THE EFFECTS OF SALT ON THE TATA-BINDING PROTEIN-DNA INTERACTION FROM A HYPERTHERMOPHILIC ARCHAEON

This study investigates the thermodynamics of the interaction of the T ATA box binding protein (TBP) from Pyrococcus woesei (Pw) with an olig onucleotide containing a specific binding site. Pw is a hyperthermophi lic archeal organism which exists under conditions of high salt and hi gh temperature. A measurable protein-DNA interaction only occurs at hi gh salt concentrations. Isothermal titration calorimetric binding stud ies were performed under a range of salts (potassium chloride, potassi um phosphate, potassium acetate and sodium acetate) at varying concent rations (0.8 to 1.6 M). At the high salt concentrations used the obser ved equilibrium binding constant increases with increasing salt concen tration. This is very different to the effect reported for all other p rotein-DNA interactions which have been studied at lower salt concentr ations. Thermodynamic data suggest that the protein-DNA interaction at high salt concentration is accompanied by the removal of large number s of water molecules from the buried hydrophobic surface area. In addi tion, the involvement of ions appears to influence the binding which c an be explained by binding of cations in the interface between the ele ctrostatically negative lateral lobes on the protein and the negativel y charged DNA. (C) 1998 Academic Press Limited.