2ocy
From Proteopedia
Complex of the guanine exchange factor Sec2p and the Rab GTPase Sec4p
Structural highlights
Function[SEC2_YEAST] Guanine nucleotide exchange factor for SEC4, catalyzing the dissociation of GDP from SEC4 and also potently promoting binding of GTP. Activation of SEC4 by SEC2 is needed for the directed transport of vesicles to sites of exocytosis. Binds the Rab GTPase YPT32, but does not have exhange activity on YPT32.[1] [2] [3] [SEC4_YEAST] Involved in exocytosis. Maybe by regulating the binding and fusion of secretory vesicles with the cell surface. The GTP-bound form of SEC4 may interact with an effector, thereby stimulating its activity and leading to exocytotic fusion. SEC4 may be an upstream activator of the 19.5S SEC8/SEC15 particle. SEC4 probably interacts directly with SEC8; it could serve as the attachment site for the SEC8/SEC15 particle.[4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedRab GTPases, the largest subgroup in the superfamily of Ras-like GTPases, play regulatory roles in multiple steps of intracellular vesicle trafficking. They are activated by guanine nucleotide exchange factors (GEFs), which catalyze the interconversion of the GDP-bound, or inactive, form of Rab to the GTP-bound, or active, form. Relatively little is known of the mechanisms by which GEFs activate Rabs. Here, we present the crystal structure of the GEF domain of Sec2p in complex with its Rab partner Sec4p. The Sec2p GEF domain is a 220 Angstroms long coiled coil, striking in its simplicity and in the use of the coiled-coil motif for catalysis. The structure suggests a mechanism whereby Sec2p induces extensive structural rearrangements in the Sec4p switch regions and phosphate-binding loop that are incompatible with nucleotide binding. We show that Sec2p is specific for Sec4p and that specificity determinants reside in the two switch regions of Sec4p. A catalytic coiled coil: structural insights into the activation of the Rab GTPase Sec4p by Sec2p.,Dong G, Medkova M, Novick P, Reinisch KM Mol Cell. 2007 Feb 9;25(3):455-62. PMID:17289591[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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