There are more than a hundred proteins in the Ras superfamily. Based on structure, sequence and function, the Ras superfamily is divided into five main families (Ras, Rho, Ran, Rab and Arf GTPases). The Ras family itself is further divided into 6 subfamilies: Ras, Ral, Rit, Rap, Rheb, Rad and Rit. Miro is a recent contributor to the superfamily. Each subfamily shares the common core G domain, which provides essential GTPase and nucleotide exchange activity.
The surrounding sequence helps determine the functional specificity of the small GTPase, for example the 'Insert Loop', common to the Rho subfamily, specifically contributes to binding to effector proteins such as WASP.
In general, the Ras family is responsible for cell proliferation: Rho for cell morphology, Ran for nuclear transport, and Rab and Arf for vesicle transport.