Subcellular localization of the magnetosome protein MamC in the marine magnetotactic bacterium Magnetococcus marinus strain MC-1 using immunoelectron microscopy
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Magnetotactic bacteria are a diverse group of prokaryotes that biomineralize intracellular magnetosomes, composed of magnetic (Fe3O4) crystals each enveloped by a lipid bilayer membrane that contains proteins not found in other parts of the cell. Although partial roles of some of these magnetosome proteins have been determined, the roles of most have not been completely elucidated, particularly in how they regulate the biomineralization process. While studies on the localization of these proteins have been focused solely on Magnetospirillum species, the goal of the present study was to determine, for the first time, the localization of the most abundant putative magnetosome membrane protein, MamC, in Magnetococcus marinus strain MC-1. MamC was expressed in Escherichia coli and purified. Monoclonal antibodies were produced against MamC and immunogold labeling TEM was used to localize MamC in thin sections of cells of M. marinus. Results show that MamC is located only in the magnetosome membrane of Mc. marinus. Based on our findings and the abundance of this protein, it seems likely that it is important in magnetosome biomineralization and might be used in controlling the characteristics of synthetic nanomagnetite.
KeywordsMagnetosome Magnetotactic bacteria MamC Magnetococus marinus
This work was supported by Grant CGL2007-63859 and CGL2010-18274 from the Ministerio de Educación, Cultura y Deporte (Spain). B.H.L. and S.K.L. thank Grants EAR-0920299, EAR-0525297, EAR-0745808 from the U.S. National Science Foundation (NSF). D.A.B. is supported by U.S. NSF Grant EAR-0920718 and by SC-12-384 (U.S. DOE C02-07CH11358, Ames Laboratory at Iowa State University). We thank “La Factoría de Cristalización” (Granada) and LEC personnel (IACT, CSIC-UGR) for their assistance in protein expression and purification and also the CIC personnel from the University of Granada for TEM analyses and sample preparation. E.P.M. is supported by “Ramón y Cajal” research contract (MICINN). We thank an anonymous reviewer for their comments that have greatly improved this paper.
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