A survey of lambda repressor fragments from two-state to downhill folding

Area of Science:

• Protein dynamics and biophysics
• Molecular biology and protein engineering

Background:

• Understanding protein folding is crucial for molecular biology.
• The transition between two-state and downhill folding pathways remains an active area of research.

Purpose of the Study:

• To investigate the two-state to downhill folding transition in lambda(6-85)* mutants.
• To explore the relationship between protein stability, folding rates, and folding mechanisms.

Main Methods:

• Examined 20 lambda(6-85)* mutants with varying stabilities and folding rates.
• Engineered four new mutants using core remodeling and frustratometer techniques.
• Determined melting temperatures and analyzed folding kinetics.
• Obtained X-ray crystal structure of a fast-folding mutant fragment.

Main Results:

• Identified a correlation between melting temperature and downhill folding across mutants.
• Observed a fast molecular phase with temperature-dependent amplitude in engineered proteins.
• Fast-folding mutants exhibited high melting temperatures (up to 80°C).
• X-ray structure revealed enhanced rigidity in a fast-folding mutant fragment.

Conclusions:

• Melting temperature is a key predictor of downhill folding propensity.
• Protein engineering strategies can accelerate folding rates.
• Enhanced rigidity in specific regions may contribute to faster protein folding.