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Title:Studies on the mechanism of action of the antimicrobial S-linked glycopeptide sublancin
Author(s):Garcia De Gonzalo, Chantal V
Director of Research:van der Donk, Wilfred A
Doctoral Committee Chair(s):van der Donk, Wilfred A
Doctoral Committee Member(s):Hergenrother, Paul J; Nair, Satish K; Mitchell, Douglas A
Department / Program:Chemistry
Discipline:Chemistry
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Glycocin
Ribosomally synthesized and post-translationally modified peptide (RiPP)
Antimicrobial
S-Linked
Abstract:Infectious diseases are a continuing threat to human health. In particular, the rapid development of bacterial antibiotic resistance not only decreases the effectiveness of known antibiotics, but also increases the need for the ongoing discovery of novel drugs. Since the discovery of penicillin, natural products have become a great source of templates for the development of new antibiotics. Derivatization of known drugs is one approach commonly used to combat rapidly evolving bacterial strains. However, the mechanisms of actions of derivatized drugs are more often than not very similar to the parent compound, making it difficult to develop drugs with new and unique modes of action by generating analogs. Ribosomally synthesized and post-translationally modified peptide (RiPP) natural products are a rapidly expanding class of compounds with antimicrobial activity. Sublancin is one of five members of the glycocin family of RiPPs, and contains an unusual S-linked glycosylation. This unprecedented post-translational modification, as well as its increased stability, when compared to known RiPP antimicrobials, suggests a unique antibacterial mode of action. In an effort to understand the remarkable stability of sublancin, the three-dimensional NMR structure was solved, as described in chapter 2, revealing that hydrophobic interactions as well as hydrogen bonding are responsible for the stable and well-structured peptide. Unlike better-understood natural products, the molecular target of sublancin is currently unknown. In order to further understand how sublancin exerts its activity against bacteria, a number of sublancin analogues were made. These analogues were prepared either by heterologous expression followed by in vitro modification, as well as by solid phase peptide synthesis. The antimicrobial activity of all analogues was then assessed against sensitive bacteria and sublancin-resistant mutant strains. While sublancin exhibits sub-micromolar activity against Gram-positive bacteria, its molecular target is currently unknown. Chapter 3 describes studies focused on understanding sublancin’s mode of action. In chapter 4 we performed super resolution microscopy and determined that sublancin localizes to the cell membrane. Furthermore, the mechanism of action of the S-glycosyltransferase SunS, the enzyme responsible for installing an S-linked sugar onto sublancin, was studied in chapter 5, which provided insights into its enzymatic mechanism. The understanding of the biosynthesis of these unique peptides can aid in the bioengineering of other, more potent complex molecules.
Issue Date:2015-10-12
Type:Thesis
URI:http://hdl.handle.net/2142/89179
Rights Information:Copyright 2015 Chantal V. Garcia De Gonzalo
Date Available in IDEALS:2016-03-02
Date Deposited:2015-12


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