title: Bacteriorhodopsin folds through a poorly organized transition state.
abstract: 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.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University , 575 Stadium Mall Drive, West Lafayette, Indiana 47907, United States.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Schlebach
authors.forename: Nicholas B
authors.initials: NB
authors.lastname: Woodall
authors.forename: James U
authors.initials: JU
authors.lastname: Bowie
authors.forename: Chiwook
authors.initials: C
authors.lastname: Park
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000235:genetics; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D009154:Mutation; D011489:Protein Denaturation; D017510:Protein Folding; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D012967:Sodium Dodecyl Sulfate; D001436:Bacteriorhodopsins