Reduced pH causes structural changes in the potent mitogenic toxin of Pasteurella multocida

Pasteurella multocida toxin is a potent mitogen that is believed to act int racellularly, On transverse urea gradient gels at pH 8.0 the toxin displaye d one major unfolding transition at 4 M urea, However, at pH 6.1 the unfold ing transition took place at 3.5 M urea. Circular dichroism spectra also in dicated that a structural change took, place at acidic pH. In addition it w as found that the toxin that had been denatured in 8 M urea refolded in sol ution with a high recovery of biological activity. These findings are discu ssed in terms of the likely domain structure of the P. multocida toxin. (C) 1999 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.