Termini of Salmonella flagellin are disordered and become organized upon polymerization into flagellar filament

The terminal regions of Salmonella flagellin are essential for polymerization to form the flagellar filament. It has recently been suggested, on the basis of results from circular dichroism spectroscopy and scanning calorimetry, that these regions are disordered in solution. We report here direct evidence for disorder and mobility in the terminal regions of flagellin using 400 MHz proton nuclear magnetic resonance (n.m.r.) spectroscopy. Comparison of the n.m.r. spectra of monomeric and polymeric flagellin shows that the terminal regions become organized when polymerized to form the filament.