Promotes the formation of magnetite in Fe(2+)-rich conditions, when magnetite is not readily formed. Binds both Fe(2+) and Fe(3+). May help control the production of crystals with a specific morphology (By similarity). May function with MamX, MamY amd MamZ in biomineralization (Probable). The 4 genes of this operon collectively influence magnetosome size and number (PubMed:24816605). Full length protein oligomerizes and interacts with MamA. Low levels of protein are associated with magnetosomes as they start to develop, rises to a maximum as the magnetosomes mature and then decreases (at protein level) (PubMed:30367002). Part of the probable mms6 operon (Probable). The C-terminal 21 residues (later called magnetite-interacting component, MIC, residues 112-133) self assemble into multimers up to octamers; this fragment binds Fe(3+) which alters its structure. Also binds Fe(2+). May undergo cleavage. Normal magnetic response, slightly fewer, slightly smaller magnetosomes. A double mms6-mmsF deletion has an intermediate magnetic response, with slightly smaller and fewer magnetosomes than the single mutation (PubMed:24816605). Deletion of the 4 gene operon (mms6, mmsF, mms36 and mms48) gives an intermediate magnetic response with fewer, smaller magnetosomes in irregular pseudo-chains (PubMed:22043287, PubMed:24816605). Deletion of approximately 80 kb of DNA, including this gene, 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)). Belongs to the magnetosome Mms6 family. Extended N-terminus.