TP53 and cancer: 1. Chemo- and regioselectivity: In theunmodified protein, cysteine residues C182/C229/C275/C277 are solventexposed and freely accessible, while C124/135/141/176/238/242 aresterically hindered and/or involved in structural Zn(II) coordination.The cancer specific C220 lies at the bottom of a mutationally inducedhydrophobic pocket at the surface of the p53 DNA-binding domain (DBD,25 kDa) and is also sterically hindered.