Cytochrome c Conclusions

The preceding discussion of cytochromes c provides most detail on eukaryotic, mitchondrial cytochromes c, a small subset of this huge superfamily. Additionally, all the cytochromes c discussed in this section envelop one heme cofactor, although many cytochromes in nature contain more than one heme cofactor. Many other redox proteins contain a cytochrome c domain—a few of these mentioned here include the cytochrome bci complex discussed in Section 7.6, cytochrome c oxidase to be discussed in Section 7.8, and cytochrome c peroxidase, discussed briefly in Section 7.7 (see especially Section 7.7.4.2). 

Cytochrome c folding and electron transfer are related topics. An improperly folded protein—engendered through amino acid mutation for instance— will exhibit diminished or nonexistent electron transfer. More reports will be forthcoming from many research groups on the topics of protein folding and electron transfer between proteins. The reader should consult the literature for updates on these related hot topics. The reader is referred to the 2006 Chemical Reviews article from the Bertini group (reference 101), which exhaustively surveys the cytochrome c field. 

Cytochrome c and ubiquinol oxidases are part of an enzyme superfamily coupling oxidation of ferrocytochrome c (in eukaryotes) and ubiquinol (in prokaryotes) to the 4 e /4 reduction of molecular oxygen to H2O. After this introduction, we will concentrate on the cytochrome c oxidase enzyme. The two enzymes, cytochrome c oxidase (CcO) and ubiquinol oxidase, are usually defined by two criteria (1) The largest protein subunit (subunit I) possesses a high degree of primary sequence similarity across many species (2) members possess a unique bimetallic center composed of a high-spin Fe(II)/(III) heme in close proximity to a copper ion. Cytochrome c oxidase (CcO) is the terminal 

Cytochrome c oxidase (CcO) has been characterized as a proton pump (see, for instance, M. Saratse s 1999 Science magazine article ), although CcO 

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