Biosynthesis of Functional Protein-Magnetic Nanoparticle Complexes with Microorganisms

Abstract

Magnetotactic bacteria synthesize nano-sized magnetic particles in the cells. The bacterial magnetic particles have a core of magnetite (Fe₃O₄), and are surrounded by a lipid bilayer membrane containing a number of proteins. Since the genetic engineering methodology for magnetotactic bacteria was established, production of recombinant proteins has successfully been performed in which the native proteins in the lipid membrane can serve as anchors for the protein display. These advantages lead to creation of a variety of magnetic particles displaying functional proteins. In this review article, after describing the basic strategy for a protein display on bacterial magnetic particles, we introduce our recent efforts in order to express recombinant proteins, including membrane proteins and disulfide-bonded proteins, which the basic approach cannot match. Due to these efforts, tetracycline-inducible expression system, protease- and anchor protein-deletion mutants, as well as the “in vitro docking method” have been established. The novel systems have shown considerable promise for improving the display efficiency of the difficult-to-express proteins, and thus are expected to contribute to further development of functional magnetic particles.