p53 is a key regulator of the cell cycle and apoptosis which is essential for maintenance of genome integrity (1–4). It can function as a transcription factor, but other roles in DNA repair, homologous recombination and the regulation of its own mRNA translation have been proposed. p53 has also been reported to display intrinsic proteolytic activity (5,6). Importantly, p53 can adopt different tertiary structures. These can be monitored with a panel of monoclonal antibodies that react with the various conformations associated with different functions of the protein (7,8).