A preliminary structural analysis of Vibrio cholerae zonula occludens toxin (ZOT) was made by equilibrium denaturation and circular dichroism. ZOT is a structurally unstable protein in aqueous solution (DeltaG((H2O)) 3.82 kcal/mol), the putative intra- and extracellular domains unfold co-operatively, with complete denaturation via observed conformational intermediates. Refolding of denatured ZOT is not dependent on disulphide bridge formation. Partial refolding of a maltose binding protein-ZOT fusion did not prevent its specific binding to the ZOT receptor on Caco-2 cells. Immuno-gold labelling showed that the ZOT receptor localises to the intercellular contacts between cells in a confluent monolayer.
Lee, A., White, N., & van der Walle, C. F. (2003). The intestinal zonula occludens toxin (ZOT) receptor recognises non-native ZOT conformers and localises to the intercellular contacts. FEBS Letters, 555(3), 638-642. https://doi.org/10.1016/s0014-5793(03)01348-6