Computer-based redesign of a protein folding pathway

A fundamental test of our current understanding of protein folding is to ra tionally redesign protein folding pathways. We use a computer-based design strategy to switch the folding pathway of protein G, which normally involve s formation of the second, but not the first, beta -turn at the rate limiti ng step in folding. Backbone conformations and amino acid sequences that ma ximize the interaction density in the first beta -hairpin were identified, and two variants containing ii amino acid replacements were found to be sim ilar to4 kcal mol(-1) more stable than wild type protein G. Kinetic studies show that the redesigned proteins fold similar to 100x faster than wild ty pe protein and that the first beta -turn is formed and the second disrupted at the rate limiting step in folding.