May play a role in magnetite crystal maturation (Probable). May transfer electrons to balance the Fe(2+)-Fe(3+) ratio during magnetite formation (Probable). Probably binds 2 heme groups via the 2 magnetochrome (MCR) motifs. Part of the probable 18 gene mamAB operon. Cells have a weak magnetic response and make magnetosome membranes. Magnetosomes are about half the size of wild-type, but nearly as numerous (PubMed:20212111). Deletion of this gene with amb1002 to amb1007 give smaller, elongated magnetite crystals, does not alter subcellular localization of MamC, MamF, MamI or MmsF (PubMed:25775527). Deletion of genes mamH to mamV (amb0961 to amb0978) gives cells with no magnetosomes and no magnetic response (PubMed:20212111). 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)). Expression of just the minimal mamAB gene cluster (amb0961 to amb0978), including this gene, is sufficient to form a minimal magnetosome chain with small magnetite particles. Belongs to the magnetosome MamT family.