Structure of the Neisseria meningitidis Type IV pilus

Neisseria meningitidis use Type IV pili (T4P) to adhere to endothelial cells and breach the blood brain barrier, causing cause fatal meningitis. T4P are multifunctional polymers of the major pilin protein, which share a conserved hydrophobic N terminus that is a curved extended alpha-helix, alpha 1, in X-ray crystal structures. Here we report a 1.44 angstrom crystal structure of the N. meningitidis major pilin PilE and a similar to 6 angstrom cryo-electron microscopy reconstruction of the intact pilus, from which we built an atomic model for the filament. This structure reveals the molecular arrangement of the N-terminal alpha-helices in the filament core, including a melted central portion of alpha 1 and a bridge of electron density consistent with a predicted salt bridge necessary for pilus assembly. This structure has important implications for understanding pilus biology.