Cytochrome c 7

Cytocrhome c 7 (Cc7) is a three heme-containing protein derived from the sulfur-reducing bacterium Desulfuromonas acetoxidans. Cc7 is crucial to the bacteria's anaerobic sulfure respiration as it plays a role in the electron-transfer mechanism, and as such it is located in the mitochondrial intermembrane space^[1]. Over the course of 3.5 million years, Desulfuromonas acetoxidans have evolved to use anaerobic sulfure respiration as the main driving force of their survival^[2]. As a result, Cc7 is able to reduce sulfure, its oxidized variants (thiosulfate, sulfur, sulfite, sulfate, etc) and even heavy metals to produce the required energy^[3]. If using sulfure, the product formed is hydrogen sulfide. This compound is able to react with heavy metal ions to form almost non-lethal and quite insoluble metal sulfides^[4]. This enzymatic ability of Cc7 is unique to the animal kingdom, and the ability to create less-toxic and insoluble metal sulfides has intrigued researchers as of late^[5]. By harnessing Desulfuromonas acetoxidans and its Cc7 protein, researchers hope to create possible applications to use these bacteria to decontaminate environments polluted with toxic heavy metals from industrial wastes across the globe. And because of the metal sulfides insolubility, removing them from the environment will be simpler and cheaper than current heavy metal toxic waste filtration operations^[6].

Structural Components

Cc7 is a single polypeptide chain 68 residues total containing three heme groups. The polypeptide strand has one alpha helix 4 residues in length and two beta strands 2 residues in length. The heme groups are labelled as I, III, and IV,

Function

The function of Cc7 was determined by using NMR spectroscopy as a mointoring technique to determine the oxidation levels of the protein as more chromate (-2) - Cite error: Invalid <ref> tag; refs with no name must have content. - Chromate (-2) nor chromium are part of Cc7's structure; they are the reactant and the product of the reductase activity of Cc7, respectively. The following steps will elaborate how Cc7 carries out its oxidation.

As mentioned previously, Cc7 is a sulfur/metal terminal reductase, an enzyme that reduces a sulfur-containing compounds into a sulfide or reduces heavy metals to generate electrons to be used in electron transport chain

- Cite error: Invalid <ref> tag; refs with no name must have content. - To begin thus reaction, Cc7 must be in its resting state (i.e. fully reduced). Chromate(-2) (an oxidized heavy metal) .

The products of the reaction are chromium(III) and the oxidized protein with three iron(III) hemes.

Structural highlights

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