The Interplay of Conservation and Correlation in Enzyme Stability
Chemistry, The Ohio State University
(November 25, 2013 3:00 PM - 3:50 PM)
Despite remarkable advances in protein structure prediction and design, an accurate predictive model of the thermodynamic effects of even point mutations remains elusive. The post-genomic era is a remarkable time to consider the problem of protein stability from a statistical perspective. How is information distributed in protein sequences? What protein properties are encoded by conserved and co-varying amino acids? And how can we use this information to engineer more stable proteins? We have been analyzing the effects of sequence conservation and correlation on enzyme function and physical properties, by engineering consensus and correlated mutations, or fully consensus variants, of the ubiquitous and well-studied metabolic enzymes triosephosphate isomerse (TIM) and adenylate kinase (ADK). We have established useful methods for calculating and visualizing conservation and correlation. From two consensus variants of TIM, we showed that correlated networks in weakly conserved positions can contribute strongly to protein biophysical properties. We also showed that consensus mutations are more likely to stabilize at more conserved positions, unless those positions strongly co-vary with other positions. I will review these results and discuss further efforts to refine our sequence-based algorithm for protein stabilization, and establish its generality. I will also briefly discuss experiments to explore the effects of correlated mutations directly, including through the use of a TIM-knockout based selection we pioneered in our lab.