A new family of RhoGEFs activates the Rop molecular switch in plants.
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. Although numerous RhoGEFs exist in animals and yeasts, no Rop-specific GEFs have yet been identified in plants and so Rop activation has remained elusive. Here we describe a new family of RhoGEF proteins that are exclusive to plants. We define a unique domain within these RopGEFs, termed PRONE (plant-specific Rop nucleotide exchanger), which is exclusively active towards members of the Rop subfamily. It increases nucleotide dissociation from Rop more than a thousand-fold and forms a tight complex with nucleotide-free Rop. RopGEFs may represent the missing link in signal transduction from receptor kinases to Rops and their identification has implications for the evolution of the Rho molecular switch.
Berken
Antje
A
Max Planck Institute of Molecular Physiology, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany. antje.berken@mpi-dortmund.mpg.de
Thomas
Christoph
C
Wittinghofer
Alfred
A
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000145:classification* / Q000235:genetics / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D005810:Multigene Family; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D064067:Rho Guanine Nucleotide Exchange Factors; D013379:Substrate Specificity; D020798:Two-Hybrid System Techniques
D029681:Arabidopsis Proteins; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases