FAM210B directly interacts with terminal heme synthesis enzymes but does not with MFRN1 (Slc25a37).
A, immunoprecipitation of co-expressed FAM210B-HA and FLAG-MFRN1 demonstrates FAM210B does not directly interact with MFRN1. B, FAM210B-HA interacts with the terminal enzymes of the heme synthesis pathway, PPOX and FECH, but not CPOX. MFRN1, CPOX, PPOX, and FECH are all localized to the mitochondrial inner membrane. C, immunoprecipitation of FAM-210B FLAG stably expressed in differentiating MEL cells shows that ectopically expressed FAM210B interacts with endogenous FECH. D, FAM210B-HA and FAM210B-FLAG do not interact, demonstrating that FAM210B does not homooligomerize. E, model of the role of FAM210B as an adaptor protein in an oligomeric complex with terminal heme enzymes, required for terminal erythropoiesis and mitochondrial iron importation.