Biomagnetic nanoparticle formation and application

Magnetospirillum sp. AMB-1 is a bacterium that synthesizes intracellular particles of magnetite (Fe₃O₄). A magA gene required for the synthesis of bacterial magnetic particles (BMPs) was isolated from this strain and its gene product (MagA protein) was characterized as an iron transport protein. Intracellular localization analysis of the MagA protein using magA–Luc fusion proteins showed that MagA protein is localized on the surface of the lipid bilayer covering the BMPs. One particular BMP-associated protein, designated MpsA, was also purified from this strain and characterized. By the fusion-protein method using mpsA-luc genes, it was demonstrated that Mps-protein is preferentially partitioned onto the BMP membrane. Furthermore, application of BMPs to immunoassay is also described.