title: Correlation between the stability and redox potential of three homologous cytochromes c from two thermophiles and one mesophile.
abstract: The stability of the oxidized and reduced forms of three homologous cytochromes c from two thermophiles and one mesophile was systematically monitored by means of Soret absorption measurements in the presence of various concentrations of a denaturant, guanidine thiocyanate, at pH 7.0 at 25 degrees C. Thermophilic Hydrogenobacter thermophilus cytochrome c(552) was the most stable in both redox states, followed by moderately thermophilic Hydrogenophilus thermoluteolus cytochrome c(552), and then mesophilic Pseudomonas aeruginosa cytochrome c(551). Further stability and electrochemical analysis of the three proteins and the reciprocal variants, which exhibited a different hydrophobic interaction with the heme, showed that the one with the higher stability in both redox states had the lower redox potential. Consequently, these cytochromes c probably adapted to the cellular environments of the original bacteria with correlated stability and redox potential constraints, which are in part regulated by the hydrophobicity around the heme.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, Higashi-Hiroshima, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Takeda
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sonoyama
authors.forename: Shin-ichi J
authors.initials: SJ
authors.lastname: Takayama
authors.forename: Hajime
authors.initials: H
authors.lastname: Mita
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sambongi
mesh_terms: D000042:Absorption; D045304:Cytochromes c / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004563:Electrochemistry; D004795:Enzyme Stability; D006146:Guanidines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D043363:Hydrogenophilaceae / Q000201:enzymology*; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D011487:Protein Conformation; D011489:Protein Denaturation / Q000187:drug effects; D011549:Pseudomonas / Q000201:enzymology*; D017385:Sequence Homology; D013696:Temperature; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: D006146:Guanidines; D013861:Thiocyanates; C054436:guanidine thiocyanate; D045304:Cytochromes c