Fumarate reductase type B, transmembrane subunit (IPR004224)

Short name: Fum_red_B_TM

Overlapping homologous superfamilies

Family relationships


Quinol:fumarate reductase (QFR) couples the reduction of fumarate to succinate to the oxidation of quinol to quinone, the opposite reaction to that catalyzed by the related protein, succinate:quinone oxidoreductase (SQR). QFR and SQR complexes are collectively referred to as succinate:quinone oxidoreductases and are predicted to share similar structures, containing either 3 or 4 subunits [PMID: 10586875].

Subunit A (the flavoprotein subunit) contains the site of fumarate reduction and a covalently bound flavin adenine dinucleotide prosthetic group. Subunit B (the iron protein subunit) contains three iron-sulphur centres. Subunit(s) C (and D) (the membrane anchor subunits or cytochrome b subunits) include the membrane-spanning segments and binds haem b molecules [PMID: 10586875]. The composition of these hydrophobic, cytochrome B subunits varies depending on the enzyme subtype. Type A have two polypeptides, with three transmembrane helices each, and contain two protoheme IX molecules (denoted heme bH and heme bL). Type B have one polypeptide with five transmembrane helices and contain heme bH and heme bL. Type C have the same polypeptide arrangement as Type A, but contains only one protoheme IX molecule, corresponding to heme bH. Type D have two polypeptides, with three transmembrane helices each, and are without heme [PMID: 9210286].

This family refers to subunit C (the cytochrome B subunit) of type B fumarate reductases.

GO terms

Biological Process

GO:0006099 tricarboxylic acid cycle

Molecular Function

No terms assigned in this category.

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.