Question

What are the similarities and differences between the reactions that lead to the activation of G proteins and the reactions that leads to the activation of Ras?

Answer 1

Both are transmembrane proteins. Both GPCR and Ras have an active GTP bound form and an inactive GDP bound form.

One major difference between the systems is that the intrinsic GTPase activity of Ras is far lower than that of heterotrimeric G protein α subunits. ... Upon binding GTP, there is a major conformational change in Ras, which is thought to be responsible for its functional activation.