This domain of is found in several C. elegans proteins. The domain is 30 amino acids long and rich in cysteine residues. There are 6 conserved cysteine positions in the domain that form three disulphide bridges. The domain is found in the potassium channel inhibitor ShK in sea anemone [1][2].

1: Solution structure of ShK toxin, a novel potassium channel inhibitor from a sea anemone. Tudor JE, Pallaghy PK, Pennington MW, Norton RS; Nat Struct Biol. 1996;3:317-320. PMID:8599755

2: Characterization of a potassium channel toxin from the Caribbean Sea anemone Stichodactyla helianthus. Castaneda O, Sotolongo V, Amor AM, Stocklin R, Anderson AJ, Harvey AL, Engstrom A, Wernstedt C, Karlsson E; Toxicon. 1995;33:603-613. PMID:7660365