Takeda Taku, Sonoyama Takafumi, Takayama Shin-ichi J, Mita Hajime, Yamamoto Yasuhiko, Sambongi Yoshihiro
Graduate School of Biosphere Science, Hiroshima University, CREST of Japan Science and Technology Corporation, Higashi-Hiroshima, Japan.
Biosci Biotechnol Biochem. 2009 Feb;73(2):366-71. doi: 10.1271/bbb.80607. Epub 2009 Feb 7.
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.
在25℃、pH 7.0条件下，通过在不同浓度变性剂硫氰酸胍存在下的索雷特吸收测量，系统监测了来自两种嗜热菌和一种嗜温菌的三种同源细胞色素c氧化态和还原态的稳定性。嗜热嗜热栖热菌细胞色素c(552)在两种氧化还原状态下最稳定，其次是中度嗜热嗜热栖热放线菌细胞色素c(552)，然后是嗜温铜绿假单胞菌细胞色素c(551)。对这三种蛋白质及其相互变体进行的进一步稳定性和电化学分析表明，与血红素具有不同疏水相互作用的变体中，在两种氧化还原状态下稳定性较高的变体具有较低的氧化还原电位。因此，这些细胞色素c可能通过相关的稳定性和氧化还原电位限制适应了原始细菌的细胞环境，这些限制部分受血红素周围疏水性的调节。
