Type three secretion systems consist of a multisubunit protein complex that crosses the bacterial membranes and an extracellular needle-shaped structure. New data show that the needle protomer partially refolds from alpha-helix into beta-strand conformation to extend the needle from the distal end. The closely related flagellar system also grows at the tip, but it is not known whether protomer refolding is required for its assembly.
- Ömer Poyraz
- Holger Schmidt
- Michael Kolbe
