A THERMODYNAMIC STUDY OF THE BINDING OF LINEAR AND CYCLIC OLIGOSACCHARIDES TO THE MALTODEXTRIN-BINDING PROTEIN OF ESCHERICHIA-COLI

Isothermal titration calorimetric (ITC) studies over a range of temper atures of the binding of maltose, maltotriose, maltotetraose and beta- cyclodextrin to the maltodextrin-binding protein (MBP) of Escherichia coil are reported. The binding constants of maltose, maltotriose and b eta-cyclodextrin are not very different, namely 8.7 x 10(5), 13.0 x 10 (5) and 2.55 x 10(5) M-1, respectively at 25 degrees C. The calorimetr ic data obtained with maltotetraose cannot be interpreted in terms of a definite binding constant. The binding of maltose and maltotriose is endothermic with a large entropy increase while that of beta-cyclodex trin is exothermic, with a smaller entropy increase. The binding of ma ltotetraose was endothermic or exothermic depending on the temperature . (C) 1998 Elsevier Science B.V.