Structural domains comprising this superfamily share the structure of two shown to be homologous GTPase activating proteins for Rap and Ran. Both are Ras-like guanine-nucleotide-binding proteins (GNBPs) involved in a variety of signal-transduction processes and their activity is regulated by GEFs and GAPs. Rap has been implicated in various cellular processes such as exocytosis, cAMP signalling, cell adhesion and cell proliferation PMID:11331911. Ran, also known as GTP-binding nuclear protein, is on the other hand essential for the translocation of RNA and proteins through the nuclear pore complex and has been implicated in the control of DNA synthesis and cell cycle progression.

Both Rap and Ran proteins acts as molecular switches, with an active GTP-bound form and an inactive GDP-bound form, with GAPs promoting GTP binding and thus activating them. Like any other GAPs, they increase the slow intrinsic GTPase reaction for small GTP Ras-like GNBPs by many orders of magnitude and allow tight regulation of signalling PMID:15141215.