Ferrous Iron Binding Key to Mms6 Magnetite Biomineralisation:A Mechanistic Study to Understand Magnetite Formation Using pH Titration and NMR Spectroscopy

Andrea E. Rawlings, Jonathan P. Bramble, Andrea M. Hounslow, Michael P. Williamson, Amy Monnington, David J. Cooke, Sarah S. Staniland

Research output: Contribution to journalArticlepeer-review

Abstract

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 under-stand 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 mineral s,suggesting Mms6 has a hitherto unrecorded ferrous iron in-teracting 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.
Original languageEnglish
Pages (from-to)7885-7894
JournalChemistry - A European Journal
Volume22
Issue number23
Early online date26 Apr 2016
DOIs
Publication statusPublished - 27 May 2016

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