The magnetosome membrane protein Mms6 produces MR contrast in vitro

Introduction Magnetotactic bacteria are able to orient themselves along the Earth’s magnetic field lines using specialized membrane-bound organelles called magnetosomes that contain iron oxide crystals. The genomes of these species are of great interest for molecular imaging as magnetosomes can also function as contrast agents for MR imaging [1]. It has been shown that the expression of a single gene present in magnetotactic bacteria, magA, may produce sufficient contrast for cellular imaging [2, 3]. Another protein, Mms6, is thought to initiate magnetite crystal nucleation within the magnetosome [4]. Mms6 has been found to be bound to bacterial magnetite [4] and to regulate crystal size and shape [5]. These biominerization functions may be especially important for image contrast applications where the magnetization and relaxivity changes induced by the reporter genes must be maximized. We hypothesize that once the Mms6 gene, mms6, is transfected and expressed in mammalian cells, it will function as a reporter gene producing iron oxide crystals that can be visualized with MRI.