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 (By similarity). ATP + H2O + heme b(in) = ADP + H(+) + heme b(out) + phosphate The complex is composed of two ATP-binding proteins (CcmA) and two transmembrane proteins (ccmB). Belongs to the ABC transporter superfamily. CcmA exporter (TC 3.A.1.107) family.