Low Energy Conformations for S100 Binding Peptide from the Negative Regulatory Domain of p53.

We have computed the low energy conformations of the negative regulatory domain of p53, residues 374-388 using Empirical Conformational Energies of Peptides Program including solvation and computed the statistical weights of distinct conformational states. We find that there are two high probability conformations, one an α-helix from Lys 374-Lys 381, followed by another helical structure involving Lys 382-Glu 388 (statistical weight of 0.48) and an all-α-helix for the entire sequence (statistical weight of 0.23). Both structure are superimposable on the NMR structure of this sequence bound to the S100 protein. The global minimum structure (statistical weight of 0.014) is a beta structure from Gly 374-Arg 379 followed by an α-helix from His 380-Glu 388. Based on these results, we propose a possible strategy for enhancement of p53 anti-tumor activity in cancer cells. Since the structure of this sequence bound to the sirtuin protein, Sir2, is a β-sheet, we further propose that the global minimum may be an intermediate on the α-β structure transition.