Stabilization Mechanism of Cytochrome c_<552> from a Moderately Thermophilic Bacterium, Hydrogenophilus thermoluteolus

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Cytochrome c552 (PH c552) from moderately thermophilic Hydrogenophilus thermoluteolus exhibits stability intermediate between those of cytochrome c552 (HT c552) from thermophilic Hydrogenobacter thermophilus and cytochrome c551 (PA c551) from mesophilic Pseudomonas aeruginosa. To understand the mechanism of stabilization of PH c552, we introduced mutations into PH c552 at five sites, which, in HT c552, are occupied by the amino acids responsible for stability higher than the less stable PA c551. When PH c552 Val-78 was mutated to Ile, as found in HT c552, the resulting variant showed increased stability. Mutation of Ala-7, Met-13, and Tyr-34 to the corresponding residues in PA c551 (Phe, Val, and Phe, respectively) resulted in destabilization. We also found that PH c552 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 c552 is due to the amino acids at these five sites.
社団法人日本農芸化学会の論文
2008-08-23