Flavocytochrome c sulfide dehydrogenase explained

Sulfide-cytochrome-c reductase (flavocytochrome c)
Ec Number:	1.8.2.3

Symbol:	FCSD-flav_bind
Flavocytochrome c sulfide dehydrogenase, flavin-binding
Pfam:	PF09242
Interpro:	IPR015323
Scop:	1fcd

Flavocytochrome c sulfide dehydrogenase, also known as Sulfide-cytochrome-c reductase (flavocytochrome c), is an enzyme with systematic name hydrogen-sulfide:flavocytochrome c oxidoreductase.^{[1] [2] [3] [4] [5]} It is found in sulfur-oxidising bacteria such as the purple phototrophic bacteria Allochromatium vinosum.^{[6] [7]} This enzyme catalyses the following chemical reaction:

hydrogen sulfide + 2 ferricytochrome c

\rightleftharpoons sulfur + 2 ferrocytochrome c + 2 H⁺

These enzymes are heterodimers of a flavoprotein (fccB) and a diheme cytochrome (fccA;) that carry out hydrogen sulfide-dependent cytochrome C reduction. The diheme cytochrome folds into two domains, each of which resembles mitochondrial cytochrome c, with the two haem groups bound to the interior of the subunit. The flavoprotein subunit has a glutathione reductase-like fold consisting of a beta(3,4)-alpha(3) core, and an alpha+beta sandwich. The active site of the flavoprotein subunit contains a catalytically important disulfide bridge located above the pyrimidine portion of the flavin ring. The flavoprotein contains a C-terminal domain required for binding to flavin, and subsequent electron transfer.^[6] Electrons are transferred from the flavin to one of the haem groups in the cytochrome. Both FAD and heme C are covalently bound to the protein.

Notes and References

1. Kusai K, Yamanaka T . The oxidation mechanisms of thiosulphate and sulphide in Chlorobium thiosulphatophilum: roles of cytochrome c-551 and cytochrome c-553 . Biochimica et Biophysica Acta (BBA) - Bioenergetics . 325 . 2 . 304–14 . November 1973 . 4357558 . 10.1016/0005-2728(73)90106-0 .
2. Fukumori Y, Yamanaka T . Flavocytochrome c of Chromatium vinosum. Some enzymatic properties and subunit structure . Journal of Biochemistry . 85 . 6 . 1405–14 . June 1979 . 10.1093/oxfordjournals.jbchem.a132467 . 222744 .
3. Sorokin DY, Gray GO, Gaul DF, Knaff DB . Partial purification and characterization of two soluble c-type cytochromes from Chromatium vinosum . Archives of Biochemistry and Biophysics . 222 . 1 . 78–86 . April 1983 . 6301383 . 10.1016/0003-9861(83)90504-0 .
4. de Jong GA, Robertson LA, Kuenen GJ . Purification and characterization of sulfide dehydrogenase from alkaliphilic chemolithoautotrophic sulfur-oxidizing bacteria . FEBS Letters . 427 . 1 . 11–4 . May 1998 . 9613590 . 10.1016/S0014-5793(98)00379-2 . 2818096 . free .
5. Kostanjevecki V, Brigé A, Meyer TE, Cusanovich MA, Guisez Y, van Beeumen J . A membrane-bound flavocytochrome c-sulfide dehydrogenase from the purple phototrophic sulfur bacterium Ectothiorhodospira vacuolata . Journal of Bacteriology . 182 . 11 . 3097–103 . June 2000 . 10809687 . 94494 . 10.1128/jb.182.11.3097-3103.2000 .
6. Chen ZW, Koh M, Van Driessche G, Van Beeumen JJ, Bartsch RG, Meyer TE, Cusanovich MA, Mathews FS . The structure of flavocytochrome c sulfide dehydrogenase from a purple phototrophic bacterium . Science . 266 . 5184 . 430–2 . October 1994 . 7939681 . 10.1126/science.7939681. 1994Sci...266..430C .
7. Quentmeier A, Hellwig P, Bardischewsky F, Wichmann R, Friedrich CG . Sulfide dehydrogenase activity of the monomeric flavoprotein SoxF of Paracoccus pantotrophus . Biochemistry . 43 . 46 . 14696–703 . November 2004 . 15544340 . 10.1021/bi048568y .