Structural determinants of the binding of gliadin fragments to human peripheral blood lymphocytes

A series of alpha-gliadin fragments, structurally related to alpha-gliadin-(43-49), were synthesized. The effect of these fragments and beta-casomorphin and naloxone on the steady-state binding of [125I]-alpha-gliadin-(43-49) to human peripheral blood lymphocytes was investigated. In an attempt to correlate the binding data with the conformation of the peptides, their circular dichroism spectra were measured in both trifluorethanol and aqueous solution. It was found that there is a striking correlation between the results of the binding studies and the chiroptical properties of the gliadin fragments. The presence of N-terminal tyrosine and the tendency of the peptides to adopt periodic, 310 helix-like secondary structure appear to be crucial for the binding to human peripheral blood lymphocytes.