Forms a complex with CCMFC, CCMFN1 and CCMH that performs the assembly of heme with c-type apocytochromes in mitochondria. Interacts with CCMFC, CCMFN1, CCMH and CYTC-1. 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 this duplicated gene (At2g07768) 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. Ref.1 indicates that this sequence represents the C-terminal part of a protein produced after trans-splicing. No experimental data confirms this assertion.