CLIP is a regulatory domain which controls the proteinase action of various proteins of the trypsin family, e.g. easter and pap2. The CLIP domain remains linked to the protease domain after cleavage of a conserved residue which retains the protein in zymogen form. It is named CLIP because it can be drawn in the shape of a paper clip. It has many disulphide bonds and highly conserved cysteine residues, and so it folds extensively. [1] [2]

1: Dominant and recessive alleles of the Drosophila easter gene are point mutations at conserved sites in the serine protease catalytic domain. Jin YS, Anderson KV; Cell. 1990;60:873-881. PMID:2107028

2: The clip-domain family of serine proteinases in arthropods. Jiang H, Kanost MR; Insect Biochem Mol Biol. 2000;30:95-105. PMID:10696585