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Using D-Amino Acids to Delineate the Mechanism of Protein Folding: Application to Trp-cage.

ABSTRACT: Using the miniprotein Trp-cage as a model, we show that D-amino acids can be used to facilitate the delineation of protein folding mechanism. Specifically, we study the folding-unfolding kinetics of three Trp-cage mutants where the native glycine residue near the C-terminus of the ?-helix is replaced by a D-amino acid. A previous study showed that these mutations increase the Trp-cage stability, due to a terminal capping effect. Our results show that the stabilizing effect of D-asparagine and D-glutamine originates almost exclusively from a decrease in the unfolding rate, while the D-alanine mutation results in a similar decrease in the unfolding rate, but it also increases the folding rate. Together, these results support a folding mechanism wherein the ?-helix formation in the transition state is nucleated at the N-terminus, whereas those long-range native interactions stabilizing this helix are developed at the downhill side of the folding free energy barrier.

SUBMITTER: Culik RM

PROVIDER: S-EPMC3844134 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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Using D-Amino Acids to Delineate the Mechanism of Protein Folding: Application to Trp-cage.

Culik Robert M RM Annavarapu Srinivas S Nanda Vikas V Gai Feng F

Chemical physics 20130801

Using the miniprotein Trp-cage as a model, we show that D-amino acids can be used to facilitate the delineation of protein folding mechanism. Specifically, we study the folding-unfolding kinetics of three Trp-cage mutants where the native glycine residue near the C-terminus of the α-helix is replaced by a D-amino acid. A previous study showed that these mutations increase the Trp-cage stability, due to a terminal capping effect. Our results show that the stabilizing effect of D-asparagine and D- ...[more]

PMID: 24307748

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