Comparative study of wheat low-molecular-weight glutenin and α-gliadin trafficking in tobacco cells.

KEY MESSAGE : Wheat low-molecular-weight-glutenin and α-gliadin were accumulated in the endoplasmic reticulum and formed protein body-like structures in tobacco cells, with the participation of BiP chaperone. Possible interactions between these prolamins were investigated. Wheat prolamins are the major proteins that accumulate in endosperm cells and are largely responsible for the unique biochemical properties of wheat products.

Dynamic trafficking of wheat γ-gliadin and of its structural domains in tobacco cells, studied with fluorescent protein fusions.

Prolamins, the main storage proteins of wheat seeds, are synthesized and retained in the endoplasmic reticulum (ER) of the endosperm cells, where they accumulate in protein bodies (PBs) and are then exported to the storage vacuole. The mechanisms leading to these events are unresolved. To investigate this unconventional trafficking pathway, wheat γ-gliadin and its isolated repeated N-terminal and cysteine-rich C-terminal domains were fused to fluorescent proteins and expressed in tobacco leaf epidermal cells.

Structure and morphology of wheat gluten films: from polymeric protein aggregates toward superstructure arrangements.

Evaluation of structure and morphology of extruded wheat gluten (WG) films showed WG protein assemblies elucidated on a range of length scales from nano (4.4 Å and 9 to 10 Å, up to 70 Å) to micro (10 μm). The presence of NaOH in WG films induced a tetragonal structure with unit cell parameters, a = 51.

Expression of a new chimeric protein with a highly repeated sequence in tobacco cells.

In wheat, the high-molecular weight (HMW) glutenin subunits are known to contribute to gluten viscoelasticity, and show some similarities to elastomeric animal proteins as elastin. When combining the sequence of a glutenin with that of elastin is a way to create new chimeric functional proteins, which could be expressed in plants. The sequence of a glutenin subunit was modified by the insertion of several hydrophobic and elastic motifs derived from elastin (elastin-like peptide, ELP) into the hydrophilic repetitive domain of the glutenin subunit to create a triblock protein, the objective being to improve the mechanical (elastomeric) properties of this wheat storage protein.

Exploring the interactions of gliadins with model membranes: effect of confined geometry and interfaces.

Mechanisms leading to the assembly of wheat storage proteins into proteins bodies within the endoplasmic reticulum (ER) of endosperm cells are unresolved today. In this work, physical chemistry parameters which could be involved in these processes were explored. To model the confined environment of proteins within the ER, the dynamic behavior of gamma-gliadins inserted inside lyotropic lamellar phases was studied using FRAP experiments.

Structure and orientation changes of omega- and gamma-gliadins at the air-water interface: a PM-IRRAS spectroscopy and Brewster angle microscopy study.

Microscopic and molecular structures of omega- and gamma-gliadin monolayers at the air-water interface were studied under compression by three complementary techniques: compression isotherms, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). For high molecular areas, gliadin films are homogeneous, and a flat orientation of secondary structures relative to the interface is observed. With increasing compression, the nature and orientation of secondary structures changed to minimize the interfacial area.

Influence of the allelic variants encoded at the Gli-B1 locus, responsible for a major allergen of wheat, on IgE reactivity for patients suffering from food allergy to wheat.

Wheat presents an important genetic diversity that could be useful to look for cultivars with reduced allergencity. omega5-Gliadins have been described as major allergens for wheat allergic patients suffering from wheat-dependent exercise-induced anaphylaxis (WDEIA) and some cases of chronic urticaria (U). Our objective was to study the influence of genetic variability at the Gli-B1 locus encoding for omega5-gliadins on the reactivity of IgE antibodies from these patients.

Characterisation and foaming properties of hydrolysates derived from rapeseed isolate.

Two hydrolysis methods used to obtain rapeseed isolate derivates were compared: chemical hydrolysis performed under alkaline conditions and pepsic proteolysis performed under acidic conditions. The mean molecular weights obtained for the hydrolysates varied from 26 to 2.5 kDa, depending on the level of hydrolysis.

Cloning, bacterial expression, purification and structural characterization of N-terminal-repetitive domain of gamma-Gliadin.

The gene encoding the repetitive domain located in the N-terminal half of gamma-Gliadin from wheat endosperm has been subcloned into a thioredoxin expression system (pET102/D-Topo). It was over-expressed as fusion protein with thioredoxin in Escherichia coli. Thioredoxin was removed by enterokinase cleavage or by acid cleavage at the respective engineered recognition sites.

Identification of IgE-binding epitopes on gliadins for patients with food allergy to wheat.

Background: Food allergy to wheat induces different symptoms as atopic eczema/dermatitis syndrome (AEDS), urticaria and more severe reactions as wheat-dependent exercise-induced anaphylaxis (WDEIA). Different gliadin classes are involved in this allergy but IgE-binding epitopes are known only on omega5-gliadins and for WDEIA cases.

Objectives: The aim of the study was to identify IgE-binding epitopes on several gliadin classes and for several patients with different symptoms and ages.

Rheological interfacial properties of plant protein-arabic gum coacervates at the oil-water interface.

This study concerns the interfacial properties of the plant proteins-arabic gum coacervates, which are involved in encapsulation processes based on complex coacervation. The results make it possible to deduce the prerequisite characteristics of the protein, which are involved in the coacervate interfacial properties. The influence of pH and concentration on protein interfacial properties was also studied so as to enable us to predict the best conditions to achieve encapsulation.

Adsorption kinetics and rheological interfacial properties of plant proteins at the oil-water interface.

