Magnetite-Binding Flagellar Filaments Displaying the MamI Loop Motif

This work aims at developing a novel method for fabricating 1D magnetite nanostructures with the help of mutagenized flagellar filaments. We constructed four different flagellin mutants displaying magnetite-binding motifs. Two of the mutants contained fragments of magnetosome-associated proteins from magnetotactic bacteria (MamI and Mms6), whereas for the other two mutants synthetic sequences were used. A magnetic selection procedure identified the mutant incorporating the loop segment from MamI to have the highest binding affinity towards magnetite. Filaments built from MamI loop-containing flagellin subunits were used as templates to form chains of magnetite nanoparticles along the filament by capturing them from suspension. Our study presents a proof of concept that flagellar filaments can be engineered to facilitite formation of 1D magnetite nanostructures under ambient conditions. In addition, it proves the interaction between MamI and magnetite, with implications for the role of the protein in magnetotactic bacteria.