PROSITE documentation PDOC00258

Squash family of serine protease inhibitors signature

The squash family of serine protease inhibitor [1] is one of the numerous families of serine proteinase inhibitors. The proteins belonging to this family are found in the seeds of cucurbitaceae plants (cucumber, squash, bitter gourd, etc.). The basic structure of such a type of inhibitor is shown in the following schematic representation:

                          +----------------+
                          |                |
                          *****************|**
                        xxCx#xxxxCxxxxxCxxxCxCxxxxxCx
                                 |     |     |     |
                                 |     +-----|-----+
                                 +-----------+

                        <--------30 residues-------->

'C': conserved cysteine involved in a disulfide bond.
'#': active site residue.
'*': position of the pattern.

The pattern we have used to detect this family of proteins spans the major part of the sequence and includes five of the six cysteines involved in disulfide bonds.