PTEN missense mutation that results in the substitution of arginine at position 130 with glycine affects the conserved H-C-K/R-A-G-K-G-R sequence (corresponding to HCXXGXXR motif of protein tyrosine phosphatases) in the catalytic cleft of the PTEN phosphatase domain. The arginine residue in this motif, corresponding to R130 of human PTEN, is essential for catalysis (Barford et al. 1994, Lee et al. 1999). PTEN R130G (Arg130Gly) mutant shows markedly decreased phosphoinositide phosphatase activity (Han et al. 2000, Koul et al. 2002). PTEN R130G substitution is frequently found in endometrial carcinoma (Kong et al. 1997, Konopka et al. 2007).