Applications of Unnatural Amino Acid Mutagenesis for Biocatalysis and Molecular Recognition Public Deposited

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Last Modified
  • March 20, 2019
Creator
  • Baril, Stefanie
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • Proteins are diverse biopolymers constructed from 20 canonical amino acids, affording innumerable amino acid combinations. This combinatorial diversity allows for a variety of essential cellular functions ranging from enzyme catalysis, molecular recognition, signal transduction, structure, and beyond. Although nature has successfully evolved proteins for numerous purposes, protein function is limited by the restricted chemical functionality of the canonical amino acids. For example, natural amino acids include only a handful of residues capable of participating directly in catalysis. In addition, amino acid mutations rarely allow for fine-tuned changes to the amino acid side chain. Although information may be discovered from natural amino acid mutations, it is often difficult to determine how protein function would change with more subtle modulations of the chemical properties of the amino acid. With the introduction of in vivo unnatural amino acid (UAA) mutagenesis, amino acid sidechains may be expanded into previously unavailable chemical functionalities. The purpose of this dissertation is to expand the applications of unnatural amino acid mutagenesis into two diverse fields: 1) biophysical investigations of molecular recognition motifs that exploit cation-π interactions, and 2) biocatalysis using cofactor-like UAAs. For our biophysical studies, we examined cation-π interactions between epigenetic reader proteins and their cationic ligands. UAAs with different electron-withdrawing or –donating groups were incorporated into the binding site, thereby tuning the electronics of the cation-π interaction. This methodology was successfully applied to Heterochromatin Protein 1, and we have engineered a new expression system to next study CBX5 and CBX7, which are implicated in multiple cancers. For biocatalysis, we have made progress towards genetically encoding a thiamine-like unnatural amino acid. Thiamine, a potent N-heterocyclic carbene cofactor, is required for cell metabolism in all domains of life. By incorporating a thiamine-like UAA in vivo, we are one step closer to transforming any binding pocket into a powerful N-heterocyclic carbene-containing enzyme as well as conferring active site stereoselectivity to existing N-heterocyclic carbene small molecule catalysts. It is our hope that our approaches will help the field of unnatural amino acid mutagenesis expand the tools available to protein chemists studying the innumerable proteins in our world.
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  • In Copyright
Advisor
  • Redinbo, Matthew R.
  • Kuhlman, Brian
  • Waters, Marcey
  • Pielak, Gary J.
  • Brustad, Eric
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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