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Structure of the GTPase-binding domain of Sec5 and elucidation of its Ral binding site

Abstract : The exocyst complex is involved in the final stages of exocytosis, when vesicles are targeted to the plasma membrane and dock. The regulation of exocytosis is vital for a number of processes, for example, cell polarity, embryogenesis, and neuronal growth formation. Regulation of the exocyst complex in mammals was recently shown to be dependent upon binding of the small G protein, Ral, to Sec5, a central component of the exocyst. This interaction is thought to be necessary for anchoring the exocyst to secretory vesicles. We have determined the structure of the Ral-binding domain of Sec5 and shown that it adopts a fold that has not been observed in a G protein effector before. This fold belongs to the immunoglobulin superfamily in a subclass known as IPT domains. We have mapped the Ral binding site on this domain and found that it overlaps with protein-protein interaction sites on other IPT domains but that it is completely different from the G protein-geranyl-geranyl interaction face of the Ig-like domain of the Rho guanine nucleotide dissociation inhibitor. This mapping, along with available site-directed mutagenesis data, allows us to predict how Ral and Sec5 may interact.
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2003-Mott_Journal of Biologica...
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Helen R Mott, Daniel Nietlispach, Louise J Hopkins, Gladys Mirey, Jacques H Camonis, et al.. Structure of the GTPase-binding domain of Sec5 and elucidation of its Ral binding site. Journal of Biological Chemistry, American Society for Biochemistry and Molecular Biology, 2003, 278 (19), pp.17053-17059. ⟨10.1074/jbc.M300155200⟩. ⟨hal-02683415⟩



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