Activation of leukemia-associated RhoGEF by Gα13 with significant conformational rearrangements in the interface

Nobuchika Suzuki, Kouhei Tsumoto, Nicole Hajicek, Kenji Daigo, Reiko Tokita, Shiro Minami, Tatsuhiko Kodama, Takao Hamakubo, Tohru Kozasa

Research output: Contribution to journalArticlepeer-review


The transient protein-protein interactions induced by guanine nucleotide-dependent conformational changes of G proteins play central roles in G protein-coupled receptor-mediated signaling systems. Leukemia-associated RhoGEF (LARG), a guanine nucleotide exchange factor for Rho, contains an RGS homology (RH) domain and Dbl homology/ pleckstrin homology (DH/PH) domains and acts both as a GTPase-activating protein (GAP) and an effector for G≤13. However, the molecular mechanism of LARG activation upon Gα13 binding is not yet well understood. In this study, we analyzed the Gα13-LARG interaction using cellular and biochemical methods, including a surface plasmon resonance (SPR) analysis. The results obtained using various LARG fragments demonstrated that active Gα13 interacts with LARG through the RH domain, DH/PH domains, and C-terminal region. However, an alanine substitution at the RH domain contact position in Gα13 resulted in a large decrease in affinity. Thermodynamic analysis revealed that binding of Gα13 proceeds with a large negative heat capacity change (δCp°), accompanied by a positive entropy change (δS°). These results likely indicate that the binding of Gα13 with the RH domain triggers conformational rearrangements between Gα13 and LARG burying an exposed hydrophobic surface to create a large complementary interface, which facilitates complex formation through both GAP and effector interfaces, and activates the RhoGEF. We propose that LARG activation is regulated by an induced-fit mechanism through the GAP interface of Gα 13.

Original languageEnglish
Pages (from-to)5000-5009
Number of pages10
JournalJournal of Biological Chemistry
Issue number8
Publication statusPublished - Feb 20 2009

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology


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