STRUCTURE OF THE FIBER-FORMING PROTEIN PILIN AT 2.6-ANGSTROM RESOLUTION

The crystallographic structure of Neisseria gonorrhoeae pilin, which a ssembles into the multifunctional pilus adhesion and virulence factor, reveals an alpha-beta roll fold with a striking 85 Angstrom alpha-hel ical spine and an O-linked disaccharide. Hey residues stabilize intera ctions that allow sequence hypervariability, responsible for pilin's c elebrated antigenic variation, within disulphide region beta-strands a nd connections. Pilin surface shape, hydrophobicity and sequence varia tion constrain pilus assembly to the packing of flat subunit faces aga inst alpha(1) helices. Helical fibre assembly is postulated to form a core of coiled alpha(1) helices banded by beta-sheet, leaving carbohyd rate and hypervariable sequence regions exposed to solvent.