Investigations into the biosynthesis and mode of action of the antimicrobial peptides epilancin 15x and sublancin

Wu, Chunyu

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https://hdl.handle.net/2142/115898 Copy

Description

Title

Investigations into the biosynthesis and mode of action of the antimicrobial peptides epilancin 15x and sublancin

Author(s)

Wu, Chunyu

Issue Date

2022-07-11

Director of Research (if dissertation) or Advisor (if thesis)

van der Donk, Wilfred A

Doctoral Committee Chair(s)

van der Donk, Wilfred A

Committee Member(s)

• Nair, Satish K
• Tajkhorshid, Emad
• Kehl-Fie, Thomas E

Department of Study

Biochemistry

Discipline

Biochemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Peptides, RiPPs, mode of action, bacteria, biosynthesis, antibiotics, lanthipeptides, glycocins

Abstract

Antimicrobial resistance is a present-day global threat. A rising concern for antimicrobial resistance is the limited number of targets in bacteria affected by our current pool of antibiotics. Over two hundred approved antibacterial drugs target a small number of bacterial processes, including DNA replication, RNA synthesis, protein synthesis, folate synthesis, and cell wall biosynthesis. However, an increasing number of bacterial strains have overcome the action of these antibiotics by developing drug-resistant mutations in the original targets or developing alternative resistance mechanisms. To combat this issue, the discovery of new antibacterial agents that function through novel modes of action is important. Ribosomally-synthesized and post-translationally modified peptide (RiPP) natural products are a rapidly expanding class of compounds, many of which have antimicrobial activity. The molecular target of the majority of RiPPs is currently unknown. The studies described herein focus on the mode of action and biosynthesis of two RiPPs, sublancin 168 and epilancin 15X. Sublancin 168 is one of several characterized members of the glycocin family of RiPPs and contains an unusual S-linked glucose moiety. This unusual post-translational modification leads to a unique antibacterial mode of action. In chapter 2, the mode of action of sublancin was investigated, suggesting that the antimicrobial activity of sublancin is dependent on the phosphoenolpyruvate-phosphotransferase system (PTS). Epilancin 15X is a member of the lanthipeptide family of RiPPs and contains an unusual N-terminal lactate group and eight positively charged amino acids. To understand the correlation between its structure and bioactivity, a novel lanthipeptide heterologous expression system was built, and structure-activity relationship (SAR) studies were performed as described in chapter 3. The new system to heterologously produce class I lanthipeptides in Escherichia coli through co-expressing the producer’s glutamyl-tRNA synthetase (GluRS) and glutamyl-tRNAGlu pair in the vector pEVOL yielded fruitful production of lanthipeptides from both Gram-positive and Gram-negative bacteria. Finally, the mode of action of epilancin 15X was studied in chapter 4, which identified its pore-formation ability through interacting with negatively charged lipids on bacterial membranes.

Graduation Semester

2022-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Chunyu Wu

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