Microsecond protein folding through a compact transition state.

Published

Journal Article

Dynamic NMR methods have been employed to measure the folding and unfolding rate constants of two extremely fast-folding proteins. lambda 6-85, a truncated, monomeric form of the N-terminal domain of lambda repressor, refolds with a lifetime of approximately 250 microseconds. These methods have also been applied to a thermostable lambda 6-85 variant with alanine substituted for glycine residues 46 and 48 in the third helix (G46A/G48A). Both proteins exhibit linear ln (kf,u) versus [urea] plots, consistent with two-state folding for both proteins. When extrapolated to 0M urea, the data indicate that G46A/G48A folds with a lifetime of less than 20 microseconds. The slopes of the ln (kf,u) versus [urea] curves (mu and mf) indicate that the modest Gly-->Ala double mutation dramatically changes the transition state solvent accessibility. The transition state for lambda 6-85 has a fractional accessibility (mu/(mu-mf)) of 0.61, whereas the transition state for G46A/G48A is much more native-like, with a fractional accessibility of 0.16. The extraordinary change in the folding pathway that these mutations induce suggests that the intrinsic stability of helix 3 is an important determinant of the folding mechanism.

Full Text

Duke Authors

Cited Authors

  • Burton, RE; Huang, GS; Daugherty, MA; Fullbright, PW; Oas, TG

Published Date

  • October 25, 1996

Published In

Volume / Issue

  • 263 / 2

Start / End Page

  • 311 - 322

PubMed ID

  • 8913309

Pubmed Central ID

  • 8913309

International Standard Serial Number (ISSN)

  • 0022-2836

Digital Object Identifier (DOI)

  • 10.1006/jmbi.1996.0577

Language

  • eng

Conference Location

  • England