Dynamics and cooperativity of Trp-cage folding

In this study, multiple independent molecular dynamics (MD) simulations on Trp-cage folding were performed at 300, 325 and 375 K using generalized Born (GB) implicit solvent model. The orientational movement of the side-chain of Trp6 to form a hydrophobic core with 3(10)-helix was observed. The breaking/formation of a salt bridge between Asp9 and Arg16 was proposed to be the prerequisite for Trp-cage folding/refolding. Our results demonstrate that the cooperation between the salt bridge and the Trp6 orientation leads to a stable tertiary structure of Trp-cage. Analyses on backbone concerted motions at different temperatures indicate that interactions between Trp6 and 3(10)-helix & Pro18 and between Pro12 and Pro17 & Pro18 are weakened at 375 K but strengthened at lower temperatures, suggesting that they could be the potential driving force of hydrophobic collapse. (C) 2008 Elsevier Inc. All rights reserved.