Related Experiment Video

Updated: May 15, 2026

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells
10:27

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

Published on: March 9, 2012

RAC1P29S is a spontaneously activating cancer-associated GTPase

Matthew J Davis1, Byung Hak Ha, Edna C Holman

  • 1Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA.

Proceedings of the National Academy of Sciences of the United States of America
|January 4, 2013
PubMed

Insights

A new melanoma mutation, RAC1(P29S), activates the Rho family GTPase differently than Ras proteins. This gain-of-function mutation represents a novel cancer-related GTPase activity.

Area of Science:

  • Oncology
  • Molecular Biology
  • Biochemistry

Background:

  • Ras-related C3 botulinum toxin substrate 1 (RAC1) is a GTPase involved in cell signaling.
  • Gain-of-function mutations in RAC1 are increasingly identified in melanoma, with RAC1(P29S) being the third most frequent.
  • Unlike Ras GTPases, Rho family GTPases rarely exhibit cancer-associated mutations.

Purpose of the Study:

  • To investigate the activation mechanism of the melanoma-associated RAC1(P29S) mutation.
  • To compare the activation of RAC1(P29S) with other known RAC1 mutants and oncogenic Ras proteins.

Main Methods:

  • Determination and comparison of crystal structures of activated RAC1 GTPases.
  • Biochemical analysis of GTPase activity and nucleotide exchange rates.

Main Results:

  • The RAC1(P29S) mutant exhibits spontaneous activation through increased GDP/GTP nucleotide exchange, unlike Ras proteins that are typically activated by impaired GTP hydrolysis.
  • RAC1(P29S) and RAC1(F28L) mutants activate RAC1 through distinct mechanisms.
  • The activation mechanism of RAC1(P29S) differs from common oncogenic mutations in Ras-like GTPases that inhibit GTP hydrolysis.

Conclusions:

  • The RAC1(P29S) mutation represents a novel class of gain-of-function mutations in GTPases.
  • Understanding this unique activation mechanism may offer new therapeutic strategies for melanoma.

More Related Videos

RhoC GTPase Activation Assay09:58

RhoC GTPase Activation Assay

Published on: August 22, 2010

Bioluminescence Resonance Energy Transfer (BRET)-Based Assay for Measuring Interactions of CRAF with 14-3-3 Proteins in Live Cells06:44

Bioluminescence Resonance Energy Transfer (BRET)-Based Assay for Measuring Interactions of CRAF with 14-3-3 Proteins in Live Cells

Published on: March 1, 2024

Related Concept Videos

The Ras Gene02:38

The Ras Gene

The Ras-gene-encoded proteins are regulators of signaling pathways controlling cell proliferation, differentiation, or cell survival. The Ras-gene family in humans constitutes three primary members—the HRas, NRas, and KRas. These genes code for four functionally distinct yet closely related proteins—the HRas, NRas, KRas4A, and KRas4B. The involvement of mutant Ras genes in human cancer was first discovered in 1982 and is among the most common causes of human tumorigenesis.
Ras is a superfamily...
Small GTPases - Ras and Rho01:24

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:
MAPK Signaling Cascades01:07

MAPK Signaling Cascades

Mitogen-activated protein kinase, or MAPK pathway, activates three sequential kinases to regulate cellular responses such as proliferation, differentiation, survival, and apoptosis. The canonical MAPK pathway starts with a mitogen or growth factor binding to an RTK. The activated RTKs stimulate Ras, which recruits Raf or MAP3 Kinase (MAPKKK), the first kinase of the MAPK signaling cascade. Raf further phosphorylates and activates MEK or MAP2 Kinases (MAPKK), which in turn phosphorylates MAP...
Rab Proteins01:14

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...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
Cancer-Critical Genes I: Proto-oncogenes01:33

Cancer-Critical Genes I: Proto-oncogenes

Genes usually encode proteins necessary for the proper functioning of a healthy cell. Mutations can often cause changes to the gene expression pattern, thereby altering the phenotype.
When the function of certain critical genes, especially those involved in cell cycle regulation and cell growth signaling cascades, gets disrupted, it upsets the cell cycle progression. Such cells with unchecked cell cycles start proliferating uncontrollably and eventually develop into tumors.
Such genes that act...