Bacteriorhodopsin folds through a poorly organized transition state.
- Author(s): Schlebach, Jonathan P
- Woodall, Nicholas B
- Bowie, James U
- Park, Chiwook
- et al.
Published Web Locationhttps://doi.org/10.1021/ja508359n
The folding mechanisms of helical membrane proteins remain largely uncharted. Here we characterize the kinetics of bacteriorhodopsin folding and employ φ-value analysis to explore the folding transition state. First, we developed and confirmed a kinetic model that allowed us to assess the rate of folding from SDS-denatured bacteriorhodopsin (bRU) and provides accurate thermodynamic information even under influence of retinal hydrolysis. Next, we obtained reliable φ-values for 16 mutants of bacteriorhodopsin with good coverage across the protein. Every φ-value was less than 0.4, indicating the transition state is not uniquely structured. We suggest that the transition state is a loosely organized ensemble of conformations.