The use of extended amino acid motifs for focussing on toxic peptides in coeliac disease.

Cereal prolamins of wheat, rye and barley are the major proteins that have been implicated in toxicity in patients with coeliac disease. The gliadins of wheat are the best characterised with the identification of toxic peptides from rye and barley not as well advanced. This study has employed extended motifs, based on the known toxic motifs are derived from the sequence of A-gliadin, to search protein databases for matches with coeliac-toxic cereals. The results obtained have provided pointers to specific regions in rye and barley prolamins, which have received little attention in in vitro and in vivo studies of toxicity in coeliac disease. The results obtained in this study indicate that the size of the extended motif is critical when searching for coeliac-toxic cereals using protein databases. Extended motifs that are common to all three coeliac-toxic cereals and found in active wheat gliadin peptides are QQPYP, PQQPY and QQQPFP.