Required for correct biomineralization of the magnetosome; probably converts and then transports some form of iron. It is partially functionally redundant with MamH. May function with MamX, MamY amd Mms6. Tagged protein forms straight lines with a punctate pattern extending along most of the cell associated with its inner curvature, in the correct position to be associated with magnetosomes, but longer than the usual chain. This bacteria makes up to 20 cubo-octahedral magnetosomes of about 45 nm in diameter which contain membrane-bound crystals of magnetite (Fe(3)O(4)). In the N-terminal section; belongs to the major facilitator superfamily.