Gliadins structure

Wieser, H. 1996. Relation between gliadin structure andcoeliac toxicity. ActaPaediatr 412(85 Suppl.) 3-9. 

This chapter has reviewed the application of ROA to studies of unfolded proteins, an area of much current interest central to fundamental protein science and also to practical problems in areas as diverse as medicine and food science. Because the many discrete structure-sensitive bands present in protein ROA spectra, the technique provides a fresh perspective on the structure and behavior of unfolded proteins, and of unfolded sequences in proteins such as A-gliadin and prions which contain distinct structured and unstructured domains. It also provides new insight into the complexity of order in molten globule and reduced protein states, and of the more mobile sequences in fully folded proteins such as /1-lactoglobulin. With the promise of commercial ROA instruments becoming available in the near future, ROA should find many applications in protein science. Since many gene sequences code for natively unfolded proteins in addition to those coding for proteins with well-defined tertiary folds, both of which are equally accessible to ROA studies, ROA should find wide application in structural proteomics. 

Despite different sequences and repetitive motives, all gliadins have the same secondary structure of loose spirals which are a balanced compromise between the p-spiral and poly-L-proline structure (polyproline helix II) (Parrot et al., 2002), the balance is dependent on temperature, type of solvent, and hydration level (Miles et al., 1991). Similar sequences can be found in other proteins, mainly animal proteins such as elastin and collagen, and they are responsible for particular biomechanical properties connected to reverse P-spirals or p-sheet structures (Tatham and Shewry, 2000). 

Anderson, O.D., Greene, F.C. 1997. The a-gliadin gene family. II. DNA and protein sequence variation, subfamily structure, and origins of pseudogenes. TheorAppl Genet 95 59-65. 

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. 

Popineau, Y. and Pineau, F. 1993. Emulsifying properties of wheat gliadins and gliadin peptides In Food Proteins. Structure and Functionality (K.D. Schwenke and R. Mothes eds), pp. 290-296. VCH, Weinheim. 

Gliadin Gliadin, a glycoprotein derived from gluten, is extracted from wheat and separated by capillary electrophoresis [34,35]. Gliadin is classified as co-5, co-1,2, a, and y- type based on its structure and electrophoretic mobility [36].The glycoprotein is water insoluble due to the presence of interpolypeptide disulfide bonds and hydrophobic interactions. A limitation on the use of gliadins is that patient sensitivity causes an autoimmune disorder called celiac disease. 

From the unique amino acid composition of the gliadin proteins, one would expect a structure that is quite different from globular proteins. However, optical rotation studies have shown that the gliadin proteins possess compact tertiary structures similar to those of globular proteins (4,5). 

Figure 2. Schematic of conformational structure and aggregate state of A-gliadin under various conditions (9)...

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.

Other lipophilic molecules can be incorporated into the lipid bilayer of the cubic monoolein-water phase, for example gliadin. An electron micrograph showing the Cp structure of a lipid-protein-water phase is shown in Fig. 5.3. The body-centred structure characteristic of the P-surface is evident from the displacement of adjacent fracture planes. 

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