New insight into the mechanism of mitochondrial cytochrome c function

Abstract

We investigate functional role of the P76GTKMIFA83 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 P76GTKMIFA83 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 c oxidoreductase (complex III) and cytochrome c oxidase (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 P76GTKMIFA83 sequence that reduce its ability to undergo conformational rearrangements. With this, we study the succinate–cytochrome c reductase and cytochrome c oxidase 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 P76GTKMIFA83 fragment in the electron transport function of cytochrome c.

Redox state changes of mitochondrial cytochromes in brain and breast cancers by Raman spectroscopy and imaging

“…The band at 1584 cm -1 represents the reduced form of cytochrome and it is not observed in the oxidized form. Some of the peaks of the oxidized form of Cyt c (around 750, 1130, 1172, 1314, 1374, 1570-1573 and 1639 cm -1 ) have the same positions as the reduced form 19 , but their intensities are significantly lower. 11,[19][20][21] In the view of the results for animal brain it would be extremely valuable to control cytochrome activity in humans.…”

“…Some of the peaks of the oxidized form of Cyt c (around 750, 1130, 1172, 1314, 1374, 1570-1573 and 1639 cm -1 ) have the same positions as the reduced form 19 , but their intensities are significantly lower. 11,[19][20][21] In the view of the results for animal brain it would be extremely valuable to control cytochrome activity in humans. To help address these challenges Fig.2A shows Raman enhancement of cytochromes for ex vivo human brain tissue of highly aggressive medulloblastoma, where the blue arrows shows the Raman peaks of Cyt c (reduced form).…”

Redox Imbalance and Biochemical Changes in Cancer by probing redox-sensitive mitochondrial cytochromes in label-free visible resonance Raman imaging

“…The band at 1584 cm -1 represents the reduced form of cytochrome c and it is not observed in the oxidized form. Some of the peaks of the oxidized form of cytochrome c (around 750, 1130, 1172, 1314, 1374, 1570-1573 and 1634 cm -1 ) have the same positions as the reduced form 43 , but their intensities are significantly lower except the band 1634 cm -1 corresponding to the ferric cytochrome c as presented in Fig. 4.…”

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

“…Its main function is its participation in the electron transport chain of the inner mitochondrial membrane (IMM). Cyt c is reversibly reduced and oxidized as an electron is transferred from ubiquinol-cytochrome c reductase (complex III) to cyt c oxidase (complex IV) in the mitochondrial respiratory chain [221]. Premature death of retinal cells occurs prior to the development of other lesions characteristic of retinopathy, suggesting that it may play a critical role in the development of DR [222].…”