Poster Presentation International Peptide Symposium 2023

Investigating the Biosynthesis of the Antimicrobial Peptide Lexapeptide. (#242)

Emily Grant-Mackie 1 2 , Margaret Brimble 1 , Paul Harris 2 , Ghader Bashiri 2
  1. University of Auckland, Auckland, AUCKLAND, New Zealand
  2. School of Biological Sciences, The University of Auckland, Auckland, NewZealand

Antimicrobial resistance is now one of the leading health concerns of the modern era, with many of our clinical antibiotics struggling to combat this global issue.1 This has led scientists to look to nature for new defences against this growing crisis. Lanthipeptides are an important sub-class of ribosomally synthesised and post-translationally modified peptides (RiPPs).2 Lexapeptide is a novel lanthipeptide discovered in 2016 and has potent antibacterial properties against Gram-positive bacteria.3 It contains many of the same structures found in other lanthipeptides including a (2S,6R)-lanthionine ring, 2,3-dehydroalanine and (Z)-2,3-dehydrobutyrine residues. Lexapeptide also contains some rarer structural moieties: an N-terminal (N,N)-dimethyl phenylalanine, a C-terminal (2-aminovinyl)-3-methyl-cysteine (AviMeCys) and a D-alanine.3 It is believed that these post translational modifications are what gives Lexapeptide its antibacterial properties, however there is limited methodology for these structures, particularly the AviMeCys motif. We hypothesise the natural Lexapeptide enzymes can help with the insertion of the AviMeCys. To investigate this, the unmodified linear peptide sequence (LxmA) needs to be synthesised. Attempts to synthesise LxmA using normal Fmoc solid phase synthesis were more difficult than anticipated, due to limited synthesis options enforced by the C-terminal cysteine. Hence a Dawson linker strategy was used to insert the cysteine after synthesis of the peptide to overcome these issues, by reacting it with an activated N-acyl-benzimidazolinone linker to cleave the full peptide from the resin and simultaneously insert the cysteine.4 Synthesis proved to be successful on model peptides with improved purity compared to previous attempts. An investigation took place where an unprotected threonine was converted to the Dhb on resin before the cysteine was added. These strategies will then be applied to prepare full length LxmA analogues and study the ability of the Lexapeptide enzymes to install the AviMeCys ring toward the total synthesis of Lexapeptide.

  1. Nolte, O. Antimicrobial Resistance in the 21st Century: A Multifaceted Challenge. Protein Pept. Lett. 2014, 21 (4), 330–335.
  2. Ongey, E. L.; Neubauer, P. Lanthipeptides: Chemical Synthesis versus in Vivo Biosynthesis as Tools for Pharmaceutical Production. Microb. Cell Factories 2016, 15 (1), 97.
  3. Xu, M.; Zhang, F.; Cheng, Z.; Bashiri, G.; Wang, J.; Hong, J.; Wang, Y.; Xu, L.; Chen, X.; Huang, S.-X.; Lin, S.; Deng, Z.; Tao, M. Functional Genome Mining Reveals a Class V Lanthipeptide Containing a D-Amino Acid Introduced by an F420 H2 -Dependent Reductase. Angew. Chem. Int. Ed Engl. 2020, 59 (41), 18029–18035.
  4. Arbour, C. A.; Kondasinghe, T. D.; Saraha, H. Y.; Vorlicek, T. L.; Stockdill, J. L. Epimerization-Free Access to C-Terminal Cysteine Peptide Acids, Carboxamides, Secondary Amides, and Esters via Complimentary Strategies. Chem. Sci. 2018, 9 (2), 350–355.