Using D-amino acids to delineate the mechanism of protein folding: Application to Trp-cage

作者：Culik Robert M; Annavarapu Srinivas; Nanda Vikas^*; Gai Feng

来源：Chemical Physics, 2013, 422: 131-134.

DOI：10.1016/j.chemphys.2013.01.021

• Protein folding
• D-amino acid
• T-jump
• Infrared

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 alpha-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 alpha-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.

• 出版日期2013-8-30