Book of Abstracts: Albany 2007
June 19-23 2007
p53 Tumour Suppressor: Structure, Function-Rescue
Systematic mutagenesis has been one of the most powerful tools for elucidating the principles of protein folding and stability. Mutation is the principle cause of cancer, and the technology for studying simple folding can be transferred to the study of proteins involved in cancer. Some 50% of human cancers have mutations that inactivate the tumor suppressor p53. Virtually all of the oncogenic mutations reside in the core domain that binds specifically to DNA. We have found that a significant proportion of the mutations inactivate the protein by lowering its melting temperature to body temperature or below. This has raised the possibility of designing small molecules that rescue those oncogenic mutants simply by binding to the native state of the protein and, hence, raising its melting temperature by the principal of mass action. To understand further the structure of the protein and, hence, the rational design of drugs, we are attempting to solve its structure at high resolution. We are faced with twin problems: the tetrameric protein consists of 1572 residues, some of which are in well-structured domains but others are natively unfolded; and the important core domain is intrinsically unstable and not well suited to systematic study. We have solved the structure of the core domain in solution by state-of-the-art NMR methods and found structural reasons for its instability. We have engineered a more stable variant, which is biologically active and have solved the crystal structures of oncogenic mutants in this framework. Some cancer mutations cause surface cavities that are drug targets. We are now attempting to solve the structure of the full-length tetrameric complex by combining high-resolution structural information on the folded individual domains with NMR and other structural studies on the full-length protein to map out its domain organization.
Cambridge University and MRC Centre for Protein Engineering