The Binding of Maltose to ‘Virgin’ Maltose‐Binding Protein is Biphasic

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Abstract
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. Biochem. 45, 127‐133 (1974)] have suggested that the biphasic 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 the sugar (‘virgin’ binding protein) is shown to be biphasic. This implies that the unusual binding properties are attributable to the maltose‐binding protein itself.