InterPro domain: IPR005512

In plants, the small GTP-binding proteins called Rops work as signalling switches that control growth, development and plant responses to various environmental stimuli. Rop proteins (Rho of plants, Rac-like and atRac in Arabidopsis thaliana belong to the Rho family of Ras-related GTP-binding proteins that turn on signalling pathways by switching from a GDP-bound inactive to a GTP-bound active conformation. Activation depends on guanine nucleotide exchange factors (GEFs) that catalyse the otherwise slow GDP dissociation for subsequent GTP binding. The plant-specific RopGEFs represent a unique family of exchange factor that display no homology to any known RhoGEFs from animals and fungi. They comprise a highly conserved catalytic domain termed PRONE (plant-specific Rop nucleotide exchanger) with exclusive substrate specificity for members of the Rop family. The PRONE domain has been shown to be necessary and sufficient to promote nucleotide release from Rop [ 1 , 2 , 3 ].

The PRONE domain can be divided into three highly conserved subdomains separated by two short stretches of variable amino acid residues [ 4 , 4 ]. It is approximately 370 residues in length and displays an almost all alpha-helical structure except for a beta-turn that protrudes from the main body of the molecule. The overall structure of the PRONE domain can be divided into two subdomains, the first one including helices alpha1-5 and alpha13, the second alpha6-12 [ 4 , 5 ].

1. A new family of RhoGEFs activates the Rop molecular switch in plants. Nature 436, 1176-80
2. Members of a novel class of Arabidopsis Rho guanine nucleotide exchange factors control Rho GTPase-dependent polar growth. Plant Cell 18, 366-81
3. Purification and crystallization of the catalytic PRONE domain of RopGEF8 and its complex with Rop4 from Arabidopsis thaliana. Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun. 62, 607-10
4. Structural evidence for a common intermediate in small G protein-GEF reactions. Mol. Cell 25, 141-9