Biosynthesis of the Polycyclic Antimicrobial Peptides Lacticin 481, Haloduracin, and Cinnamycin
Cooper, Lisa E.
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https://hdl.handle.net/2142/72345
Description
Title
Biosynthesis of the Polycyclic Antimicrobial Peptides Lacticin 481, Haloduracin, and Cinnamycin
Author(s)
Cooper, Lisa E.
Issue Date
2009
Doctoral Committee Chair(s)
van der Donk, Wilfred A.
Department of Study
Biochemistry
Discipline
Biochemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Abstract
Lantibiotics are bacterial-derived polycyclic antimicrobial peptides. They are genetically encoded and ribosomally synthesized as precursor peptides containing a structural region that undergoes post-translational modification and a leader sequence that is not modified. Specific serine and threonine residues in the pre-lantibiotic structural region are dehydrated to dehydroalanine (Dha) and dehydrobutyrine (Dhb), respectively, and subsequently cyclized through intramolecular addition of cysteine thiol groups to these unsaturated amino acids. This process results in the formation of lanthionine (Lan; from Dha) and methyllanthionine (MeLan; from Dhb) rings. Removal of the leader peptide yields the mature biologically active compound. Class I lantibiotics are biosynthesized by a LanB dehydratase and a LanC cyclase while class II lantibiotics are generated by one bifunctional LanM enzyme. A previously developed in vitro production system for lacticin 481 was utilized in this study to investigate the molecular recognition elements involved in substrate binding for the lacticin 481 synthetase LctM. It was found that LctM could successfully process a series of substrate analogs, indicating that lantibiotics show promise for engineering novel therapeutic peptides. Using a bioinformatic approach, the two-peptide lantibiotic haloduracin was discovered and the activities of the haloduracin synthetases (HalM1 and HalM2) were reconstituted in vitro. Site-directed mutagenesis of the two precursor peptides HalA1 and HalA2 was employed to generate substrate analogs that were used in structure-activity relationship studies. Efforts toward the in vitro biosynthesis of the lantibiotic cinnamycin have been initiated, resulting in the successful incorporation of three thioether rings by CinM and an unusual hydroxylated aspartic acid residue by CinX.
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