title: Probing the bottom of a folding funnel using conformationally gated electron transfer reactions.
abstract: The effect of global stability on the kinetics of interconversion between the native (N) and a compact, partially unfolded form (I) of iso-1-cytochrome c stabilized by His73-heme ligation is investigated using a novel conformationally gated ET method. For the K73H variant and the 2-fold less stable AcH73 variant, the N and I conformers are of nearly equal stability at pH 7.5. The pH jump kinetic data yield kobs = kNI + kIN of 35-40 s-1 at final pH values from 6 to 8 for the AcH73 variant, about 3-fold faster than for the more stable K73H variant. Gated ET measurements give kNI = 28 s-1 and kIN = 13 s-1 for the AcH73 variant, 10- and 2-fold greater than that for the more stable K73H variant. Thus, funneled landscapes have evolved such that loss of global stability lowers barriers at the bottom of a folding funnel, still allowing for efficient folding.
authors.affiliation: Department of Chemistry and Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, Montana 59812, USA.
authors.forename: Swati
authors.initials: S
authors.lastname: Bandi
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Bowler
mesh_terms: D045304:Cytochromes c / Q000737:chemistry*; D004579:Electron Transport; D006418:Heme / Q000737:chemistry; D006639:Histidine / Q000737:chemistry / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D009154:Mutation; D011487:Protein Conformation; D017510:Protein Folding
chemical_list: D008024:Ligands; D006418:Heme; D006639:Histidine; D045304:Cytochromes c