title: Alternative splicing of Rac1 generates Rac1b, a self-activating GTPase.
abstract: Rac1b was recently identified in malignant colorectal tumors as an alternative splice variant of Rac1 containing a 19-amino acid insertion next to the switch II region. The structures of Rac1b in the GDP- and the GppNHp-bound forms, determined at a resolution of 1.75 A, reveal that the insertion induces an open switch I conformation and a highly mobile switch II. As a consequence, Rac1b has an accelerated GEF-independent GDP/GTP exchange and an impaired GTP hydrolysis, which is restored partially by GTPase-activating proteins. Interestingly, Rac1b is able to bind the GTPase-binding domain of PAK but not full-length PAK in a GTP-dependent manner, suggesting that the insertion does not completely abolish effector interaction. The presented study provides insights into the structural and biochemical mechanism of a self-activating GTPase.
authors: Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany.
authors: Dennis
authors: D
authors: Fiegen
authors: Lars-Christian
authors: LC
authors: Haeusler
authors: Lars
authors: L
authors: Blumenstein
authors: Ulrike
authors: U
authors: Herbrand
authors: Radovan
authors: R
authors: Dvorsky
authors: Ingrid R
authors: IR
authors: Vetter
authors: Mohammad R
authors: MR
authors: Ahmadian
mesh_terms: D017398:Alternative Splicing; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004268:DNA-Binding Proteins; D004789:Enzyme Activation; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D007700:Kinetics; D008958:Models, Molecular; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; C480633:SLC2A4RG protein, human; D014157:Transcription Factors; D006160:Guanosine Triphosphate; D020830:rac1 GTP-Binding Protein