N. Morii et al., RHO GAP OF 28 KDA (GAP2), BUT NOT OF 190 KDA (P190), REQUIRES ASP(65)AND ASP(67) OF RHO GTPASE FOR ITS ACTIVATION, The Journal of biological chemistry, 268(36), 1993, pp. 27160-27163
Two distinct GTPase-activating proteins (GAPs), i.e. rho GAPs of 28 kD
a (GAP2) and of 190 kDa (p190), stimulate the intrinsic GTPase activit
y of the rho protein. The rho GAP activity of p190 resides in its C-te
rminal domain (p190C). Neither GAP2 nor p190C activates the ras GTPase
. We replaced Asp65 and Asp67 residues of rho GTPase with the correspo
nding ras residues and examined whether the domain containing them is
involved in its activation by rho GAPs. Mutation of either Asp65 to Gl
u or Asp67 to Ser did not change the K(d) value for GTPgammaS of the r
ho protein. The Ser67 mutation reduced the intrinsic GTPase activity o
f the rho protein, while no change was observed with the Glu65 mutatio
n. Both mutations abolished activation of rho GTPase by GAP2. The GAP2
-dependent activation of rho GTPase was inhibited by the addition of G
TPgammaS-bound wild type rho but not by either GTPgammaS-bound Glu65-
or Ser67-rho, indicating that both Asp65 and Asp67 are essential for i
nteraction of rho protein with GAP2. On the contrary, p190C activated
both Glu65- and Ser67-rho GTPases to the extent and in a dose dependen
ce to those seen in the wild GTPase. These results suggest that GAP2 a
nd p190 interact with different residues or domains of the rho GTPase
for their activation.