Induction of flexibility through protein-protein interactions

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• The dimerization/docking (D/D) domain of cyclic AMP-dependent protein kinase (PKA) is crucial for enzyme localization via interactions with kinase anchoring proteins (AKAPs).
• AKAPs scaffold PKA, and AKAP-D/D complexes reveal AKAP binding within a hydrophobic groove on the D/D domain.

Purpose of the Study:

• To analyze changes in hydrogen/deuterium (H/D) exchange protection and backbone dynamics of the PKA D/D domain upon binding to the AKAP Ht31(pep).

Main Methods:

• Hydrogen/deuterium exchange mass spectrometry was used to assess backbone protection.
• Analysis of internal motions and flexibility changes in the D/D domain.

Main Results:

• Complex formation led to modest increases in H/D exchange protection across the D/D domain.
• Increased backbone flexibility was observed throughout the D/D domain, notably within the hydrophobic binding groove.

Conclusions:

• High-affinity binding paradoxically increases D/D domain flexibility and offers marginal H/D protection.
• This suggests a potential general mechanism for stabilizing hydrophobic interactions in protein-ligand complexes.