DNA-binding protein nanotubes: Learning from nature's nanotech examples

Bacterial pili are nanofibers made of protein subunits. Here we report the controlled assembly of protein nanotubes from an engineered Pseudomonas aeruginosa type IV pilin monomer. The nanotubes are up to 100 mum long with an outer diameter of similar to6 nm and a predicted inner diameter of similar to2 nm. Protein nanotube formation appears to proceed through a hydrophobe-initiated conformational shift in the pilin monomer, which then self-associates to form thin linear filaments that coalesce to form long protein nanotubes. Protein nanotubes are highly attractive for nanotechnology, as protein engineering confers unprecedented control over mechanical and chemical properties. Moreover, like type IV pili, our nanotubes bind DNA, further broadening their appeal in nanotechnological applications.