Insect cuticle is composed of proteins and chitin. The cuticular proteins seem
to be specific to the type of cuticle (flexible or stiff) that occur at stages
of the insect development. The proteins found in the flexible cuticle of larva
and pupa of different insects share a conserved C-terminal section ; such a
region is also found in the soft endocuticle of adults insects  as well as
in other cuticular proteins including in arachnids . This conserved motif
of 35-36 amino acids is known as the R&R consensus since it was first
recognized by Rebers and Riddiford. N-terminal to the consensus is a region of
hydrophilic amino acids. The two regions together have been called the
extended R&R consensus and form an about 70 amino acids chitin-binding domain
The R&R chitin-binding domain has been proposed to constitute antiparallel
β-pleaated sheets .
Some proteins known to contain a R&R chitin-binding domain are listed below:
Talbo G., Hoejrup P., Rahbek-Nielsen H., Andersen S.O., Roepstorff P.
Determination of the covalent structure of an N- and C-terminally blocked glycoprotein from endocuticle of Locusta migratoria. Combined use of plasma desorption mass spectrometry and Edman degradation to study post-translationally modified proteins.
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