Accounting for a mirror-image conformation as a subtle effect in protein folding

Area of Science:

• Biophysics
• Computational Biology
• Protein Folding

Background:

• Staphylococcal protein A's B domain is a model system for studying protein folding.
• Understanding the formation of non-native conformations is crucial for protein science.

Purpose of the Study:

• To elucidate the molecular mechanisms behind the mirror-image conformation formation in staphylococcal protein A.
• To investigate the dynamics of protein folding pathways and conformational transitions.

Main Methods:

• Molecular dynamics (MD) simulations using a coarse-grained united-residue force field.
• Analysis of local (free-energy profiles, chemical shifts) and global (principal component analysis) dynamics.
• Examination of protein-folding trajectories.

Main Results:

• Identified slow formation of the second loop and part of the third helix (Asp29-Asn35) as the primary cause of the mirror-image conformation.
• Demonstrated that mirror-image topology arises from subtle local interactions.
• Proposed a mechanism for overcoming the energy barrier between the metastable mirror-image and native states.

Conclusions:

• Local conformational states significantly influence protein folding pathways.
• Staphylococcal protein A's native state is favored over the energetically compatible mirror-image state due to specific dynamic mechanisms.
• The study provides insights into how proteins navigate complex energy landscapes to achieve their functional conformations.