Promotes the formation of magnetite in Fe(2+)-rich conditions, when magnetite is not readily formed (PubMed:27112228). Binds Fe(3+) and Fe(2+) (PubMed:12496282, PubMed:23857056, PubMed:27112228) (Probable). May play a role in nucleation of magnetite crystal formation (Probable) (PubMed:22716969). May help control production of crystals with a specific morphology (Probable) (PubMed:22716969, PubMed:27759096). Greatly improves the formation of magnetosome-like magnetite crystals in vitro (PubMed:12496282). Isolated short protein, probably residues 75-133, binds up to 18 Fe(3+) per monomer and self-assembles into micelles about 21-26 nm in diameter; the C-terminal 21 residues also self-assemble (PubMed:23857056). Full length protein oligomerizes (PubMed:28955887). Full-length protein interacts with MamA (PubMed:28955887). Tightly associated with magnetite crystals (PubMed:12496282). 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. Under aerobic conditions, when magnetites cannot form, or in the absence of iron, the protein is dispersed in the cell, probably in the inner membrane; as magnetosomes form tagged Mms6 localizes in a line that corresponds to the position of magnetite crystals (PubMed:27481925). Short protein seems to localize specifically to magnetosomes which have magnetite crystals (Probable). Fe(3+) binding by the shorter form (residues 75-133) is inhibited by Ca(2+) and Mg(2+) (PubMed:12496282). The C-terminal 21 residues (magnetite-interacting component, MIC, residues 112-133) self assemble into multimers up to octamers; this fragment binds Fe(3+) which alters its structure (PubMed:23857056). Another paper showed binding of MIC to Fe(2+) via Asp-123, Glu-124, Glu-125, and Glu-127 with a minor contribution from Glu-118 (PubMed:27112228). The isolated lumenal MIC binds Fe(2+) and Ni(2+), Ni(2+)-binding may not be physiological; in this paper binding to Fe(3+) was poor. Although it binds iron the protein fragment has no effect on magnetite crystal formation in an iron co-precipitation experiment, however mutating some of its residues decreases crystal size (PubMed:30405554). Correct subcellular location to the magnetosomes requires the N-terminal 75 residues (PubMed:27481925). Seen in gels as a band of about 6 kDa which has residue 75 as its N-terminus, suggesting it may undergo cleavage (Probable). 2 forms, a full-length and the shorter protein are both detected immunologically in magnetosomes (PubMed:28955887). No effect on bacterial growth. Magnetosomes are wild-type in number and size, but slightly less regularly spaced. Magnetite crystals are smaller, irregularly shaped instead of cubooctahedral, crystal growth may be incomplete. Magnetite-associated proteins Mms5, MamC and MamD levels are significantly decreased (PubMed:21169637). Single non-polar gene mutation has a slightly reduced magnetic response, crystals are smaller and elongated (PubMed:22716969, PubMed:27759096). Magnetite crystals are elongated and their surface structure is altered, iron uptake is wild-type (PubMed:24961165). Deletion of the probable mms6 operon (amb0955, mms6 and mmsF) leads to weak magnetic response and much smaller, elongated magnetite crystals (PubMed:22716969). Transfection of a codon optimized gene into human adipose-derived stem cells yields cells with magnetic crystals; the crystals do not have a noticeable effect on cell proliferation, migration or differentiation. A fusion of MIC to barstar (an RNase inhibitor from B.amyloliquefaciens) binds and stabilizes coprecipitated magnetite nanoparticles for at least 2 months. Cells transfected with barnase (the ribonuclease target of barstar) can be specifically targeted by magnetite-bound barstar which could be used in cell-specific cancer treatment. 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)). Belongs to the magnetosome Mms6 family. PMID:21169637 identified the deleted gene as YP_420381.1 (equivalent to amb1018, mamY), which does not correspond to either the gene or protein sequenced by the same authors. It is not clear which gene was really deleted. Extended N-terminus.