[Mechanism of flagellin polymerization in Bacillus brevis]

The optical properties of acid-dissociated and tetranitromethane-modified flagellin has been studied by circular dichroism (CD) techniques. The flagellins have the same CD spectra which do not change over the 2.9-10.0 range. The spectra character depends on pH in the presence of polyethylene glycol (PEG) and ammonium sulphate which accelerate polymerization. As the content of PEG goes up to 20% and ammonium sulphate to 1 M, the value of the molecular ellipticity at 222 nm ([O]222) of the both flagellins considerably increases at pH 4.3-10.0, however [O]222 does not achieve the value for bacterial flagella. PEG and ammonium sulphate addition at pH 2.9-3.9 gives less dramatic increase of the [O]222 value. It has been concluded that the changes in the CD spectra at pH 4.3-10.0 is a result of conformational rearrangements in flagellin before it incorporates into the flagella.