title: A hydrophobic cluster forms early in the folding of dihydrofolate reductase.
abstract: The rapid kinetic phase that leads from unfolded species to transient folding intermediates in dihydrofolate reductase from Escherichia coli was examined by site-directed mutagenesis and by physicochemical means. The absence of this fluorescence-detected phase in the refolding of the Trp-74Phe mutant protein strongly implies that this early phase in refolding can be assigned to just one of the five Trp residues in the protein, Trp-74. In addition, water-soluble fluorescence quenching agents, iodide and cesium, have a much less significant effect on this early step in refolding than on the slower phases that lead to native and native-like conformers. These and other data imply that an important early event in the folding of dihydrofolate reductase is the formation of a hydrophobic cluster which protects Trp-74 from solvent.
authors.affiliation: Department of Chemistry, Pennsylvania State University, University Park 16802.
authors.forename: E P
authors.initials: EP
authors.lastname: Garvey
authors.forename: J
authors.initials: J
authors.lastname: Swank
authors.forename: C R
authors.initials: CR
authors.lastname: Matthews
mesh_terms: D001483:Base Sequence; D005453:Fluorescence; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D011487:Protein Conformation; D012995:Solubility; D013762:Tetrahydrofolate Dehydrogenase / Q000302:isolation & purification; D014364:Tryptophan
chemical_list: D014364:Tryptophan; D013762:Tetrahydrofolate Dehydrogenase