Mapping Coeliac Toxic Motifs in the Prolamin Seed Storage Proteins of Barley, Rye, and Oats Using a Curated Sequence Database

Abstract

Wheat gluten, and related prolamin proteins in rye, barley and oats cause the immune-mediated gluten intolerance syndrome, coeliac disease. Foods labelled as gluten-free which can be safely consumed by coeliac patients, must not contain gluten above a level of 20 mg/Kg. Current immunoassay methods for detection of gluten can give conflicting results and may underestimate levels of gluten in foods. Mass spectrometry methods have great potential as an orthogonal method, but require curated protein sequence databases to support method development. The GluPro database has been updated to include avenin-like sequences from bread wheat (n = 685; GluPro v1.1) and genes from the sequenced wheat genome (n = 699; GluPro v 1.2) and Triticum turgidum ssp durum (n = 210; GluPro v 2.1). Companion databases have been developed for prolamin sequences from barley (n = 64; GluPro v 3.0), rye (n = 41; GluPro v 4.0), and oats (n = 27; GluPro v 5.0) and combined to provide a complete cereal prolamin database, GluPro v 6.1 comprising 1,041 sequences. Analysis of the coeliac toxic motifs in the curated sequences showed that they were absent from the minor avenin-like proteins in bread and durum wheat and barley, unlike the related avenin proteins from oats. A comparison of prolamin proteins from the different cereal species also showed α-and γ-gliadins in bread and durum wheat, and the sulphur poor prolamins in all cereals had the highest density of coeliac toxic motifs. Analysis of ion-mobility mass spectrometry data for bread wheat (cvs Chinese Spring and Hereward) showed an increased number of identifications when using the GluPro v1.0, 1.1 and 1.2 databases compared to the limited number of verified sequences bread wheat sequences in reviewed UniProt. This family of databases will provide a basis for proteomic profiling of gluten proteins from all the gluten containing cereals and support identification of specific peptide markers for use in development of new methods for gluten quantitation based on coeliac toxic motifs found in all relevant cereal species.

Tritordeum as an Innovative Alternative to Wheat: A Comparative Digestion Study on Bread

“…The availability of well annotated and curated protein sequence databases is essential for inferring relevant information from mass spectrometry data. The analysis of cereal seed storage proteins is challenging because of the natural polymorphism, with a high number of protein isoforms differing by point mutations, and the homology across cvs and species [26]. Tritordeum, being a novel crop, lacks a protein database.…”

“…These misidentifications may be due to the bioinformatic protein inferring process, that would only list peptides with 100% identity. Wheat proteins are characterized by high polymorphism and the presence of several protein sequences differing by few amino acids [26]. The protein assignment informs about the presence of a protein family rather than a specific protein, especially for gluten proteins.…”

Multiple Antioxidative and Bioactive Molecules of Oats (Avena sativa L.) in Human Health

“…Compared to other grains, proteins in oats are superior in quantity and quality, especially for humans and non-ruminants, based on the composition of essential amino acids. Seed storage proteins of grains are divided into globulins, which are soluble in salt, and prolamins, which are soluble in alcohol [ 16 , 25 ]. Among essential amino acids, lysine, which plays a crucial role in protein biosynthesis, is particularly important as this amino acid cannot be synthesized and must be obtained from the external environment in mammals [ 26 ].…”

Gluten‐free and prebiotic oat bread: Optimization formulation by transglutaminase improvement dough structure

“…It can cause small intestinal mucosa structural change, resulting in nutritional absorption impaired, diarrhea, and weight loss (Rondanelli et al, 2019). So far, the remedy for CD patients is a gluten-free diet (GFD) (Ruiz-Carnicer et al, 2020).The food with gluten content less than 20 mg/kg can be safely consumed for CD patients (Daly et al, 2020). However, many glutenfree foods are low in fiber, vitamin, and high in fat, sugar, which can easily lead to constipation, obesity, and cardiovascular diseases…”

“…The food with gluten content less than 20 mg/kg can be safely consumed for CD patients (Daly et al, 2020). However, many glutenfree foods are low in fiber, vitamin, and high in fat, sugar, which can easily lead to constipation, obesity, and cardiovascular diseases…”