Pyrrole-Mediated Peptide Cyclization Identified through Genetically Reprogrammed Peptide Synthesis.

Area of Science:

• Chemical Biology
• Organic Chemistry
• Biochemistry

Background:

• Peptide modification and cyclization are crucial for developing novel therapeutics and research tools.
• Existing methods for peptide constraining often require complex multi-step syntheses or specific protecting groups.

Purpose of the Study:

• To discover a new methodology for peptide constraining using a furan-based crosslinking strategy.
• To explore the potential of nucleophilic amino acid side chains attacking an oxidized furylalanine residue for cyclization.

Main Methods:

• Flexible in vitro translation (FIT) was employed for initial screening of template peptides containing furylalanine and various nucleophilic residues.
• Selective furan oxidation was induced using N-bromosuccinimide (NBS), followed by MALDI analysis.
• Solid-phase peptide synthesis (SPPS) was utilized for larger-scale synthesis and characterization, including NMR spectroscopy.

Main Results:

• Lysine and Serine were identified as promising nucleophilic residues for cyclization with oxidized furylalanine.
• A one-pot oxidation and reduction reaction with a lysine-containing peptide yielded a cyclic peptide with a pyrrole moiety.
• The study provides structural evidence via NMR and explores the generality of this novel cyclization approach.

Conclusions:

• A new, efficient method for peptide cyclization has been established, utilizing the reaction between lysine and oxidized furylalanine.
• This methodology expands the utility of furan-based chemistry for peptide labeling and crosslinking.
• The generated pyrrole-containing cyclic peptides offer new structural motifs for diverse applications in chemical biology.