(677e) Effects of Tethering a Multistate Folding Protein to a Surface

Tethering proteins to surfaces in a way that preserves function is key to making reliable protein chips and realizing many goals in biotechnology and personalized medicine, yet fundamental understanding of the relevant phenomena remains fragmented due to resolution limitations of experimental techniques. Molecular simulation has provided useful answers, but studies to date have focused solely on small, model proteins that fold through a two-state (folded/unfolded) mechanism.   Most proteins of practical relevance fold through a multistate mechanism with multiple intermediates, and the implications of these added states on tether site selection have not been examined previously. This study uses simulation to show how surfaces can affect proteins which folding through a multistate process by investigating the folding mechanism of lysozyme (PDB ID: 7LZM). The results demonstrate that in the bulk 7LZM folds through a process with four stable states: the folded state, the unfolded state, and two stable intermediates. The folding mechanism remains the same when the protein is tethered to a surface at most residues; however, in one case the folding mechanism changes in such a way as to eliminate one of the intermediates. An analysis of the molecular configurations shows that tethering at this site is advantageous for protein arrays because the active site is both presented to the bulk phase and stabilized. Taken as a whole, the results offer hope that rational design of protein arrays is possible once the behavior of the protein on the surface is ascertained.