Circular dichroism and electron microscopy studies in vitro of 33-mer gliadin peptide revealed secondary structure transition and supramolecular organization

HERRERA. M.G; ZAMARREÑO F.; COSTABEL. M.; RITACCO. H.; HÜTTEN. A.; SEWALD. N.; DODERO.V.I

BIOPOLYMERS

JOHN WILEY & SONS INC

Lugar: New York; Año: 2013

0006-3525

Gliadin, a protein present in wheat, rye and barley, undergoes incomplete enzymatic degradation during digestion, producing an immunogenic 33-mer peptide, LQLQPF(PQPQLPY)3PQPQPF. The special features of 33-mer that provoke a break in its tolerance leading to gliadin sensitivity and celiac disease remains elusive. Herein it is reported that 33-mer gliadin peptide was not only able to fold into PPII secondary structure, but also depending on concentration conformational transition and self-assembly proceeded under aqueous condition, pH 7.0. A 33-mer dimer is presented as one initial possible step in the self-assembly process obtained by partial electrostatics charge distribution calculation and molecular dynamics. In addition, electron microscopy experiments revealed supramolecular organization of 33-mer into colloidal nanospheres. In the presence of 1 mM sodium citrate, 1mM sodium borate, 1 mM sodium phosphate buffer, 15 mM NaCl the nanospheres were stabilized, while in water a linear organization and formation of fibrils were observed. It is hypothesized that the self-assembly process could be the result of the combination of hydrophobic effect, intramolecular hydrogen bonding and electrostatic complementarity due to 33-mer high content of proline and glutamine amino acids and its calculated non-ionic amphiphilic character. Although, performed in vitro, our experiments have revealed new features of the 33-mer gliadin peptide that could represent an important and unprecedented event in the early stage of 33-mer interaction with the gut mucosa prior to onset of inflammation. Moreover, these findings may open new perspectives for the understanding and treatment of gliadin intolerance disorders.