title: The single helix in protein L is largely disrupted at the rate-limiting step in folding.
abstract: To investigate the role of helix formation in the folding of protein L, a 62 residue alpha/beta protein, we studied the consequences of both single and multiple mutations in the helix on the kinetics of folding. A triple mutant with 11 additional carbon atoms in core residues in the amino-terminal portion of the helix folded substantially faster than wild type, suggesting that hydrophobic association with residues elsewhere in the protein occurs at the rate-limiting step in folding. However, helix-destabilizing mutations had little effect on the rate of folding; in particular, a triple glycine substitution on the solvent-exposed side of the helix increased the unfolding rate 56-fold while reducing the folding rate less than threefold. Thus, in contrast to the predictions of models of folding involving the coalescence of well-formed secondary structure elements, the single helix in protein L appears to be largely disrupted at the rate-limiting step in folding and unfolding.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA, 98195, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Kim
authors.forename: Q
authors.initials: Q
authors.lastname: Yi
authors.forename: S T
authors.initials: ST
authors.lastname: Gladwin
authors.forename: J M
authors.initials: JM
authors.lastname: Goldberg
authors.forename: D
authors.initials: D
authors.lastname: Baker
mesh_terms: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins / Q000737:chemistry*; D007700:Kinetics; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C116593:L-protein, Peptococcus magnus; D011506:Proteins