Figure 1. . Schematic representation of Rap1 activation by GEFs.

Rap switches from an inactive form, bound to GDP, to an active conformation, bound to GTP. GEFs, such as C3G or Epac, mediate GDP dissociation, favoring GTP binding to Rap. To inactivate it, GAPs activate Rap intrinsic GTPase activity, promoting GTP hydrolysis.