title: Stabilization mechanism of cytochrome c552 from a moderately thermophilic bacterium, Hydrogenophilus thermoluteolus.
abstract: Cytochrome c(552) (PH c(552)) from moderately thermophilic Hydrogenophilus thermoluteolus exhibits stability intermediate between those of cytochrome c(552) (HT c(552)) from thermophilic Hydrogenobacter thermophilus and cytochrome c(551) (PA c(551)) from mesophilic Pseudomonas aeruginosa. To understand the mechanism of stabilization of PH c(552), we introduced mutations into PH c(552) at five sites, which, in HT c(552), are occupied by the amino acids responsible for stability higher than the less stable PA c(551). When PH c(552) Val-78 was mutated to Ile, as found in HT c(552), the resulting variant showed increased stability. Mutation of Ala-7, Met-13, and Tyr-34 to the corresponding residues in PA c(551) (Phe, Val, and Phe, respectively) resulted in destabilization. We also found that PH c(552) Lys-43 contributed to stability through the formation of an attractive electrostatic interaction with Asp-39. These results suggest that the intermediate stability of PH c(552) is due to the amino acids at these five sites.
authors.affiliation: Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, Higashi-Hiroshima, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Hakamada
authors.forename: Takafumi
authors.initials: T
authors.lastname: Sonoyama
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Ichiki
authors.forename: Shota
authors.initials: S
authors.lastname: Nakamura
authors.forename: Susumu
authors.initials: S
authors.lastname: Uchiyama
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sambongi
mesh_terms: D000595:Amino Acid Sequence; D017124:Conserved Sequence; D003574:Cytochrome c Group / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D043363:Hydrogenophilaceae / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D055672:Static Electricity; D013696:Temperature; D013816:Thermodynamics
chemical_list: D003574:Cytochrome c Group; C022302:cytochrome C-552