title: The Rac-RhoGDI complex and the structural basis for the regulation of Rho proteins by RhoGDI.
abstract: Rho family-specific guanine nucleotide dissociation inhibitors (RhoGDIs) decrease the rate of nucleotide dissociation and release Rho proteins such as RhoA, Rac and Cdc42 from membranes, forming tight complexes that shuttle between cytosol and membrane compartments. We have solved the crystal structure of a complex between the RhoGDI homolog LyGDI and GDP-bound Rac2, which are abundant in leukocytes, representing the cytosolic, resting pool of Rho species to be activated by extracellular signals. The N-terminal domain of LyGDI (LyN), which has been reported to be flexible in isolated RhoGDIs, becomes ordered upon complex formation and contributes more than 60% to the interface area. The structure is consistent with the C-terminus of Rac2 binding to a hydrophobic cavity previously proposed as isoprenyl binding site. An inner segment of LyN forms a helical hairpin that contacts mainly the switch regions of Rac2. The architecture of the complex interface suggests a mechanism for the inhibition of guanine nucleotide dissociation that is based on the stabilization of the magnesium (Mg2+) ion in the nucleotide binding pocket.
authors.affiliation: Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Str. 11, 44227 Dortmund, Germany. klaus@mpimf-heidelberg.mpg.de
authors.forename: K
authors.initials: K
authors.lastname: Scheffzek
authors.forename: I
authors.initials: I
authors.lastname: Stephan
authors.forename: O N
authors.initials: ON
authors.lastname: Jensen
authors.forename: D
authors.initials: D
authors.lastname: Illenberger
authors.forename: P
authors.initials: P
authors.lastname: Gierschik
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D018360:Crystallography, X-Ray; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000737:chemistry* / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000737:chemistry / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D050356:Lipid Metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D000097766:RAC2 GTP-Binding Protein
chemical_list: D020730:Guanine Nucleotide Dissociation Inhibitors; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D011506:Proteins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D000097766:RAC2 GTP-Binding Protein; C086796:GDP dissociation inhibitor 1