Proteinase inhibitor I7, squash (IPR000737)

Short name: Prot_inh_squash

Overlapping homologous superfamilies

Family relationships



The squash inhibitors form one of a number of serine proteinase inhibitor families. They belong to MEROPS inhibitor family I7, clan IE. They are generally annotated as either trypsin or elastase inhibitors (MEROPS peptidase family S1, IPR001254). The proteins, found exclusively in the seeds of the cucurbitaceae, e.g. Citrullus lanatus (watermelon), Cucumis sativus (cucumber), Momordica charantia (balsam pear), are approximately 30 residues in length and contain 6 Cys residues, which form 3 disulphide bonds [PMID: 2914611]. The inhibitors function by being taken up by a serine protease (such as trypsin), which cleaves the peptide bond between Arg/Lys and Ile residues in the N-terminal portion of the protein [PMID: 1731946, PMID: 2914611]. Structural studies have shown that the inhibitor has an ellipsoidal shape, and is largely composed of beta-turns [PMID: 2914611]. The fold and Cys connectivity of the proteins resembles that of potato carboxypeptidase A inhibitor [PMID: 1731946].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0004867 serine-type endopeptidase inhibitor activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns