Pyrrhocoricin is a 20-residue long antimicrobial peptide of the firebug Pyrrhocoris apterus.

The peptide is proline-rich with proline-arginine repeats, as well a critical threonine residue, which is required for activity through O-glycosylation.

Like the antimicrobial peptides drosocin and abaecin, pyrrhocoricin binds to the bacterial protein DnaK, inhibiting cell machinery and replication.

[4] Proline-rich peptides like Pyrrhocoricin can also bind to microbe ribosomes, preventing protein translation.

[5] In the absence of pore-forming peptides, pyrrhocoricin is taken into the bacteria by the action of bacterial uptake permeases.