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Rab Proteins

Rab Proteins

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...

Rab Cascades

Rab Cascades

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.

Coat Assembly and GTPases

Coat Assembly and GTPases

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...

Small GTPases - Ras and Rho

Small GTPases - Ras and Rho

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:

Pinching-off of Coated Vesicles

Pinching-off of Coated Vesicles

Vesicle budding is orchestrated by distinct cytosolic proteins such as adaptor proteins, coat proteins, and GTPases. To initiate vesicle budding, membrane-bending proteins containing crescent-shaped BAR domains bind to the lipid heads in the bilayer and distort the membrane to form a protein-coated vesicle bud. Adaptors proteins such as AP2 for clathrin-coated vesicles can nucleate on the deformed membrane. Finally, coat proteins such as clathrin or COPI and COPII assemble into a coat forming...

GTPases and their Regulation

GTPases and their Regulation

Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...

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Related Experiment Video

Updated: Jun 27, 2026

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Published on: March 9, 2012

Large nucleotide-dependent conformational change in Rab28.

Sung Haeng Lee¹, Kyuwon Baek, Roberto Dominguez

¹Department of Physiology, University of Pennsylvania School of Medicine, 3700 Hamilton Walk, A507 Richards Building, Philadelphia, PA 19104-6085, USA.

|November 26, 2008

Summary

This summary is machine-generated.

Rab GTPases regulate membrane trafficking. Crystal structures reveal Rab28 undergoes significant conformational changes due to a unique double-glycine motif, impacting its activity.

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Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

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Published on: October 8, 2015

Area of Science:

Molecular biology
Structural biology
Cell biology

Background:

Rab GTPases are key regulators of intracellular membrane trafficking.
Understanding Rab GTPase structure-function relationships is crucial for cell biology.

Purpose of the Study:

To determine the crystal structures of Rab28 in its active and inactive states.
To investigate the structural basis for Rab28's function and its unique characteristics within the Rab family.

Main Methods:

X-ray crystallography
Protein structure determination at high resolution (1.5 and 1.1 Å)
Biochemical analysis of nucleotide-bound states (GppNHp and GDP-3'P)

Main Results:

High-resolution crystal structures of active (GppNHp-bound) and inactive (GDP-3'P-bound) Rab28 were obtained.
Rab28 exhibits a larger nucleotide-dependent conformational change compared to other Rab GTPases.
A unique double-glycine motif in switch 2 of Rab28 contributes to its increased flexibility.

Conclusions:

The distinct conformational flexibility of Rab28, influenced by the double-glycine motif, differentiates it from other Rab GTPases.
This motif, shared with the Arf family, may significantly affect Rab28's catalytic activities and regulatory roles.
Structural insights into Rab28 provide a foundation for understanding its specific role in membrane trafficking.