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Published on: July 16, 2017
Allostery and dynamics in small G proteins
1Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, U.K. hrm28@cam.ac.uk.
Abstract:
The Ras family of small guanine nucleotide-binding proteins behave as molecular switches: they are switched off and inactive when bound to GDP but can be activated by GTP binding in response to signal transduction pathways. Early structural analysis showed that two regions of the protein, which change conformation depending on the nucleotide present, mediate this switch. A large number of X-ray, NMR and simulation studies have shown that this is an over-simplification. The switch regions themselves are highly dynamic and can exist in distinct sub-states in the GTP-bound form that have different affinities for other proteins. Furthermore, regions outside the switches have been found to be sensitive to the nucleotide state of the protein, indicating that allosteric change is more widespread than previously thought. Taken together, the accrued knowledge about small G protein structures, allostery and dynamics will be essential for the design and testing of the next generation of inhibitors, both orthosteric and allosteric, as well as for understanding their mode of action.
Insights
Ras proteins act as molecular switches, controlled by GDP/GTP binding. Advanced studies reveal complex dynamics and allosteric changes beyond simple switch regions, crucial for developing new inhibitors.
Area of Science:
- Molecular Biology
- Structural Biology
- Biochemistry
Background:
- Ras proteins function as molecular switches, cycling between inactive GDP-bound and active GTP-bound states.
- Initial models proposed simple conformational changes in two switch regions mediate this activation.
- Recent structural and dynamic studies challenge this simplified view.
Purpose of the Study:
- To provide a comprehensive overview of the structural dynamics and allosteric mechanisms of Ras proteins.
- To highlight the complexity of Ras protein regulation beyond the canonical switch regions.
- To inform the development of novel Ras-targeting therapeutics.
Main Methods:
- Review and synthesis of extensive X-ray crystallography, NMR spectroscopy, and molecular dynamics simulation data.
- Analysis of structural changes and dynamic properties of Ras proteins in different nucleotide-bound states.
- Integration of findings on protein-protein interactions and allosteric regulation.
Main Results:
- Ras switch regions are highly dynamic and exhibit multiple sub-states in the GTP-bound form.
- Allosteric effects extend beyond the switch regions, influencing protein behavior based on nucleotide status.
- The nucleotide-dependent conformational landscape is more intricate than previously understood.
Conclusions:
- A simplified two-state switch model for Ras proteins is insufficient to explain their behavior.
- Understanding the nuanced dynamics and widespread allostery is critical for rational drug design.
- Future inhibitor development should consider the complex structural and dynamic properties of Ras proteins.
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