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Updated: Aug 23, 2026

Strategic Screening and Characterization of the Visual GPCR-mini-G Protein Signaling Complex for Successful Crystallization
Published on: March 16, 2020
Crystal structure of Rab9 complexed to GDP reveals a dimer with an active conformation of switch II
Julia G Wittmann1, Markus G Rudolph
1Department of Molecular Structural Biology and GZMB, Justus-von-Liebig-Weg 11, Georg-August University, 37077 Göttingen, Germany.
Abstract:
The small GTPase Rab9 is an essential regulator of vesicular transport from the late endosome to the trans-Golgi network, as monitored by the redirection of the mannose-6-phosphate receptors. The crystal structure of Rab9 complexed to GDP, Mg(2+), and Sr(2+) reveals a unique dimer formed by an intermolecular beta-sheet that buries the switch I regions. Surface area and shape complementarity calculations suggest that Rab9 dimers can form an inactive, membrane-bound pool of Rab9 . GDP that is independent of GDI. Mg(2+)-bound Rab9 represents an inactive state, but Sr(2+)-bound Rab9 . GDP displays activated switch region conformations, mimicking those of the GTP state. A hydrophobic tetrad is formed resembling an effector-discriminating epitope found only in GTP-bound Rab proteins.
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