Dihaem cytochrome c (DHC) is a soluble c-type cytochrome that folds into two distinct domains, each binding a single haem group and connected by a small linker region. Despite little sequence similarity, the N-terminal domain (residues 12-75) is a class I type cytochrome c, that binds one of the haems, but the domain surrounding the other haem is structurally unique. DHC binds electrostatically to an oxygen-binding protein, sphaeroides haem protein (SHP), as a component of a conserved electron transfer pathway. DHC acts as the physiological electron donor for SHP during phototrophic growth [1]. In certain species DHC is found upstream of Pfam:PF01292.

1: Structural and functional studies on DHC, the diheme cytochrome c from Rhodobacter sphaeroides, and its interaction with SHP, the sphaeroides heme protein. Gibson HR, Mowat CG, Miles CS, Li BR, Leys D, Reid GA, Chapman SK; Biochemistry. 2006;45:6363-6371. PMID:16700547