Argos is a natural secreted antagonist of EGFR signalling which functions by binding growth factor ligands that activate EGFR by forming a clamp like structure using three disulphide-bonded beta-sheet domains [1].

1: Structural basis for EGFR ligand sequestration by Argos. Klein DE, Stayrook SE, Shi F, Narayan K, Lemmon MA; Nature. 2008;453:1271-1275. PMID:18500331