c-Type cytochrome biogenesis can occur via a natural Ccm system lacking CcmH, CcmG, and the heme-binding histidine of CcmE (Journal of Biological Chemistry (2010) 285, (22882-22889))
Goddard AD., Stevens JM., Rao F., Mavridou DAI., Chan W., Richardson DJ., Allen JWA., Ferguson SJ.