Intrinsically Disordered Proteins Can Behave as Different Polymers across Their Conformational Ensemble

Area of Science:

• Biophysics
• Computational Biology
• Protein Science

Background:

• Intrinsically disordered proteins (IDPs) lack stable 3D structures, exploring diverse conformations.
• Understanding IDP conformational heterogeneity is crucial for their function.

Purpose of the Study:

• To investigate the conformational space and dynamics of the intrinsically disordered protein beta-casein.
• To analyze the polymer scaling behavior and structural diversity within different energy funnels.

Main Methods:

• Hamiltonian replica exchange atomistic molecular dynamics (MD) simulations in explicit water.
• Analysis of energy landscapes and application of static polymeric scaling laws.
• Standard MD simulations in the NVT ensemble for representative conformations.

Main Results:

• Beta-casein's energy landscape features a global minimum and two shallow funnels.
• Different funnels exhibit distinct polymeric scaling exponents, indicating non-uniform behavior.
• Conformations near the global minimum are globular, while those near local minima are coil-like.
• Simulated dynamics show heterogeneous globule-to-coil-like signatures.

Conclusions:

• IDPs like beta-casein can adopt fundamentally different polymer characteristics in different conformational states.
• Structural diversity directly impacts the equilibrium dynamics of intrinsically disordered proteins.