<p>Succinate dehydrogenase (SDH) is a membrane-bound complex of two main components: a membrane-extrinsic component composed of an FAD-binding flavoprotein and an iron-sulphur protein, and a hydrophobic component composed of a cytochrome b and a membrane anchor protein. The cytochrome b component is a mono-haem transmembrane protein [<cite idref="PUB00002750"/>, <cite idref="PUB00003763"/>, <cite idref="PUB00003349"/>] belonging to a family that includes:</p><p> <ul><li>Cytochrome b-556 from bacterial SDH (gene sdhC).</li><li>Cytochrome b560 from the mammalian mitochondrial SDH complex, which is encoded in the mitochondrial genome of some algae and in the plant <taxon tax_id="3197">Marchantia polymorpha</taxon>.</li><li>Cytochrome b from yeast mitochondrial SDH complex (gene SDH3 or CYB3).</li><li>Protein cyt-1 from <taxon tax_id="6239">Caenorhabditis elegans</taxon>.</li></ul> </p><p> These cytochromes are proteins of about 130 residues that comprise three transmembrane regions. There are two conserved histidines which may be involved in binding the haem group.</p> Succinate dehydrogenase, cytochrome b subunit, conserved site