Abstracts Biological Sciences

Aggregation of gluten proteins - from wheat seed biology to hydrogels : scientific modelling based primarily on Monte-Carlo and HPLC methods

by Joel Markgren

Gluten proteins are intrinsically disordered proteins that form extensive aggregated networks in wheat seeds, where they are stored as a nutrient source for the embryo. A modelling approach involving computational biology with Monte-Carlo algorithms and wet laboratory studies, including HPLC analysis, was applied to unravel the aggregational and hydrogelforming properties of the gluten proteins. Two of the gluten proteins, “αgliadin” and “low molecular weight glutenin subunits” (LMW-GS) were found to have similar size, folding of disordered, rigid and compact structures, elliptical shape and secondary structures of random coils and turns. Both proteins also share an evolutionarily conserved motif resulting in internal disulphide bonds, which were shown to be established through hydrophobic interactions, together with the inherent order of cysteines. In laboratory conditions and simulations, it was found that gliadins formed oligomers by hydrophobic interactions and cross-links by disulphide and lanthionine bonds at peptide sections in the C-terminal part of the protein. At the N-terminal part, the protein formed oligomers by liquid-liquid phase separation, polyproline II structures and β-sheets. Heat and alkaline treatment was shown to favour cross-linking by lanthionine, lysinoalanine and disulphide bonds among gliadins and increase their ability to absorb liquid. Thus the modelling approach successfully characterised the gluten proteins α-gliadin and LMW-GS, the mechanisms by which they form internal and external cross-links, how they merge into oligomers and how to increase their liquid absorption.