Terminal disorder: a common structural feature of the axial proteins of bacterial flagellum?

We report, based on proteolytic experiments and high resolution 1H nuclear magnetic resonance studies that the terminal regions of the monomeric hook protein are highly mobile and exposed to the solvent. The disordered parts of the hook protein span approximately the first 70 and the last 30 amino acid residues. Although the amino acid sequences of flagellin and hook protein do not resemble each other at all, both proteins have now been shown to contain large disordered terminal regions. Sequential similarities of flagellin and hook protein, especially near the NH2 and COOH termini, to other axial components of bacterial flagellum suggest that terminal disorder may be a common structural feature of the axial proteins of the bacterial flagellum.