邀请人：Erdal C. Oğuz（ecoguz@iphy.ac.cn）

报告摘要：
Most of our understanding of the activity and specificity of enzymes focuses on their active site, which is a small part of their structure in direct interaction with the substrate. Yet, as illustrated by many examples of protein engineering success and failure, enzymatic function often depends crucially on residues away from the active site. Using the well-known example of serine proteases, which display such poorly understood yet pervasive long-range effects, we explore the sequence-function relationship systematically through large-scale experiments and statistical evolutionary analysis. I will present an experimental approach based on droplet microfluidics to analyze the effect of nearly all single mutations of the protease trypsin on its activity towards peptide substrates. The substrate specificity profile of this enzyme is extremely robust to single mutations, as we did not detect any activity towards new substrates in the single mutant library. Substrate specificity can only be fine-tuned towards the initial substrates by single mutations at a handful of residues in and out of the active site. These rare specificity fine-tuning residues are consistent with the analysis of pairwise residue coevolution in the protease family. Further, statistical modeling of pairwise residue coevolution allows engineering trypsin specificity towards new substrates with combinations of mutations. 

报告人简介：
Clement Nizak is a CNRS research director at Sorbonne University, Paris. After completing in 1999 his undergraduate studies in physics and chemistry at ESPCI, Paris, he received his PhD in biophysics in 2003 from Paris VII University. In 2003-2007, he was a postdoctoral associate at Rockefeller University, New York. His current research focuses on large-scale experiments to probe the sequence-function relationship in proteins for downstream statistical modeling, using antibodies and proteases as model systems. His past work includes the development of single-cell phenotyping and sequencing of immune repertoires based on droplet microfluidics, and an experimental physicist perspective on the unicellular/multicellular transition in social microbe populations.