InterPro domain: IPR002541

This domain is found in various proteins involved in cytochrome cassembly from mitochondria, chloroplast and bacteria; including among others CycK from Rhizobium leguminosarum [ 1 ], CcmC and CcmF from Escherichia coli [ 2 ], CcsA from Chlamydomonas [ 3 ], and orf240 from Triticum aestivum (wheat) mitochondria [ 4 ].

CcmC interacts directly with heme, and it is the only protein of the ccm operon that is strictly required for heme transfer [ 5 ]. CcmF contains a b-type heme and is thought to be a cytochrome c synthetase [ 6 ]. CcsA is required during biogenesis of c-type cytochromes at the step of heme attachment [ 7 ]. R. leguminosarum CycK and wheat orf240 also contain a putative heme-binding motif [ 7 , 7 ].

1. Characterization of the cycHJKL genes involved in cytochrome c biogenesis and symbiotic nitrogen fixation in Rhizobium leguminosarum. J. Bacteriol. 177, 4927-34
2. Escherichia coli genes required for cytochrome c maturation. J. Bacteriol. 177, 4321-6
3. The plastid-encoded ccsA gene is required for heme attachment to chloroplast c-type cytochromes. J. Biol. Chem. 271, 4632-9
4. A gene proposed to encode a transmembrane domain of an ABC transporter is expressed in wheat mitochondria. Mol. Gen. Genet. 246, 91-9
5. Heme transfer to the heme chaperone CcmE during cytochrome c maturation requires the CcmC protein, which may function independently of the ABC-transporter CcmAB. Proc. Natl. Acad. Sci. U.S.A. 96, 6462-7
6. Heme ligand identification and redox properties of the cytochrome c synthetase, CcmF. Biochemistry 50, 10974-85