Related Experiment Video
Updated: Apr 3, 2026

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
11.3K
Ras p21 proteins with high or low GTPase activity can efficiently transform NIH/3T3 cells.
Cell
|February 28, 1986
Summary
Ras p21 mutants can gain transforming properties without reduced GTPase activity. This study shows efficient transformation can occur through alternative mechanisms, challenging previous assumptions about ras oncogene activation.
Area of Science:
- Molecular Biology
- Oncology
- Cell Biology
Background:
- Ras p21 proteins are key regulators of cell signaling.
- Reduced GTPase activity of ras p21 mutants is often linked to oncogenic transformation.
- The precise mechanisms driving ras-mediated transformation require further elucidation.
Purpose of the Study:
- To investigate the relationship between in vitro GTPase activity and transforming properties of ras p21 mutants.
- To determine if decreased GTPase activity is a universal requirement for ras p21-driven cellular transformation.
Main Methods:
- In vitro GTPase activity assays were performed on normal and mutant H-ras p21 proteins.
- Bacterially expressed normal H-ras p21 and various p21 mutants were microinjected into NIH/3T3 cells.
- Cellular morphologic alterations and DNA synthesis were assessed post-microinjection.
- Transforming activity of mutants expressed in eukaryotic vectors was compared to normal H-ras.
Main Results:
- Mutants H-ras p21-[Lys12-Ala59] and H-ras p21-[Arg12-Thr59] showed significantly lower in vitro GTPase activity compared to normal H-ras p21-[Gly12-Ala59] and H-ras p21-[Gly12-Thr59].
- Low concentrations of p21 mutants induced NIH/3T3 cell morphologic changes and DNA synthesis, unlike normal p21.
- Mutant ras p21 proteins exhibited transforming activity at least 100-fold greater than the normal H-ras gene.
Conclusions:
- Efficient transforming properties of ras p21 proteins can be activated independently of reduced in vitro GTPase activity.
- These findings suggest alternative pathways for ras oncogene activation and transformation.
- The study challenges the paradigm that diminished GTPase function is essential for ras-driven oncogenesis.
Related Concept Videos
Negative Regulator Molecules
39.0K
Positive regulators allow a cell to advance through cell cycle checkpoints. Negative regulators have an equally important role as they terminate a cell’s progression through the cell cycle—or pause it—until the cell meets specific criteria.
39.0K
GTPases and their Regulation
10.3K
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,...
Large G-proteins,...
10.3K
The Ras Gene
7.5K
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...
Ras is a...
7.5K
GTPases and their Regulation
3.3K
No description available
3.3K
Small GTPases - Ras and Rho
5.7K
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:
Three regulatory proteins control their activity:
5.7K
Activation and Inactivation of G Proteins
12.4K
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...
12.4K

