Magnetotactic bacteria (MTB) can navigate through the Earth’s magnetic field. These bacteria synthesize organelles called "magnetosomes", which contain a magnetic nanoparticle of magnetite (Fe3O4) or greigit (Fe3S4) and are surrounded by a lipid membrane. It was shown that magnetosome membrane contains a unique set of proteins that are thought to direct the biomineralization of magnetite crystals. In MTB, most of the magnetosome formation involves genes that are located in the genomic magnetosome island (MAI). One of the proteins involved in the biomineralization of magnetite crystals is an integral membrane protein. It is a small protein (~12kDa) with two transmemebrane helices. To understand its function, we attached its magnetosomal loop (located between H1 to H2) onto the C-terminal of MBP (maltose binding protein). By using X-ray crystallography, we determined the MBP-loop structure from magnetotactic bacteria to a resolution of 2.8 A. it also shown that it can interact with the magnetite particle using Isothermal Titration Calorimetry (ITC) and effect magnetite crystals size and shape during iron precipitation In Vitro. Based on our results, we identified a possible patch which may be important for the biomineralization of magnetite and used this structure to predict homologous proteins from other MTB species.
