Forms a complex with CCMFC, CCMFN2 and CCMH that performs the assembly of heme with c-type apocytochromes in mitochondria. Interacts with CCMFN2 and CCMH. A stretch of 270 kb of the mitochondrial genome is duplicated within the centromere of chromosome 2 resulting in the duplication of the gene. The expression of the duplicated gene (At2g07783) is not demonstrated. It is also probably not RNA edited and therefore differs in all the positions known to be edited. Belongs to the CcmF/CycK/Ccl1/NrfE/CcsA family. Its N-terminal part is produced after trans-splicing. No experimental data confirms this assertion.