Figure 1: Protein domain structures of PIK3CA and AKT1 with hotspot mutations. A) PIK3CA. The most common mutations in each domain are listed. The heights of the vertical bars indicate relative frequency of mutation in each domain. ABD: adapter binding domain (p85 subunit); RBD: Ras binding domain. B) AKT1. While all reported breast cancer mutations are E17K (100%), the overall frequency of AKT1 mutations in breast cancer is 1/10-1/5 that of PIK3CA mutations, as illustrated by the relative height of the bar. The C-terminal regulatory tail contains a hydrophobic motif [37].