Microcin J25 (MccJ25) is a ribosomally-synthesized peptide isolated from Escherichia coli that exhibits antimicrobial activities against strains of Salmonella, E. coli, and Shigella. The structure of this 21-aa peptide is highly resistant to proteases, and thermal and chemical denaturation due to its unusual threaded lasso topology. The N-terminal residues form a macrocyclic 8-residue �ring� followed by a C-terminal �tail� that is fed through the ring and locked in by two bulky residues positioned on both sides of the ring. We screened saturation mutagenesis libraries targeted to the ring and tail hairpin portions of MccJ25. We found that multiple amino acid substitutions in the tail of MccJ25 were well-tolerated for biosynthesis and antimicrobial activity, but mutagenesis of the ring likely disrupts the transport of the peptide variants into the cytoplasm and was detrimental to the antimicrobial function of MccJ25. As the tail hairpin region of MccJ25 is highly programmable, we built novel functions into the peptide, demonstrating its potential use as a hyperstable scaffold for peptide display.

Lasso peptide microcin J25 as a scaffold for peptide display

243rd National Meeting (2012)

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