Long-range molecular dynamics show that inactive forms of Protein Kinase A are more dynamic than active forms

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Protein kinases exist in active and inactive states, crucial for enzyme function.
• Protein dynamics are key to understanding enzyme mechanisms.
• Protein kinase A (PKA) is a vital enzyme involved in numerous cellular processes.

Purpose of the Study:

• To investigate the molecular dynamics of different protein kinase A (PKA) variants.
• To compare the dynamics between active and inactive PKA forms under various conditions.
• To elucidate the role of specific structural elements and modifications in PKA dynamics.

Main Methods:

• Microsecond molecular dynamics (MD) simulations were performed on six PKA variants.
• Simulations included variations in active/inactive states, ligand binding, C-terminal tail presence, and phosphorylation.
• Root mean square fluctuations (RMSF) were analyzed to quantify protein dynamics.

Main Results:

• Inactive PKA forms showed significantly higher root mean square fluctuations (RMSF) than active forms.
• Increased dynamics in inactive states were attributed to the ATP binding loop, catalytic loop, and αG helix.
• The presence of the C-terminal tail reduced dynamics in both active and inactive states.
• Phosphorylation status at Thr 197 did not alter the higher dynamics of the inactive form.

Conclusions:

• Inactive PKA states possess higher intrinsic dynamics compared to active states.
• The C-terminal tail stabilizes both active and inactive PKA conformations.
• The relative stability of active PKA may facilitate substrate binding and product release.
• Precise coordination required for phosphoryl group transfer is potentially aided by the stable active state.