Y-gliadins

Anderson, O.D., Hsia, C.C., Torres, V. 2001. Wheat y-gliadin genes Characterization of ten new sequences and further understanding of y-gliadin gene family structure. TheorAppl Genet 103 323-330. 

Morita, E., Yamamura, Y., Mihara, S., Kameyoshi, Y., Yamamoto, S. 2000. Food-dependent exercise-induced anaphylaxis A report of two cases and determination of wheat y-gliadin as the presumptive allergen. Br J Dermatol 143 1059-1063. 

The PDI-depleted microsomes can be reconstituted with the purihed enzyme by treating the microsomes with alkaline pH buffer containing high concentrations of PDI, reflecting the level of PDI in the microsomal lumen. After titrating the pH to 7.5 the microsomes are reisolated by centrifugation. When the y-gliadin mRNA was translated in the presence of PDI-reconstituted microsomes, the defect in disulhde bond formation observed with PDI-depleted microsomes was reversed (Fig. 6c). Control... 

Fig. 4. Schematic structure of y-gliadin. Modified from Kreis et al. (1985). Regions A, B, and C are found in other related cereal storage proteins. The disulphide pairing is inferred from the homology of the C-terminal domain to cereal seed inhibitions of amylase.

Fig. 5. Cell-free translation of -y-gliadin mRNA. The -y-gliadin niRNA was translated in the absence (lanes 1 and 5) or presence (lanes 2-4 and 6) of dog pancreas inicrosomes. Translation products were separated by SDS-PAGE under reducing conditions (lanes I -3, 5, and 6) and under nonreducing conditions (lane 4). Lanes 1 and 5 are products of translation in the absence of microsomal vesicles lanes 3,4, and 6 are products of translation in the presence of microsomal vesicles translation products of lanes 3 and 4 were treated with proteinase K translation products of lane 6 were treated with 1 (v/v) Friton X-100 and proteinase K.

The sulfur-rich prolamins are quantitatively the most abundant group in wheat, barley and rye, accounting for approximately 80-90% of total prolamin fractions. They include polymeric and monomeric components and consist of at two families in each species, the B- and y-hordeins of barley two types of y-secalin of rye and a, 3 and y-gliadins and LMW glutenin subunits of wheat. The sulfur-poor prolamins include C-hordeins of barley, (O-secalin of rye and co-gliadin of wheat. 

Figure 13.4 The major groups of wheat gluten proteins. The (o-gliadins and HMW subunits are defined as S-poor prolamins and HMW prolamins respectively. The a/P-gliadins, y-gliadins and LMW subunits are S-rich prolamins [12].

Figure 13.7 Schematic sequences of a typical a-gliadin, y-gliadin, LMW subunit of wheat, and a co-secalin of rye. The repeated sequences present in the gliadins, LMW subunits and (o-secalin are based on related motifs and are rich in proline and glutamine. The repeated sequences in the HMW subunits are not related to those present in the other proteins [12,21].

The HMW-GS account for about 5-10% of the total protein [27]. The LMW-GS most closely resemble y-gliadins in sequence and comprise about 20-30% of the total protein [28]. Three to six HMW-GS [29] and 15-20 different LMW-GS proteins are recognised in 1 and 2D gels of hexaploid wheat [30]. 

RP-HPLC is also an invaluable tool to estimate wheat quality. As already noted, this may be done by identifying genotypes [139]. RP-HPLC can also, however, detect specific proteins that serve as markers of quality. Bietz et al. [139] first identified durum y-gliadin RP-HPLC peaks that correlated with pasta quality and... 

In this way, the prolamines of wheat can be separated into C0-, a-, y-gliadins (Fig. 15.5), different varieties of wheat giving different patterns, e. g., the cultivars Clement and Maris Huntsman... 

Fig. 15.7). This chromatogram also contains the (05-, col, 2-, and y-gliadins, which are not separated during pre-fractionation because of varying solubilities (cf. 15.2.1.2). 

Fig. 15.5. RP-HPLC of the gliadin fractions of various wheat cultivars on Synchro Pac Ci8 (50 °C, aqueous 2-propanol/trifluoroacetic acid/acetonitrile 22-34 min co-gliadins, 33-51 min a-gliadins, 52-72 min y-gliadins according to Wieser et al., 1987)...

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