The arginine residue at position 38 of PIK3CA (R38) is located at a contact site between the ABD and kinase domains of PIK3CA. Substitution of this arginine residue with serine in PIK3CA R38S mutant is likely to disrupt the interaction between the ABD domain and the kinase domain, causing a confomrational change of the kinase domain that leads to increased enzymatic activity (Huang et al. 2007).
Huang, CH, Mandelker, D, Schmidt-Kittler, O, Samuels, Y, Velculescu, VE, Kinzler, KW, Vogelstein, B, Gabelli, SB, Amzel, LM
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