Coupled folding and binding with 2D Window-Exchange Umbrella Sampling.

Area of Science:

• Biophysics
• Computational Biology
• Structural Biology

Background:

• Intrinsically disordered proteins gain structure through partner binding, a process known as coupled folding and binding (CFaB).
• CFaB is vital for numerous biological functions.
• Traditional simulation methods struggle to sample the rare transition states of CFaB.

Purpose of the Study:

• To investigate the coupled folding and binding of HdeA monomers at neutral pH using an advanced simulation technique.
• To characterize the transition state ensemble of this extremely rare process.

Main Methods:

• Utilized a variant of Umbrella Sampling, specifically Window-Exchange Umbrella Sampling, to enhance sampling of rare events.
• Applied high-resolution sampling in the transition state region to analyze the HdeA dimer formation.
• Clustered states along the principal transition path to describe the binding and folding process.

Main Results:

• Successfully sampled and detailed the transition states of HdeA monomer CFaB.
• Provided a high-resolution description of the HdeA dimer formation, revealing accessible states for client recognition.
• Demonstrated that window exchanges significantly improve relaxation in orthogonal variables.

Conclusions:

• Window-Exchange Umbrella Sampling is a powerful method for studying flexible binding systems.
• This approach enables detailed characterization of transition state ensembles for rare biological processes.
• The findings offer new insights into the dynamics of intrinsically disordered proteins and their interactions.