Structural Classification of Proteins

Fold: Heme-binding four-helical bundle

: core: four transmembrane helices, up-and-down bundle, binds one or two heme groups in between the helices

Lineage:

Root: scop
Class: Membrane and cell surface proteins and peptides [56835]
Does not include proteins in the immune system
Fold: Heme-binding four-helical bundle [81344]
core: four transmembrane helices, up-and-down bundle, binds one or two heme groups in between the helices

Transmembrane di-heme cytochromes [81342] (2)
Three of the four heme-ligands are conserved between the two families; both heme groups bind similarly but not identically
uperfamily
1. Cytochrome b of cytochrome bc1 complex (Ubiquinol-cytochrome c reductase) [81642] (5)
  a part (domain) of a larger mitochondrial cytochrome b subunit, separate subunit in plants and cyanobacteria
2. Formate dehydrogenase N, cytochrome (gamma) subunit [75645] (1)
Respiratory nitrate reductase 1 gamma chain [103501] (1)
possible link between the two other superfamilies: this subunit corresponds to the gamma subunit of a functionally related Formate dehydrogenase N complex but is structurally closer to the Fumarate reductase subunit FrdC
uperfamily
1. Respiratory nitrate reductase 1 gamma chain [103502] (1)
Fumarate reductase respiratory complex transmembrane subunits [81343] (2)
two distinct families: in one family the common fold is contained in a single-chain subunit, in the other it is formed by two chains
uperfamily
1. Fumarate reductase respiratory complex cytochrome b subunit, FrdC [56910] (1)
  duplication: consists of two structural repeats; the heme-binding sites are related by pseudo two fold symmetry
2. Succinate dehydrogenase/Fumarate reductase transmembrane subunits (SdhC/FrdC and SdhD/FrdD) [81373] (4)
  consists of two homologous non-identical subunits that form a heterodimer; may or may not contain heme groups