New insight into the mechanism of mitochondrial cytochrome c function

作者：Chertkova Rita V^*; Brazhe Nadezda A^*; Bryantseva Tatiana V; Nekrasov Alexey N; Dolgikh Dmitry A; Yusipovich Alexander I; Sosnovtseva Olga; Maksimov Georgy V; Rubin Andrei B; Kirpichnikov Mikhail P

来源：PLos One, 2017, 12(5): e0178280.

DOI：10.1371/journal.pone.0178280

We investigate functional role of the P(76)GTKMIFA(83) fragment of the primary structure of cytochrome c. Based on the data obtained by the analysis of informational structure (ANIS), we propose a model of functioning of cytochrome c. According to this model, conformational rearrangements of the P(78)GTKMIFA(83) loop fragment have a significant effect on conformational mobility of the heme. It is suggested that the conformational mobility of cytochrome c heme is responsible for its optimal orientation with respect to electron donor and acceptor within ubiquinol cytochrome coxidoreductase (complex III) and cytochrome coxidase (complex IV), respectively, thus, ensuring electron transfer from complex III to complex IV. To validate the model, we design several mutant variants of horse cytochrome c with multiple substitutions of amino acid residues in the P(78)GTKMIFA(83) sequence that reduce its ability to undergo conformational rearrangements. With this, we study the succinate cytochrome c reductase and cytochrome coxidase activities of rat liver mitoplasts in the presence of mutant variants of cytochrome c. The electron transport activity of the mutant variants decreases to different extent. Resonance Raman spectroscopy (RRS) and surface-enhanced Raman spectroscopy (SERS) data demonstrate, that all mutant cytochromes possess heme with the higher degree of ruffling deformation, than that of the wild type (WT) cytochrome c. The increase in the ruffled deformation of the heme of oxidized cytochromes correlated with the decrease in the electron transport rate of ubiquinol cytochrome c reductase (complex III). Besides, all mutant cytochromes have lower mobility of the pyrrol rings and methine bridges, than WT cytochrome c. We show that a decrease in electron transport activity in the mutant variants correlates with conformational changes and reduced mobility of heme porphyrin. This points to a significant role of the P(78)GTKMIFA(83) fragment in the electron transport function of cytochrome c.

• 出版日期2017-5-31