ANALYSIS OF THE CONFORMATION AND STABILITY OF RAT TTF-1 HOMEODOMAIN BY CIRCULAR-DICHROISM

The conformational stability of TTF-1HD has been determined by CD-moni tored thermal denaturation and isothermal urea unfolding studies. The Gibbs free energy of stabilization found are 1.44 and 1.26 kcal.mol(-1 ), respectively. TTF-1HD exhibits a T-m of 42 degrees C and a Delta C- p of 80 cal.mol(-1) K-1 indicating that TTF-1HD, when free in solution , is a mobile flexible segment folded into loose helices. Such a flexi bility would be relevant for the DNA-binding function of this homeodom ain. In fact, a small reduction of the alpha-helical content of TTF-1H D significally modifies its DNA-binding activity.