The protein SO_1778 (MtrC) of Shewanella oneidensis MR-1, and its paralog SO_1779 (OmcA), with which it intteracts, are large decaheme proteins, about 900 amino acids in length, involved in the use of manganese [Mn(III/IV)] and iron [Fe(III)] as terminal electron acceptors. This model represents these and similar decaheme proteins, found also in Rhodoferax ferrireducens DSM 15236, Aeromonas hydrophila ATCC7966, and a few other bacterial species. [Energy metabolism, Electron transport]