Visualizing transient protein-folding intermediates by tryptophan-scanning mutagenesis.

Area of Science:

• Protein folding dynamics
• Biophysical characterization
• Structural biology

Background:

• Understanding protein folding, assembly, and function requires characterizing transient states.
• High-resolution techniques like NMR and X-ray crystallography struggle with short-lived protein states.

Purpose of the Study:

• To develop and apply a novel method for characterizing transient protein states.
• To investigate the folding mechanism of the small globular mammalian protein ubiquitin.

Main Methods:

• Introduced tryptophan residues at solvent-exposed positions.
• Measured fluorescence to assess the native-like, denatured-like, or non-native-like character of each position.
• Applied the method to a late-folding-intermediate state of ubiquitin.

Main Results:

• Successfully characterized a late-folding-intermediate state of ubiquitin.
• Identified productive non-native interactions within this intermediate state.
• The findings suggest a 'flycatcher' mechanism for concerted binding and folding.

Conclusions:

• Fluorescence measurements of introduced tryptophan residues offer a viable approach for studying transient protein states.
• The 'flycatcher' mechanism provides new insights into protein folding pathways.
• This method advances the study of protein dynamics and function.