Protein nanotubes (PNTs) have emerged as a novel tool in drug delivery due to their large central cavity and increased biocompatibility compared to other nanosystems, such as carbon nanotubes. Additionally, PNTs can be assembled under physiological conditions and can be readily modified to a particular environment. In this work we focus on PNTs assembled from chemically modified type IV pilin subunits from the bacterial organism Pseudomonas aeruginosa. Type IV pilins make up protein filaments that are used by bacteria for a variety of important functions, however experiments have demonstrated that the pilin from P. aeruginosa strain K122-4 is also able to form PNTs under specific conditions when its N-terminal domain is truncated. The proposed mechanism of pilin PNT assembly involves the formation of oligomers of these truncated pilin subunits, starting with the formation of a pilin dimer. Using the Amber molecular dynamics software, we investigate the dynamics of pilin monomers and dimers from P. aeruginosa to probe the stability of small pilin assemblies. While there has been previous simulation work on type IV pilus (T4P) filaments, there has been less simulation work done on pilin monomers, dimers and other small aggregates. We carry out simulations of pilin monomers and dimers for both the K122-4 and the PAK strains of P. aeruginosa. We also model small PNTs composed of 6, 8, 10, and 18 truncated pilin monomers under different temperature and salt conditions to investigate the stability of PNTs. Initial simulations suggest that the model of a pilin PNT as a T4P filament with a truncated pilin N-terminal helix might not alone be sufficient to describe the experimentally observed stability of modified P. aeruginosa nanotube structures.

Investigating the stability of protein nanotubes composed of P. aeruginosa type IV pilins using molecular dynamics simulations

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.