Role of the magnetosome proteins MamGFDC in biomineralization and size control of magnetite crystals in Magnetospirillum gryphiswaldense

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Bacterial magnetosomes are unique prokaryotic organelles consisting of membrane-bounded magnetite nanocrystals that are synthesized for magnetic navigation. One major unsolved question is how magnetosome biomineralization is precisely regulated to achieve the structural perfection, characteristic shapes and uniform sizes of magnetite nanocrystals. The abundant magnetosome-associated MamGFDC proteins in the bacterium Magnetospirillum gryphiswaldense represent the first biological determinants implicated in size control of magnetosomes, although their precise functions are still unknown. We will characterize MamGFDC and the related MmsF protein and elucidate the mechanism by which they interfere with magnetite biomineralization. By genetic analysis we will estimate their individual contributions to size control. Controlled mamGFDC expression will then be used for the synthesis of size-modified magnetic nanoparticles. The intracellular localization and interaction of wild-type and mutant proteins will be studied by biochemical methods and fluorescence microscopy. The potential to bind magnetite and to directly interfere with its crystallization will be assessed in vitro. Our studies may facilitate the biogenic synthesis of tailored magnetic nanoparticles for biotechnological applications and may also contribute to an improved understanding of biomolecular interactions at the organic/inorganic interface of iron biominerals.