Question

how would a GTPase activating protein inhibit Ras?

Answer 1

Ras, Rab, Ran, Arf and Rho are belongs to the small G proteins family. Similar to the heterotrimeric G-proteins they also rotate between an inactive GDP-bound (guanosine diphosphate) and active GTP-bound form. But, these small G proteins occur as monomers and they are smaller in size than the heterotrimers.

The GTPase activating proteins activate the GTPase activity of G proteins and causes the GTP hydrolysis, which leads to Ras inactivation.

If any mutation results in decreased rate of GTP hydrolysis by RAS or decreases the RAS affinity towards GDP, this causes RAS to be active for more time, allowing more downstream signal that leads to cell proliferation.?