Conformational studies of peptides corresponding to the coeliac-activating regions of wheat alpha-gliadin.
The structures of four peptides corresponding to parts of the coeliac-activating protein A-gliadin were studied by structure prediction and c.d. spectroscopy. Three of the peptides corresponded to parts of the coeliac-activating N-terminal region (residues 3-55, 3-19 and 39-45) and contained two tetrapeptide motifs common to all coeliac-active regions (Pro-Ser-Gln-Gln and Gln-Gln-Gln-Pro). The Pro-Ser-Gln-Gln sequence was also present in the fourth peptide, on the basis of the C-terminal part of the molecule (211-217). These studies showed that beta-reverse turns were the predominant structural feature in all peptides and were predominantly of type I/III in two of the N-terminal peptides and type II in the C-terminal peptide. These turns form when the peptide is dissolved in solvents of low dielectric constant (trifluoroethanol) and high dielectric constant (water and iso-osmotic saline), although their presence in the N-terminal peptides may be masked in the latter solvents due to equilibrium with a poly-L-proline II structure favoured at lower temperatures.
AFRC Institute of Arable Crops Research, Rothamsted Experimental Station, Harpenden, Herts., U.K.
A S
AS
Tatham
M N
MN
Marsh
H
H
Wieser
P R
PR
Shewry
D000595:Amino Acid Sequence; D000941:Antigens / Q000276:immunology; D002446:Celiac Disease / Q000276:immunology; D002942:Circular Dichroism; D005026:Ethylene Glycols; D005903:Gliadin / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology; D010940:Plant Proteins / Q000276:immunology; D011487:Protein Conformation; D012997:Solvents; D013329:Structure-Activity Relationship; D013696:Temperature; D014270:Trifluoroethanol
D000941:Antigens; D005026:Ethylene Glycols; D010446:Peptide Fragments; D010940:Plant Proteins; D012997:Solvents; D014270:Trifluoroethanol; D005903:Gliadin