Modulation of a GEF switch: autoinhibition of the intrinsic guanine nucleotide exchange activity of p115-RhoGEF.
p115-RhoGEF (p115) belongs to the family of RGS-containing guanine nucleotide exchange factors for Rho GTPases (RGS-RhoGEFs) that are activated by G12 class heterotrimeric G protein α subunits. All RGS-RhoGEFs possess tandemly linked Dbl-homology (DH) and plekstrin-homology (PH) domains, which bind and catalyze the exchange of GDP for GTP on RhoA. We have identified that the linker region connecting the N-terminal RGS-homology (RH) domain and the DH domain inhibits the intrinsic guanine nucleotide exchange (GEF) activity of p115, and determined the crystal structures of the DH/PH domains in the presence or absence of the inhibitory linker region. An N-terminal extension of the canonical DH domain (the GEF switch), which is critical to GEF activity, is well folded in the crystal structure of DH/PH alone, but becomes disordered in the presence of the linker region. The linker region is completely disordered in the crystal structure and partially disordered in the molecular envelope calculated from measurements of small angle x-ray scattering (SAXS). It is possible that Gα subunits activate p115 in part by relieving autoinhibition imposed by the linker region.
Department of Pharmacology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA. Zhe.Chen@utsouthwestern.edu
Zhe
Z
Chen
Liang
L
Guo
Stephen R
SR
Sprang
Paul C
PC
Sternweis
D020816:Amino Acid Motifs; D018360:Crystallography, X-Ray; D020662:Guanine Nucleotide Exchange Factors / Q000037:antagonists & inhibitors / Q000737:chemistry*; D006801:Humans; D017434:Protein Structure, Tertiary; D064067:Rho Guanine Nucleotide Exchange Factors; D053838:Scattering, Small Angle; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
C576600:ARHGEF1 protein, human; D020662:Guanine Nucleotide Exchange Factors; D064067:Rho Guanine Nucleotide Exchange Factors