Involved in redox-control of magnetite formation (By similarity). Oxidizes Fe(2+) at alkaline pH; successively forms ferrihydrite (Fe(3+)(2)O(3) 0.5 H(2)O) then magnetite (Fe(3)O(4)) from an Fe(2+) solution (By similarity). Binds 2 heme groups via the magnetochrome (MCR) motifs. Homodimer. Not seen in magnetosome membranes. Part of the probable 17 gene mamAB operon. The dimer forms a pocket of about 8 X 15 Angstroms, lined with acidic residues, which may bind 2 Fe(2+) ions. Subject to proteolytic cleavage which requires both MamE and MamO. Intermediate magnetic response, few large magnetosomes with magnetite, makes many very small, irregular hematite crystals. Near wild-type localization of MamC (PubMed:24816605). 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 magnetosome MamP family.