Production of a Protein (Enzyme, Antibody, Protein A)-Magnetite Complex by Genetically Engineered Magnetic Bacteria Magnetospirillum Sp. AMB-1

Abstract

Magnetospirillum sp. AMB-1 is a magnetic bacterium which synthesizes intracellular particles of magnetite (Fe3O4). A genomic DNA fragment required for the synthesis of magnetic particles was previously isolated from this strain. The complete nucleotide sequence of this fragment has been determined by us. An open reading frame (ORF), designated magA, encodes a polypeptide which represents an iron transport protein. Intracellular localization of the MagA protein was studied using magA—luc fusion proteins. The luc gene was cloned downstream of the magA hydrophilic C-terminal domain. The fusion protein was detected on the surface of the lipid bilayer covering the magnetic particles. The MagA protein on the bacterial magnetic particle (BMP) was detected by immunoassay using an anti-luciferase antibody. The N- and C-termini of MagA protein were found outside the BMP membrane. These results show the utility of magA fusions for detecting multi functional proteins on BMP. Recombinant protein-BMP complex production has been carried out using the fed-batch culture by adding nitric acid and succinate as nitrogen and carbon source.