pH-dependent structural diversity of profilin allergens determines thermal stability

Area of Science:

• Biochemistry
• Immunology
• Computational Biology

Background:

• Profilins are conserved eukaryotic proteins involved in actin dynamics.
• They are a common source of cross-reactive allergens, triggering Immunoglobulin E (IgE) antibody responses.
• Despite structural similarity, profilins exhibit diverse biophysical properties like thermal and pH stability.

Purpose of the Study:

• To investigate the origins of differing biophysical properties among profilin allergens (Amb a 8, Art v 4, Bet v 2).
• To elucidate the role of pH-dependent conformational flexibility in profilin allergen stability.

Main Methods:

• Constant pH molecular dynamics simulations.
• Gaussian accelerated molecular dynamics (MD) simulations.
• Analysis of conformational flexibility using residue-wise B-factors and dihedral entropies.

Main Results:

• Distinct differences in conformational flexibility were observed at varying pH levels, correlating with experimental melting temperatures.
• Protonation-dependent conformational ensembles were identified.
• Flexibility variations were linked to shifts in the conformational landscape.

Conclusions:

• Conformational flexibility, influenced by pH-dependent protonation, is a critical determinant of profilin allergen thermal stability.
• Considering solution-state, protonation-dependent conformational ensembles is essential for understanding biophysical differences in structurally similar allergens.