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Nucleotide binding switches the information flow in ras GTPases
Francesco Raimondi1, Guillem Portella, Modesto Orozco
1Department of Chemistry, University of Modena and Reggio Emilia, Modena, Italy.
Plos Computational Biology
|March 11, 2011
Summary
Guanine nucleotide-binding proteins (G proteins) exhibit distinct flexibility patterns when bound to GDP versus GTP. This study reveals that GDP-bound states show higher flexibility, crucial for Guanine Exchange Factor (GEF) interactions and nucleotide exchange.
Area of Science:
- Molecular Biology
- Biophysics
- Structural Biology
Background:
- The Ras superfamily of guanine nucleotide-binding proteins (G proteins) are critical regulators of intracellular signal transduction pathways.
- Understanding the dynamic behavior of these proteins in different nucleotide-bound states is essential for deciphering their regulatory mechanisms.
Purpose of the Study:
- To investigate the intrinsic flexibility patterns of five G proteins in their GDP-bound (S(GDP)) and GTP-bound (S(GTP)) states at atomic resolution.
- To compare the dynamic differences between small G proteins and Gα proteins in their inactive and active states.
Main Methods:
- Molecular Dynamics (MD) simulations were employed to analyze the flexibility of five G proteins in both GDP- and GTP-bound conformations.
- Functional mode analysis, dynamic domain identification, and interaction energy correlation analyses were performed.
Main Results:
- All investigated G proteins exhibited higher intrinsic flexibility in the S(GDP) state compared to the S(GTP) state.
- Significant dynamic differences were observed between small G proteins and Gα proteins, particularly in the inactive state.
- GDP binding enhanced flexibility in mechanically distinct domains involved in nucleotide exchange and promoted long-range allosteric communication in Gα proteins, unlike GTP binding.
Conclusions:
- The nucleotide-dependent flexibility of G proteins plays a crucial role in regulating signal transduction.
- GDP-bound states facilitate higher amplitude motions necessary for Guanine Exchange Factor (GEF) recognition and nucleotide exchange.
- Specific amino acid residues in switches I and II are dynamically involved in GEF recognition and influence the rate of GDP release.
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