8vyb
Cryo-EM structure of human core Rab3GAP1/2 complex
Structural highlights
DiseaseRB3GP_HUMAN Cataract-intellectual disability-hypogonadism syndrome;Micro syndrome. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. FunctionRB3GP_HUMAN Catalytic subunit of the Rab3 GTPase-activating (Rab3GAP) complex composed of RAB3GAP1 and RAB3GAP2, which has GTPase-activating protein (GAP) activity towards various Rab3 subfamily members (RAB3A, RAB3B, RAB3C and RAB3D), RAB5A and RAB43, and guanine nucleotide exchange factor (GEF) activity towards RAB18 (PubMed:10859313, PubMed:24891604, PubMed:9030515). As part of the Rab3GAP complex, acts as a GAP for Rab3 proteins by converting active RAB3-GTP to the inactive form RAB3-GDP (PubMed:10859313). Rab3 proteins are involved in regulated exocytosis of neurotransmitters and hormones (PubMed:15696165). The Rab3GAP complex, acts as a GEF for RAB18 by promoting the conversion of inactive RAB18-GDP to the active form RAB18-GTP (PubMed:24891604). Required for recruiting and activating RAB18 at the endoplasmic reticulum (ER) membrane where it maintains proper ER structure (PubMed:24891604). Required for normal eye and brain development (PubMed:15696165, PubMed:23420520). May participate in neurodevelopmental processes such as proliferation, migration and differentiation before synapse formation, and non-synaptic vesicular release of neurotransmitters (PubMed:9030515, PubMed:9852129).[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedThe heterodimeric Rab3GAP complex is a guanine nucleotide exchange factor (GEF) for the Rab18 GTPase that regulates lipid droplet metabolism, ER-to-Golgi trafficking, secretion, and autophagy. Why both subunits of Rab3GAP are required for Rab18 GEF activity and the molecular basis of how Rab3GAP engages and activates its cognate substrate are unknown. Here we show that human Rab3GAP is conformationally flexible and potentially autoinhibited by the C-terminal domain of its Rab3GAP2 subunit. Our high-resolution structure of the catalytic core of Rab3GAP, determined by cryo-EM, shows that the Rab3GAP2 N-terminal domain binds Rab3GAP1 via an extensive interface. AlphaFold3 modelling analysis together with targeted mutagenesis and in vitro activity assay reveal that Rab3GAP likely engages its substrate Rab18 through an interface away from the switch and interswitch regions. Lastly, we find that three Warburg Micro Syndrome-associated missense mutations do not affect the overall architecture of Rab3GAP but instead likely interfere with substrate binding. Biochemical and structural characterization of Rab3GAP reveals insights into Rab18 nucleotide exchange activity.,Fairlie GMJ, Nguyen KM, Nam SE, Shaw AL, Parson MAH, Shariati HR, Wang X, Jenkins ML, Gong M, Burke JE, Yip CK Nat Commun. 2025 Jan 8;16(1):479. doi: 10.1038/s41467-025-55828-8. PMID:39779760[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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