Involved in magnetite crystal maturation, but not in magnetosome vesicle tubulation or formation. One of 7 genes (mamLQBIEMO) able to induce magnetosome membrane biogenesis; coexpression of mamLQRBIEMO in a deletion of the 17 gene mamAB operon restores magnetosome vesicle formation but not magnetite biosynthesis. Tagged protein forms chains, aligned patches but also unaligned patches in the cell; the chains and aligned patches are in the correct position to be magnetosomes. Part of the probable 17 gene mamAB operon. No magnetic response, no magnetosomes, no iron crystals of any sort. MamC is mislocalized in a few punctate spots throughout the cell (PubMed:24816605). No magnetic response at 30 degrees Celsius, a weak response at lower temperature. At 30 degrees Celsius magnetosome vesicles are smaller, sometimes align in a chain with the filament, only a few have very small crystals. Other, possibly precursor magnetosome vesicles are visible. MamC and MamI mislocalized to 1 to a few patches in most cells (PubMed:27286560). Deletion of 3 consecutive genes (mamJ, mamK, mamL) leads to cells devoid of magnetosomes or a magnetic response (PubMed:22043287). 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 MamL family. Extended N-terminus. Extended N-terminus. Extended N-terminus.