Related Experiment Videos
Ras/Rap effector specificity determined by charge reversal
1Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Dortmund, Germany.
Abstract:
Members of the Ras subfamily of small GTP-binding proteins have been shown to be promiscuous towards a variety of putative effector molecules such as the protein kinase c-Raf and the Ral-specific guanine nucleotide exchange factor (Ral-GEF). To address the question of specificity of interactions we have introduced the mutations E30D and K31E into Rap and show biochemically, by X-ray structure analysis and by transfection in vivo that the identical core effector region of Ras and Rap (residues 32-40) is responsible for molecular recognition, but that residues outside this region are responsible for the specificity of the interaction. The major determinant for the switch in specificity is the opposite charge of residue 31--Lys in Rap, Glu in Ras--which creates a favourable complementary interface for the Ras-Raf interaction.
Insights
Small GTP-binding proteins like Ras and Rap interact with effectors. Mutations revealed that while the core effector region is conserved, specific residues outside this region dictate interaction specificity, particularly residue 31.
Area of Science:
- Molecular biology
- Biochemistry
- Structural biology
Background:
- Ras subfamily proteins are small GTP-binding proteins.
- These proteins interact with various effector molecules, including c-Raf and Ral-GEF.
- The specificity of these interactions is not fully understood.
Purpose of the Study:
- To investigate the molecular determinants of specificity in Ras-family protein interactions.
- To understand how mutations affect the interaction specificity between Ras and Rap proteins with their effectors.
Main Methods:
- Biochemical assays to study protein interactions.
- X-ray crystallography to determine protein structures.
- In vivo transfection studies to assess protein function.
Main Results:
- The core effector region (residues 32-40) of Ras and Rap is identical and responsible for molecular recognition.
- Residues outside this core region determine the specificity of interactions.
- A key determinant of specificity is residue 31, with Lys in Rap and Glu in Ras, influencing the Ras-Raf interaction.
Conclusions:
- Specificity of Ras subfamily protein interactions is governed by residues outside the conserved core effector region.
- Residue 31 plays a critical role in dictating the specificity of interactions, particularly for the Ras-Raf pathway.
- Understanding these specificity determinants is crucial for deciphering signaling pathways involving small GTP-binding proteins.