How to Untie a Protein Knot

Area of Science:

• Biochemistry
• Structural Biology
• Evolutionary Biology

Background:

• The evolutionary origins of protein topological knots are not well understood.
• Knotted protein structures present unique challenges in protein folding and function.
• Understanding knot formation is crucial for deciphering protein evolution.

Purpose of the Study:

• To investigate the evolutionary origin of protein backbone threading through topological knots.
• To determine how knotted proteins achieve their stable, complex structures.
• To explore the functional implications of protein knotting.

Main Methods:

• Utilized circular permutation to experimentally 'untie' a naturally occurring knotted protein.
• Analyzed the structural and energetic consequences of altering the protein's topology.
• Investigated the role of domain swapping in knot resolution.

Main Results:

• Demonstrated that circular permutation can effectively resolve a protein knot.
• Showed that a domain-swapped dimer intermediate releases the topological knot.
• Identified that knot release is associated with the alleviation of a high-energy state.

Conclusions:

• Protein knots may evolve through mechanisms that allow for their transient formation and resolution.
• Domain-swapped dimers represent a potential pathway for untying knotted proteins during evolution.
• Resolving protein knots can reduce energetic barriers, potentially facilitating substrate binding and function.