclic voltammetry were utilized for studying the relationship between redox function and protein stability of cytochromes c. The findings suggest that the overall protein stability, Fe-S bond stability, and redox property of cytochrome c were mutually related.

The results of paramagnetic (Super1) H NMR and optical studies on a homologous cytochrome c(cyt c) series, which demonstrate that interactions among amino acid side chains in distal regions influence heme axial coordinations in cyt c is presented. The conclusion states that alteration in interaction among acid side chains in the protein interior influence the stability of Fe-methionine coordination at the heme active site, which in turn affects thermostability of the protein.