FIG. 5.

Identification of arginines essential for TSC2 GAP activity. (A) The GTP-to-GDP ratio of Rheb was measured in the presence of wild-type and mutant TSC2 as indicated. The expression levels of TSC1 and TSC2 (middle) and quantification of GAP activity of TSC2 point mutations (bottom) are shown. (B) Inhibition of S6K by TSC2 arginine mutants. HA-S6K and wild-type (WT) or mutant TSC2 were cotransfected into HEK293 as indicated. Phosphorylation of S6K was determined by phosphospecific antibody against phospho-pS6K(T389). (C) Inhibition of S6K by the TSC2 wild type and mutants. Experiments were similar to those described above (B).