Ferrous Iron Binding Key to Mms6 Magnetite Biomineralisation: A Mechanistic Study to Understand Magnetite Formation Using pH Titration and NMR Spectroscopy.
Formation of magnetite nanocrystals by magnetotactic bacteria is controlled by specific proteins which regulate the particles' nucleation and growth. One such protein is Mms6. This small, amphiphilic protein can self-assemble and bind ferric ions to aid in magnetite formation. To understand the role of Mms6 during in vitro iron oxide precipitation we have performed in situ pH titrations. We find Mms6 has little effect during ferric salt precipitation, but exerts greatest influence during the incorporation of ferrous ions and conversion of this salt to mixed-valence iron minerals, suggesting Mms6 has a hitherto unrecorded ferrous iron interacting property which promotes the formation of magnetite in ferrous-rich solutions. We show ferrous binding to the DEEVE motif within the C-terminal region of Mms6 by NMR spectroscopy, and model these binding events using molecular simulations. We conclude that Mms6 functions as a magnetite nucleating protein under conditions where ferrous ions predominate.
Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK.
Andrea E
0000-0003-3465-4195
AE
Rawlings
Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK.
Jonathan P
JP
Bramble
Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
Andrea M
AM
Hounslow
Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, UK.
Michael P
0000-0001-5572-1903
MP
Williamson
Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
Amy E
AE
Monnington
Department of Chemical and Biological Sciences, University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, UK.
David J
DJ
Cooke
Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK. s.s.staniland@sheffield.ac.uk.
Sarah S
0000-0001-8995-7172
SS
Staniland
NMR spectroscopy; biomimetic synthesis; magnetite; magnetotactic bacteria; mineralization