Abstract
Gluten protein crosslinking is a predetermined process where specific intra- and intermolecular disulfide bonds differ depending on the protein and cysteine motif. In this article, all-atom Monte Carlo simulations were used to understand the formation of disulfide bonds in gliadins and low molecular weight glutenin subunits (LMW-GS). The two intrinsically disordered proteins appeared to contain mostly turns and loops and showed “self-avoiding walk” behavior in water. Cysteine residues involved in intramolecular disulfide bonds were located next to hydrophobic peptide sections in the primary sequence. Hydrophobicity of neighboring peptide sections, synthesis chronology, and amino acid chain flexibility were identified as important factors in securing the specificity of intramolecular disulfide bonds formed directly after synthesis. The two LMW-GS cysteine residues that form intermolecular disulfide bonds were positioned next to peptide sections of lower hydrophobicity, and these cysteine residues are more exposed to the cytosolic conditions, which influence the crosslinking behavior. In addition, coarse-grained Monte Carlo simulations revealed that the protein folding is independent of ionic strength. The potential molecular behavior associated with disulfide bonds, as reported here, increases the biological understanding of seed storage protein function and provides opportunities to tailor their functional properties for different applications.
Highlights
The gluten protein complex is highly abundant in the wheat seed [1] and consists of storage proteins, which are known to form the largest protein networks in nature [2]
Based on the amino acid composition, the gliadins are further subdivided into three major classes, α-/β, γ, and ω-gliadins, whereas the glutenins are divided into low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits (GS)
Our models of gliadins and LMW‐GS are strikingly similar when it comes to secondary structure, size, and shape
Summary
The gluten protein complex is highly abundant in the wheat seed [1] and consists of storage proteins, which are known to form the largest protein networks in nature [2]. Similar types of proteins are found in other cereals and grasses (Poaceae) and are all genetically closely related and show high resemblance [3,4]. These proteins often share a high proline and glutamine content, amino acids lined in repetitive motifs, and cysteines (CYS) that form disulfide bonds that, in several cases, crosslink with other storage proteins [5]. Based on the amino acid composition, the gliadins are further subdivided into three major classes, α-/β-, γ-, and ω-gliadins, whereas the glutenins are divided into low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits (GS) Among these proteins, the gliadins and the LMW-GS have a similar evolutionary background; they share several features in their primary structure
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