Causes tubulation when added to magnetosome-derived liposomes, binds liposomes; may be involved in constriction of the cell inner membrane to form mature magnetosomes (PubMed:20345667). Binds preferentially to cardiolipin, a component of bacterial membranes, with very poor to no binding of other tested (phospho)lipids. Addition of cardiolipin to magnetosome-derived lipids increases tubulation (PubMed:30039923). May function with MamX, MamZ amd Mms6 (By similarity). Primarily associated with immature magnetosomes with small magnetite crystals, but longer than the usual magnetosome chain. No growth phenotype, retains a magnetic response. Magnetosome vesicles are slightly bigger than wild-type while magnetite crystals are equal in number but have a much wider size range. 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 MamY family.