Heme lyase (NrfEFG) for insertion of heme into c552, subunit NrfE; May be required for the biogenesis of c-type cytochromes. Possible subunit of a heme lyase.

Heme lyase, CcmF subunit; Required for the biogenesis of c-type cytochromes. Possible subunit of a heme lyase.

Nitrite reductase, formate-dependent, penta-heme cytochrome c; Plays a role in nitrite reduction.

Periplasmic thioredoxin of cytochrome c-type biogenesis; Involved in disulfide bond formation. Catalyzes a late, reductive step in the assembly of periplasmic c-type cytochromes, probably the reduction of disulfide bonds of the apocytochrome c to allow covalent linkage with the heme. Possible subunit of a heme lyase. DsbE is maintained in a reduced state by DsbD.

Nitrite reductase, formate-dependent, cytochrome; Catalyzes the reduction of nitrite to ammonia, consuming six electrons in the process. Has very low activity toward hydroxylamine. Has even lower activity toward sulfite. Sulfite reductase activity is maximal at neutral pH (By similarity).

Heme export ABC transporter permease; Required for the export of heme to the periplasm for the biogenesis of c-type cytochromes.

Periplasmic heme chaperone; Heme chaperone required for the biogenesis of c-type cytochromes. Transiently binds heme delivered by CcmC and transfers the heme to apo-cytochromes in a process facilitated by CcmF and CcmH; Belongs to the CcmE/CycJ family.

Formate-dependent nitrite reductase, membrane subunit; Probably involved in the transfer of electrons from the quinone pool to the type-c cytochromes; Belongs to the NrfD family.

Heme export ABC transporter ATPase; Part of the ABC transporter complex CcmAB involved in the biogenesis of c-type cytochromes; once thought to export heme, this seems not to be the case, but its exact role is uncertain. Responsible for energy coupling to the transport system.