The binding of maltose to 'virgin' maltose-binding protein is biphasic

The biphasic binding properties of the galactose-binding and maltose-binding proteins of Escherichia coli may be important in the functioning of these proteins as recognition components of chemoreceptors. However, Richarme and Kepes [Eur. J. Binding curve of the galactose-binding protein may be the result of isotopic dilution, during equilibrium dialysis, by unlabeled ligand retained by the binding throughout purification. Here the binding of maltose to maltose-binding protein which has never previously been exposed to sugar ('virgin' binding protein) is shown to be biphasic. This implies that the unusual binding properties are attributable to the maltose-binding protein itself.