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Related Concept Videos

Rab Proteins01:14

Rab Proteins

3.9K
Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
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Rab Cascades01:25

Rab Cascades

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Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
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Small GTPases - Ras and Rho01:24

Small GTPases - Ras and Rho

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Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:
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Leaky Scanning02:28

Leaky Scanning

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During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA.  Marilyn Kozak discovered that the sequence RCCAUGG (where R...
5.1K
Coat Assembly and GTPases01:33

Coat Assembly and GTPases

3.5K
Vesicles incorporate different coat protein subunits in different cell locations, which changes the properties of the coat, such as the shape and geometry of the transport vesicles. Thus, vesicle coat proteins also play a significant role in cargo selection.
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
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The Early Endosome: Endocytosis of Transferrin01:28

The Early Endosome: Endocytosis of Transferrin

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Essential proteins such as insulin or low-density lipoprotein (LDL) and micronutrients such as iron enter a eukaryotic cell through receptor-mediated endocytosis. Subsequently, the early endosomes fuse with the vesicles containing such receptor-ligand complexes and play a vital role in sorting the incoming ligands and receptors. While the ligands are either degraded inside the vesicle or released into the cytosol, their receptors are returned to the plasma membrane for further rounds of...
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Related Experiment Video

Updated: Jun 3, 2025

Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag
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Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

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Biochemical and structural characterization of Rab3GAP reveals insights into Rab18 nucleotide exchange activity.

Gage M J Fairlie1, Kha M Nguyen1, Sung-Eun Nam1

  • 1Life Sciences Institute, Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.

Nature Communications
|January 8, 2025
PubMed
Summary

The Rab3GAP complex activates Rab18 GTPase, crucial for cellular processes. Researchers elucidated its structure and substrate engagement mechanism, revealing insights into Warburg Micro Syndrome.

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Last Updated: Jun 3, 2025

Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag
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Rab10 Phosphorylation Detection by LRRK2 Activity Using SDS-PAGE with a Phosphate-binding Tag

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Area of Science:

  • Molecular Biology
  • Cell Biology
  • Structural Biology

Background:

  • The Rab3GAP complex functions as a guanine nucleotide exchange factor (GEF) for Rab18 GTPase.
  • Rab18 regulates critical cellular functions including lipid droplet metabolism, ER-to-Golgi trafficking, secretion, and autophagy.
  • The precise mechanisms underlying Rab3GAP's GEF activity and substrate interaction remain largely unknown.

Purpose of the Study:

  • To investigate the structural basis of Rab3GAP's function as a GEF for Rab18.
  • To understand how Rab3GAP engages and activates its substrate, Rab18.
  • To explore the impact of Warburg Micro Syndrome mutations on Rab3GAP structure and function.

Main Methods:

  • High-resolution cryo-electron microscopy (cryo-EM) to determine the structure of the Rab3GAP catalytic core.
  • AlphaFold3 modeling for computational analysis of protein structure and interactions.
  • Targeted mutagenesis and in vitro activity assays to assess protein function.

Main Results:

  • Human Rab3GAP exhibits conformational flexibility and potential autoinhibition by the Rab3GAP2 C-terminal domain.
  • The cryo-EM structure reveals an extensive interface between the Rab3GAP2 N-terminal domain and Rab3GAP1.
  • Analysis suggests Rab3GAP engages Rab18 via an interface distinct from the switch and interswitch regions.
  • Warburg Micro Syndrome mutations do not disrupt Rab3GAP architecture but likely impair substrate binding.

Conclusions:

  • The study provides a high-resolution structural model of the Rab3GAP catalytic core, detailing subunit interactions.
  • A novel mechanism for Rab18 substrate engagement by Rab3GAP is proposed, distinct from canonical GEF-substrate interactions.
  • Insights into how disease-associated mutations affect Rab3GAP function are provided, potentially impacting cellular processes regulated by Rab18.