Rop (Rho of plants), are small plant specific GTP-binding proteins, which acts as switches in signalling processes. Activation, as with other GTP binding proteins, depends on guanine nucleotide exchange factors (GEFs) which catalyse GDP dissociation for subsequent GTP binding. According to the available literature, structural domains which comprise this superfamily correspond to the structure of a component of PRONE, which stands for Plant-specific Rop nucleotide exchanger and is a highly conserved catalytic domain of RopGEFs. PRONE has been shown to be both necessary and sufficient to promote nucleotide release from Rop PMID:19335195 PMID:15980860.

This domain is however divided in two subdomains, named respectively subdomain 1 and subdomain 2 PMID:17218277 the structure of members of this superfamily corresponds to that of subdomain 2. The function of each subdomain has yet to be determined.