PROSITE documentation PDOC00253

Bowman-Birk serine protease inhibitors family signature

The Bowman-Birk inhibitor family [1] is one of the numerous families of serine proteinase inhibitors. As it can be seen in the schematic representation, they have a duplicated structure and generally possess two distinct inhibitory sites:

            +------------------------------------------------+
            |      +-----+       +-------+    +-----+        |
            |      |     |       |       |    |     |        |
          xxCCxxCxxCxx#xxCxxCxxxxCxxxCxxxCxxxxCxx#xxCxxCxxCxxCxx
             |  |           |********|****             |  |
             |  |           |        |                 |  |
             +--|-----------+        +-----------------+  |
                +-----------------------------------------+

            <-----------------70 residues-------------------->

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

These inhibitors are found in the seeds of all leguminous plants as well as in cereal grains. In cereals they exist in two forms, one of which is a duplication of the basic structure shown above [2]. The pattern we developed to pick up sequences belonging to this family of inhibitors is in the central part of the domain and includes four cysteines.