Transient misfolding dominates multidomain protein folding.

Area of Science:

• Biochemistry
• Molecular Biology
• Protein Folding

Background:

• Multidomain proteins with homologous tandem repeats often have divergent neighboring sequences.
• This divergence is likely driven by evolutionary pressure to prevent misfolding and aggregation at high cellular protein concentrations.

Purpose of the Study:

• To investigate the mechanisms preventing misfolding between the immunoglobulin-like domains of titin.
• To understand the role of sequence divergence in mitigating protein misfolding.

Main Methods:

• Microfluidic-mixing single-molecule kinetics.
• Ensemble experiments.
• Molecular simulations.

Main Results:

• Over half of refolding tandem repeats transiently form diverse misfolded conformations, irrespective of sequence identity.
• A significant fraction of these misfolds resemble intramolecular amyloid-like states.
• Transient misfolds disappear more rapidly in naturally occurring domains with low sequence identity compared to identical domains.

Conclusions:

• Evolutionary sequence divergence between protein domains is crucial for suppressing long-lived, potentially harmful misfolded states.
• Cells tolerate large populations of transient misfolded states, suggesting a balance between folding efficiency and stability.