Ric1 is part of the RIC1-RGP1 complex that acts as a guanine nucleotide exchange factor (GEF) for Rab6 GTPase, which is important for normal Golgi structure and function [, ].
This entry represents RIC1 (Ribosomal control protein1) and has been identified in yeast as a Golgi protein involved in retrograde transport to the cis-Golgi network. It forms a heterodimer with Rgp1 and functions as a guanyl-nucleotide exchange factor []which activates YPT6 by exchanging bound GDP for free GTP. RIC1 is thereby required for efficient fusion of endosome-derived vesicles with the Golgi. The RIC1-RGP1 complex participates in the recycling of SNC1, presumably by mediating fusion of endosomal vesicles with the Golgi compartment and may also be indirectly involved in the transcription of both ribosomal protein genes and ribosomal RNA [, , ].
This entry represents a group of plant CRIB domain-containing proteins including RIC1-11 (exclude 2 and 4) from Arabidopsis. They belong to the RIC (ROP-interactive CRIB motif-containing protein) family. RIC1 is inactivated by active ROP2 in the lobe-forming regions of pavement cells, which suppresses MT assembly, but promotes fine F-actin assembly and thereby induces outgrowth of the region. In contrast, RIC1 is activated by active ROP6 in the neck-forming regions of pavement cells, and then promotes the assembly of MTs, which limits the expansion of the region and results in the formation of a narrow neck. RIC1 also positively regulates the auxin effect and negatively regulates the ABA effect during root growth and lateral root development [].RIC7 functions as downstream effector of active ROP2 which is involved in the prevention of excessive stomatal opening upon light stimulation []. It is also involved in pollen tube growth regulation through its interaction with ROP1 [].The RIC (ROP-interactive CRIB motif-containing protein) family members act as Rho GTPase (Rop) targets that function in distinct Rop signaling pathways []. RICs interact with multiple ROP GTPases via their conserved CRIB motif, and link ROP proteins to diverse target molecules that bind to their variable domains []. RICs share several consensus amino acid residues upstream of the CRIB motif and a consensus PSWMXDFK block downstream of the CRIB motif. Unlike other group members, members of group V, consisting of RIC4 and RIC2, lack the PSWMXDFK block and contain a relatively long N terminus in front of the CRIB motif and a short C terminus [].
