title: Thermodynamics and kinetics of non-native interactions in protein folding: a single point mutant significantly stabilizes the N-terminal domain of L9 by modulating non-native interactions in the denatured state.
abstract: Comparatively little is known about the role of non-native interactions in protein folding and their role in both folding and stability is controversial. We demonstrate that non-native electrostatic interactions involving specific residues in the denatured state can have a significant effect upon protein stability and can persist in the transition state for folding. Mutation of a single surface exposed residue, Lys12 to Met, in the N-terminal domain of the ribosomal protein L9 (NTL9), significantly increased the stability of the protein and led to faster folding. Structural and energetic studies of the wild-type and K12M mutant show that the 1.9 kcal mol(-1) increase in stability is not due to native state effects, but rather is caused by modulation of specific non-native electrostatic interactions in the denatured state. pH dependent stability measurements confirm that the increased stability of the K12M is due to the elimination of favorable non-native interactions in the denatured state. Kinetic studies show that the non-native electrostatic interactions involving K12 persist in the transition state. The analysis demonstrates that canonical Phi-values can arise from the disruption of non-native interactions as well as from the development of native interactions.
authors.affiliation: Graduate Program in Biochemistry and Structural Biology, State University of New York at Stony Brook, Stony Brook, NY 11794-5230, USA.
authors.forename: Jae-Hyun
authors.initials: JH
authors.lastname: Cho
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sato
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Raleigh
mesh_terms: D008239:Lysine / Q000737:chemistry; D008958:Models, Molecular; D017354:Point Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000235:genetics*; D013816:Thermodynamics; D014508:Urea / Q000737:chemistry
chemical_list: D012269:Ribosomal Proteins; C049650:ribosomal protein L9; D014508:Urea; D008239:Lysine