Date of Award
2022
Document Type
Masters Thesis
Degree Name
M.S.
Organizational Unit
College of Natural Science and Mathematics, Chemistry and Biochemistry
First Advisor
John A. Latham
Second Advisor
Scott Nichols
Third Advisor
Martin Margittai
Fourth Advisor
Michelle K. Knowles
Keywords
Bioinformatics, Radical-S-adenosylmethionine enzyme, Ribosomally synthesized and posttranslationally modified peptide, Sequence similarity network, TIG biosynthesis
Abstract
Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a large class of natural products with significant human health implications. RiPPs are synthesized from a genetically encoded precursor peptide that undergoes significant modifications by maturing enzymes, or maturases. Recently, radical-S-adenosylmethionine (rSAM) enzymes have emerged as an important family of RiPP maturases. rSAM enzymes have been shown to install ether, thioether, and carbon-carbon bonds on the precursor peptide. These modifications usually define the backbone structure of the mature RiPP. This thesis describes the characterization of a novel RiPP modification catalyzed by the radical S-adenosylmethionine enzyme TigE. TigE belongs to the TIG biosynthetic gene cluster (BGC), which is encoded by tigABCDEF, found in the bacterium Paramaledivibacter caminithermalis. The TIG precursor peptide, TigB, is comprised of a repeating TIGSVSG motif. Using a variety of chromatography, mass spectrometry, isotopic labeling, and NMR spectroscopy techniques, we show that TigE catalyzes the formation of C-C bond between the γ-carbons on TigB isoleucine residues (Ile), forming a methyl-cyclopropyl glycine (mCPG). Using crystallography and site-directed mutagenesis, we also revealed that the TigE residue Tyr339 is critical for both the coordination of iron-sulfur clusters and chemistry and could be used as a biomarker for the discovery of other cyclopropyl synthases. This novel RiPP modification provided a reaction scope of radical S-adenosylmethionine enzymes.
Publication Statement
Copyright is held by the author. User is responsible for all copyright compliance.
Rights Holder
Yi Lien
Provenance
Received from ProQuest
File Format
application/pdf
Language
en
File Size
65 pgs
Recommended Citation
Lien, Yi, "Characterization of Cyclopropyl Synthases Involved in the Maturation of Ribosomally Synthesized and Posttranslationally Modified Peptides" (2022). Electronic Theses and Dissertations. 2129.
https://digitalcommons.du.edu/etd/2129
Copyright date
2022
Discipline
Biochemistry, Chemistry