Self-assembling protein nanotubes (PNTs) are an intriguing alternative to carbon nanotubes for applications in bionanotechnology, in part due to greater inherent biocompatibility. The type IV pilus of the gram negative bacteria Pseudomonas aeruginosa is a protein-based fibre composed of a single monomeric subunit, the type IV pilin. Engineered pilin monomers from P. aeruginosa strain K122-4 (K122) have been shown to oligomerize into PNTs both in solution and at surfaces. In order to fully exploit PNTs in bionanotechonological settings, an in-depth understanding of their assembly, physical characteristics, robustness etc., both in solution and when constrained to surfaces, is required. Characterization of the oligomerization process in solution suggests that protein is in a monomer-dimer equilibrium in solution, and that PNT oligomerization is a fibril-mediated process. Examination of the structural changes occurring between the monomeric and dimeric states of K122, the N-terminal alpha-helix and the loop connecting the second and third strands of the anti-parallel beta-sheet contribute significantly to pilin dimerization. Conversely, the antiparallel beta-sheet and alpha/beta loop region exhibit increased flexibility, while the receptor binding domain retains a rigid conformation in the equilibrium state. These observations suggest a mechanism of PNT oligomerization, however a fulsome model of this process, both in solution and at surfaces, remains unclear.