BPTI/Kunitz family of serine protease inhibitors.
SMART accession number:SM00131
Description: Serine protease inhibitors. One member of the family is encoded by an alternatively-spliced form of Alzheimer's amyloid beta-protein.
Interpro abstract (IPR002223):

The majority of the sequences having this domain belong to the MEROPS inhibitor family I2, clan IB; the Kunitz/bovine pancreatic trypsin inhibitor family, they inhibit proteases of the S1 family [ (PUBMED:14705960) ] and are restricted to the metazoa with a single exception: Amsacta moorei entomopoxvirus. They are short (~50 residue) alpha/beta proteins with few secondary structures. The fold is constrained by 3 disulphide bonds. The type example for this family is aprotinin (bovine pancreatic trypsin inhibitor) [ (PUBMED:1714504) ] (or basic protease inhibitor), but the family includes numerous other members [ (PUBMED:1703675) (PUBMED:1593645) (PUBMED:8159751) (PUBMED:1304909) ], such as snake venom basic protease; mammalian inter-alpha-trypsin inhibitors; trypstatin, a rodent mast cell inhibitor of trypsin; a domain found in an alternatively-spliced form of Alzheimer's amyloid beta-protein; domains at the C-termini of the alpha(1) and alpha(3) chains of type VII and type VI collagens; and tissue factor pathway inhibitor precursor.

The pancreatic trypsin inhibitor (Kunitz) family [ (PUBMED:6996568) (PUBMED:1703675) (PUBMED:1593645) ] is one of the numerous families of serine proteinase inhibitors. The basic structure of such a type of inhibitor is shown in the following schematic representation:

| +--------+ |
| | **|******* |
| |

{------50 residues------}

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

GO function:serine-type endopeptidase inhibitor activity (GO:0004867)
Family alignment:
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There are 33749 KU domains in 16023 proteins in SMART's nrdb database.

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