Touring the Protein Energy Landscape: The View Depends on Where and How You Look

Abstract

Decoding the information in the primary sequence of a protein is one of the most fundamental challenges in modern biology. A protein's sequence encodes more than just the native structure; it encodes the entire energy landscape – an ensemble of conformations whose energetics and dynamics are finely tuned. I will present developments in both our single molecule and ensemble studies probing high‐energy fluctuations on the energy landscape. In particular, we have use a novel method to explore the mechanical stability of single protein molecules in the low force regime of the laser tweezers. The low spring constant of the laser tweezers enables us to directly monitor low force refolding events and fluctuations between different molecular structures at quasi‐equilibrium conditions. Using this approach we have been able to identify and monitor novel events on the conformational energy landscape. Our recent results on the differences in mechanical compliance between the molten globule and native states and force‐dependent changes in the unfolding pathway of proteins have important implications for mechanical processes in the cell. I will also present our development of a thiol‐exchange method that allows partitioning of fluctuations and partially unfolded conformations to either side of the rate limiting step for unfolding.