Amino Acid Substitutions in the Non-Ordered Ω-Loop 70–85 Affect Electron Transfer Function and Secondary Structure of Mitochondrial Cytochrome cстатья
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Дата последнего поиска статьи во внешних источниках: 6 октября 2021 г.
Аннотация:Abstract: The secondary structure of horse cytochrome c with mutations in the P76GTKMIFA83 site of the Ω-loop, exhibiting reduced efficiency of electron transfer, were studied. CD spectroscopy studies showed that the ordering of mutant structure increases by 3–6% compared to that of the WT moleculesduetothehighercontentof β-structuralelements. TheIRspectroscopydataareconsistent with the CD results and demonstrate that some α-helical elements change into β-structures, and the amount of the non-structured elements is decreased. The analysis of the 1H-NMR spectra demonstrated that cytochrome c mutants have a well-determined secondary structure with some specific features related to changes in the heme microenvironment. The observed changes in the structure of cytochrome c mutants are likely to be responsible for the decrease in the conformational mobility of the P76GTKMIFA83 sequence carrying mutations and for the decline in succinate:cytochrome c-reductase and cytochrome c-oxidase activities in the mitoplast system in the presence of these cytochromes c. We suggest that the decreased efficiency of the electron transfer of the studied cytochromes c may arise due to: (1) the change in the protein conformation in sites responsible for the interaction of cytochrome c with complexes III and IV and (2) the change in the heme conformation thatdeterioratesitsoptimalorientationtowardsdonorandacceptorincomplexesIIIandIVtherefore slowsdownelectrontransfer. Theresultsobtainedareconsistentwiththepreviouslyproposedmodel of mitochondrial cytochrome c functioning associated with the deterministic mobility of protein globule parts.