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Many plants respond to pathogenic attack by producing defense proteins that
are capable of reversible binding to chitin, an N-acetylglucosamine
polysaccharide present in the cell wall of fungi and the exoskeleton of
insects. Most of these chitin-binding proteins include a common structural
motif of 30 to 43 residues organized around a conserved four-disulfide core,
known as the chitin-binding domain type-1 . The topological arrangement of
the four disulfide bonds is shown in the following figure:
'C': conserved cysteine involved in a disulfide bond.
'*': position of the pattern.
The structure of several chitin-binding domain type-1 have been solved, (see
for example <PDB:1HEV>) . The chitin-binding site is localized in a
β-hairpin loop formed by the second disulfide bridge. Conserved serine and
aromatic residues associated with the hairpin-loop are essential for the
chitin-binding activity . The chitin-binding domain type-1 displays some
structural similarities with the chitin-binding domain type-2 (see
Some of the proteins containing a chitin-binding domain type-1 are listed
A number of non-leguminous plant lectins. The best characterized of these
lectins are the three highly homologous wheat germ agglutinins (WGA-1, 2
and 3). WGA is an N-acetylglucosamine/N-acetylneuraminic acid binding
lectin which structurally consists of a fourfold repetition of the 43 amino
acid domain. The same type of structure is found in a barley root-specific
lectin as well as a rice lectin.
Plants endochitinases (EC 18.104.22.168) from class IA (see <PDOC00620>).
Endochitinases are enzymes that catalyze the hydrolysis of the β-1,4
linkages of N-acetyl glucosamine polymers of chitin. Plant chitinases
function as a defense against chitin containing fungal pathogens. Class IA
chitinases generally contain one copy of the chitin-binding domain at their
N-terminal extremity. An exception is agglutinin/chitinase  from the
stinging nettle Urtica dioica which contains two copies of the domain.
Hevein, a wound-induced protein found in the latex of rubber trees.
Win1 and win2, two wound-induced proteins from potato.
Kluyveromyces lactis killer toxin α subunit . The toxin encoded by
the linear plasmid pGKL1 is composed of three subunits: α, β, and
γ. The γ subunit harbors toxin activity and inhibits growth of
sensitive yeast strains in the G1 phase of the cell cycle; the α
subunit, which is proteolytically processed from a larger precursor that
also contains the β subunit, is a chitinase (see <PDOC00839>).
The profile we developed covers the whole domain.
Hevein is a strong allergen which is implied in the allergy to natural
rubber latex (NRL). NLR can be associated to hypersensitivity to some
plant-derived foods (latex-fruit syndrome). An increasing number of plant
sources, such as avocado, banana, chestnut, kiwi, peach, tomato, potato and
bell pepper, have been associated with this syndrome. Several papers [6,7]
have shown that allergen cross-reactivity is due to IgE antibodies that
recognize structurally similar epitopes on different proteins that are
closely related. One of these family is plant defence proteins class I
chitinase containing a type-1 chitin-binding domain.
December 2004 / Pattern and text revised.
PROSITE methods (with tools and information) covered by this documentation:
Wright H.T., Sandrasegaram G., Wright C.S.
Evolution of a family of N-acetylglucosamine binding proteins containing the disulfide-rich domain of wheat germ agglutinin.
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