Localization of Native Mms13 to the Magnetosome Chain of Magnetospirillum magneticum AMB-1 Using Immunogold Electron Microscopy, Immunofluorescence Microscopy and Biochemical Analysis

Magnetotactic bacteria (MTB) biomineralize intracellular magnetite (Fe3O4) crystals surrounded by a magnetosome membrane (MM). The MM contains membrane-specific proteins that control Fe3O4 mineralization in MTB. Previous studies have demonstrated Mms13 is critical protein within the MM. can be isolated from fraction of Magnetospirillum magneticum AMB-1 and homolog, MamC, has been shown to size shape nanocrystals synthesized in-vitro. objective this study was use several independent methods definitively determine localization native M. AMB-1. Using Mms13-immunogold labeling transmission electron microscopy (TEM), we found localized chain cells. detected direct contact with or Immunofluorescence detection cells confocal laser scanning (CLSM) showed along length chain. Proteins contained were resolved SDS-PAGE for Western blot analysis LC-MS/MS (liquid chromatography tandem mass spectrometry) sequencing. Anti-Mms13 antibody, band molecular ~14 kDa only. This polypeptide digested trypsin, sequenced identified as Mms13. Peptides corresponding protein’s putative domain catalytic both LC-MS/MS. Our results (Immunogold TEM, CLSM, blot, LC-MS/MS), combined previous studies, demonstrate homolog MamC Mam12, are MTB belonging class Alphaproteobacteria. Because their shared highly conserved amino acid sequences, it likely share similar roles biomineralization nanocrystals.