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Dynamic binding of PKA regulatory subunit RI alpha
Justin Gullingsrud1, Choel Kim, Susan S Taylor
1Department of Chemistry and Biochemistry, University of California, San Diego, California 92093, USA. jgulling@mccammon.ucsd.edu
Structure (London, England : 1993)
|January 13, 2006
Summary
Regulatory subunit RIalpha of PKA undergoes significant conformational changes. Molecular dynamics reveal how its intrinsic flexibility and interactions stabilize complex formation with the catalytic subunit.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Recent crystal structures show regulatory subunit RIalpha of Protein Kinase A (PKA) undergoes substantial conformational changes.
- These changes occur upon complex formation with the catalytic subunit of PKA.
Purpose of the Study:
- To investigate the role of intrinsic conformational flexibility in RIalpha.
- To elucidate the contribution of interactions with the catalytic subunit to complex formation and stabilization.
Main Methods:
- Molecular dynamics (MD) simulations were employed.
- Simulations included a single RIalpha nucleotide binding domain (NBD) and a model complex of RIalpha NBDs with the catalytic subunit.
Main Results:
- A single RIalpha NBD, lacking cAMP, exhibited spontaneous shifts in its C helix between two conformations: one packed against the domain and another extended.
- This C helix extension was not observed in simulations of RIalpha NBDs lacking the catalytic subunit.
- In a model complex, conserved residues at the NBD interface stabilized the complex through interactions with the catalytic subunit.
Conclusions:
- Intrinsic conformational flexibility of RIalpha, particularly the C helix, plays a crucial role in PKA complex dynamics.
- Interactions between conserved residues at the NBD interface and the catalytic subunit are key for stabilizing the PKA holoenzyme structure.
- The findings align with existing experimental data, providing a molecular basis for PKA regulation.