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
Superfamily: Transmembrane di-heme cytochromes [81342]
Three of the four heme-ligands are conserved between the two families; both heme groups bind similarly but not identically uperfamily
Mitochondrial cytochrome b subunit, N-terminal domain [81641]
also includes extra transmembrane (linker) helix absent in plants and cyanobacteria subunits
uperfamily
