Required for synthesis of single-domain magnetite particles and magnetosomes, especially in the absence of nitrate. Forms filaments, which form bundles in the presence of GTP. Has both GTPase and ATPase activity; GTPase is 2.5 time more efficient. Has no activity on CTP or TTP (PubMed:20023033). May be involved in redox control for magnetite crystallization (Probable). Mild overexpression causes cell elongation (PubMed:24272781). May recruit other proteins (MamX, MamY and MamZ and possibly Mms6) to a complex required for biomineralization (Probable). GTP + H2O = GDP + H(+) + phosphate ATP + H2O = ADP + H(+) + phosphate Interacts with FtsZ (Probable). Probably interacts with MamX and MamY (PubMed:30367002). Upon mild overexpression assembles into foci at midcell and at cell poles, foci colocalize with FtsZ but not with MamK filaments. Subcellular location is independent of other magnetosome locus encoded proteins, but may depend on FtsZ (PubMed:24272781). A similar construct shows a dispersed location at 6 hours post-induction and a dot-like distribution at 18 hours post-induction (PubMed:30367002). Expressed in exponential phase, peaks about 18 hours (PubMed:20023033, PubMed:24020498). Fourth gene in the 4 gene mamXY operon (PubMed:20023033) (Probable). Not essential for cell growth. When grown in NH(4)Cl medium loss of magnetic response. Magnetosomes are much smaller with poorly defined morphology, poor crystallization and are irregularly distributed with large gaps. They are wild-type in number, are magnetite but predominantly superparamagnetic instead of single-domain (PubMed:20023033). When grown in NO(3-), nitrate, single deletion cells are nearly wild-type; in this study NH(4)Cl-grown single deletion cells make a few wild-type magnetosomes in addition to poor crystals in chains, i.e. the phenotype is not as extreme as in the previous study (PubMed:24272781). Deletion of 4 consecutive genes (mamY, mamX, mamZ, ftsZm) leads to cells with an intermediate magnetic response where magnetosomes have short chains of nearly regularly shaped, cubo-octahedral crystals flanked by small particles with poorly defined morphologies (PubMed:22043287). 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 FtsZ family.