In
molecular biology
Molecular biology is a branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interactio ...
, the Bowman–Birk protease inhibitor family of proteins consists of
eukaryotic
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...
proteinase inhibitors, belonging to MEROPS inhibitor family I12, clan IF. They mainly
inhibit serine
Serine
(symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α- amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − ...
peptidases of the S1 family, but also inhibit S3 peptidases.
Members of this family have a duplicated structure and generally possess two distinct inhibitory sites. These inhibitors are primarily found in
plants
Plants are the eukaryotes that form the kingdom Plantae; they are predominantly photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars f ...
and in particular in the
seeds
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the ...
of
legume
Legumes are plants in the pea family Fabaceae (or Leguminosae), or the fruit or seeds of such plants. When used as a dry grain for human consumption, the seeds are also called pulses. Legumes are grown agriculturally, primarily for human consum ...
s, as well as in cereal grains.
In cereals, they exist in two forms, one of which is a duplication of the basic structure.
Proteins of the Bowman–Birk inhibitor family of serine proteinase inhibitors
interact with the
enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
s they inhibit via an exposed surface loop that adopts the canonical proteinase inhibitory conformation. The resulting noncovalent complex renders the proteinase inactive. This inhibition mechanism is common for the majority of serine proteinase inhibitor
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...
s, and many analogous examples are known. A particular feature of the Bowman–Birk inhibitor protein, however, is that the interacting loop is a particularly well-defined,
disulfide
In chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups.
In inorg ...
-linked, short
beta-sheet
The beta sheet (β-sheet, also β-pleated sheet) is a common structural motif, motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone chain, backbon ...
region.
See also
Kunitz STI protease inhibitor
References
External links
MEROPS family I12
{{DEFAULTSORT:Bowman-Birk protease inhibitor
Protein domains