Structure-function studies of the magnetite-biomineralizing magnetosome-associated protein MamC

J Struct Biol. 2016 Jun;194(3):244-52. doi: 10.1016/j.jsb.2016.03.001. Epub 2016 Mar 10.

Abstract

Magnetotactic bacteria are Gram-negative bacteria that navigate along geomagnetic fields using the magnetosome, an organelle that consists of a membrane-enveloped magnetic nanoparticle. Magnetite formation and its properties are controlled by a specific set of proteins. MamC is a small magnetosome-membrane protein that is known to be active in iron biomineralization but its mechanism has yet to be clarified. Here, we studied the relationship between the MamC magnetite-interaction loop (MIL) structure and its magnetite interaction using an inert biomineralization protein-MamC chimera. Our determined structure shows an alpha-helical fold for MamC-MIL with highly charged surfaces. Additionally, the MamC-MIL induces the formation of larger magnetite crystals compared to protein-free and inert biomineralization protein control experiments. We suggest that the connection between the MamC-MIL structure and the protein's charged surfaces is crucial for magnetite binding and thus for the size control of the magnetite nanoparticles.

Keywords: Biomineralization; Magnetotactic bacteria; MamC; Protein structure; Structure–activity relationships.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Ferrosoferric Oxide* / metabolism
  • Gram-Negative Bacteria / chemistry*
  • Gram-Negative Bacteria / metabolism
  • Magnetosomes / chemistry*
  • Magnetosomes / physiology
  • Magnetospirillum
  • Nanoparticles / chemistry
  • Protein Binding
  • Structure-Activity Relationship

Substances

  • Bacterial Proteins
  • Ferrosoferric Oxide