Conformation spaces of proteins.

Area of Science:

• Computational Biology
• Biophysics
• Structural Biology

Background:

• Understanding protein conformational space is crucial for deciphering protein folding mechanisms.
• Existing methods may not adequately capture the dynamics and scale of conformational exploration.
• Diverse ensembles from molecular dynamics, modeling, and structure determination require unified analysis.

Purpose of the Study:

• To introduce a novel, simple method for quantifying accessible conformational space in protein ensembles.
• To model protein conformational space as an N-dimensional hypercube for efficient analysis.
• To validate the N-cube method across various time scales and protein states.

Main Methods:

• Representing protein conformations as points in high-dimensional Euclidean space.
• Modeling this space as an N-dimensional hypercube defined by dimensions and edge length.
• Utilizing root-mean squared (RMSD) cartesian distances to define conformationally effective degrees of freedom.

Main Results:

• The N-cube method successfully measures conformational space size and shape across 10 orders of magnitude in time.
• Identified distinct conformational features: vibrational minima (0.1-1 ps), persistent states (1-100 ps), and transitions (ns).
• Calculated length scales for these events range from 0.2 Å to 2 Å.

Conclusions:

• The accessible folding space for villin suggests capacity for ~10^9 short-lived minima.
• The native state comprises ~10^2 thermally accessible minima.
• Random exploration predicts millisecond folding, but experimental times (microseconds) suggest a folding funnel accelerates the process.