Plays a role in biomineralization; might regulate pH in the magnetosome. Part of the probable 17 gene mamAB operon. Weak magnetic response, very few, small magnetite-containing magnetosomes. Near wild-type localization of MamC (PubMed:24816605). Magnetosome vesicles are approximately wild-type in size, shape and chain-like alignment, only a few have crystals (PubMed:27286560). Deletion of approximately 80 kb of DNA, including this operon, leads to cells that are non-magnetic, lack internal membrane systems, grow poorly, have reduced mobility and take-up and accumulate iron poorly (PubMed:13129949). This bacteria makes up to 60 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 (MGMSRv2__2365 to MGMSRv2__2381), including this gene, is sufficient to form a minimal magnetosome chain with small magnetite particles. Belongs to the arsenite-antimonite (ArsB) efflux (TC 2.A.45) family.