Structural-Functional Characterization of Cytochrome b in bc1 and b6 f Complexes along with Polymorphic Analysis
Structural-Functional Characterization of Cytochrome b in bc1 and b6 f Complexes along with Polymorphic Analysis
Mohsin Shad1, Muhammad Usman2 and Qurratulann Afza Gardner1*
ABSTRACT
Mitochondrial cytochrome b (cyt b) transfers the electrons in bc1 complex from ubiquinone to cytochrome c reductase in the mitochondrial respiratory chain, and similarly in b6f enzyme complex, from plastoquinol (QH2) to plastocyanin (Pc) within the thylakoid membrane. Mitochondrial cyt b in bc1 complexes contains eight transmembrane helices A to H; two of these, B and E along with two histidines, are cross-linked with two hemes located at the top and bottom of the membrane. The b6f complex contains four large subunits which include cytochrome f, b, Rieske iron-sulfur protein, and subunit IV. Electrons transferred through these complexes are responsible for the pumping of protons across the membrane to produce ATP through ATP synthase. The present review provides the structural comparison of mitochondrial cyt b in ten model organisms targeting archaea, prokaryotes, and eukaryotes, highlighting phylogenetic and mutational analysis. Polymorphism in the mitochondrial cyt b gene helps in studying the biodiversity and is a valuable tool for the identification of species. Mutations in the cyt b gene produce abnormal protein leading to deficiencies in the complex III (coenzyme Q), resulting in defective oxidative phosphorylation and consequently effects other metabolic pathways. In the present article, we comprehensively compare the biodiversity of cyt b in bc1 and b6f complexes using in silico structural analysis tools, emphasizing that despite vast knowledge available in this field, still there are so much to explore about cyt b.
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