Adsorption and rheological properties of plant proteins were determined by means of the dynamic pendant drop technique. The plant protein properties were compared with the interfacial properties of gelatin, which is well-known for its surface-active properties and is commonly used in food and health products. The results showed that alpha gliadins (wheat proteins) and pea globulins have the highest surface active properties at the oil-water interface, even higher than gelatin at the same concentration (weight/volume).

Soy glycinin microcapsules by simple coacervation method.

Encapsulation of a dispersed oil phase (hexadecane) was realized by simple coacervation method using soy glycinin as the wall forming material. Suitable emulsification and coacervation conditions, that favor the formation of microcapsules wall, were identified and investigated. Mild acid (pH 2.

Detailed physicochemical characterization of the 2S storage protein from rape (Brassica napus L.).

Chromatographic, chemical, and spectroscopic techniques were used to characterize the physicochemical properties of napin purified by preparative chromatography. The molar extinction coefficient was determined (epsilon = 0.56), and static and dynamic light scattering measurements enabled the average molecular weight (M(w) = 13919), the second virial coefficient (A(2) = 23.

Properties and microstructure of thermo-pressed wheat gluten films: a comparison with cast films.

Wheat gluten films were prepared by thermo-pressing, and their mechanical properties were compared to those of cast films. The stress-strain relationship was established for films with various amounts of glycerol. Both relationships were quite different, revealing a different network organization.

Data mining techniques to study the disulfide-bonding state in proteins: signal peptide is a strong descriptor.

In the eucaryotic cell, the formation of disulfide bonds takes place in general inside the endoplasmic reticulum which provides a unique folding environment. The DisulfideDB database gathers information about this biological process with structural, evolutionary and neighborhood information on cysteines in proteins. Mining this information with an association rule discovery program permits to extract some strong rules for the prediction of the disulfide-bonding state of cysteines.

Microcapsules based on glycinin-sodium dodecyl sulfate complex coacervation.

Microcapsules processed by complex coacervation were prepared using hexadecane for the oil phase and glycinin (a soybean storage protein)-sodium dodecyl sulfate (SDS) as the main wall-forming material. The study underlines the essential role of SDS, which, by the way of [glycinin(+)-SDS(-)] insoluble complex formation, allowed the precipitation of proteins around oil droplets. Moreover, particular attention was attributed to the study of suitable conditions of glycinin cross-linking with glutaraldehyde.

High microbial production and characterization of strictly periodic polymers modelled on the repetitive domain of wheat gliadins.

Primary structures of wheat prolamins contain repetitive domains involved in the mechanical properties of gluten. In order to experience the ability of recombinant strictly periodic polypeptides, modelled on a consensus sequence of wheat gliadins (PQQPY)(8) and (PQQPY)(17) (SPR8 and SPR17 polypeptides, respectively), to be formulated in film solutions, their heterologous expression conditions, in batch culture and low cell densities, were optimized to match the high requirements of this process. A convenient and general purification procedure was also devised.

Food allergy to wheat: identification of immunogloglin E and immunoglobulin G-binding proteins with sequential extracts and purified proteins from wheat flour.

Background: Cereal-associated allergy is particularly considered a serious problem, because cereals are essential in our daily diet. Wheat proteins are classified into albumins, globulins and prolamins (insoluble gliadins and glutenins).

Objectives: Our objectives were to study the involvement in food allergy to wheat of these different protein types by using purified fractions and to identify those binding IgE and IgG antibodies.

Molecular determinants of the influence of hydrophilic plasticizers on the mechanical properties of cast wheat gluten films.

The influence of a set of hydrophilic plasticizers varying in their chain length (ethyleneglycol and longer molecules) on the tensile strength and elongation at break of cast gluten films was studied. When considered on a molar basis (moles of plasticizer per mole of amino acid), the effect of the different plasticizers depended on their respective molecular weights for plasticizer/amino acid ratios in the range from 0.10 to 0.

Development of an in vitro system simulating bucco-gastric digestion to assess the physical and chemical changes of food.

The release of nutrients from solid food depends on the physical and chemical characteristics of substrates, and on dynamic physiological events including pH, gastric emptying and enzymatic secretion. Our laboratory has developed an in vitro digestive system mimicking mouth and stomach processes to determine physical and chemical changes of bread during digestion. To simulate oral-phase digestion, bread was minced and subjected to in vitro amylase digestion, releasing 219 +/- 11 g oligosaccharides/kg total carbohydrate.

Biopolymeric colloidal carriers for encapsulation or controlled release applications.

Biopolymers represent an interesting alternative to synthetic polymers in order to be used as structured carriers for controlled release and encapsulation applications. In particular, the ability of these carriers to entrap both hydrophilic and hydrophobic drugs may be very promising for many applications. In addition, the absence of chemical compounds and organic solvents used to produce biopolymeric matrices could be very interesting for some industrial applications.

Gliadin matrices for microencapsulation processes by simple coacervation method.

The aim of this study was to use a vegetal protein (gliadin) as a wall-forming component to produce microcapsules. The microencapsulation technique employed was the simple coacervation method and the encapsulated product was a non-food oil, hexadecane. Hexadecane was emulsified by a gliadin solution and the coacervation phenomena induced by adding a salt-solution in the continuous phase of the emulsion containing gliadin.

Reversible changes of the wheat gamma 46 gliadin conformation submitted to high pressures and temperatures.

The structure of the wheat gamma 46 gliadin was investigated, in aqueous solutions, under high pressure or temperature by the use of ultraviolet and fluorescence spectroscopic techniques. We found that high pressure (above 400 MPa) induces a change in the protein conformation that results in a decrease of the polarity of the environment of aromatic amino acids. This new conformation was able to bind the hydrophobic probe, 8-anilino-1-naphtalene-sulfonic acid (ANS), indicating an increase in the gliadin surface hydrophobicity.