Ras and rap1 GTPases Mutated at Position 64

Abstract

Ras and Rap1 GTPases require Gly12, the effector domain (residues 32 to 40) and Ala 59 for activation by GAP1 and GAP3, respectively. The replacement of Gly12 by Val or Ala59 by Thr potentiates the Ras oncogenicity and Rap anti-oncogenicity. However, the mutations in the effector domain, in particular the replacement of Thr35 by Ala, abolishes both Ras oncogenicity and Rap anti-oncogenicity, indicating that the effector domains are involved in the interactions of these signal transducers with their targets as well as the GAPs. Here, we demonstrate that replacement of Tyr64 of the HaRas protein or Phe64 of Rap1A protein by Glu reduces their intrinsic GTPase activities and abolishes their stimulation by GAP1 or GAP3, respectively. Further mutational analysis has revealed that only the Tyr to Phe or Leu (Ras) and Phe to Tyr (Rap1A) substitutions at position 64 still allow these GTPases to be activated by GAPs.