New exploration of the γ-gliadin structure through its partial hydrolysis

The partial enzymatic hydrolysis of wheat gliadins constitutes an interesting tool to unravel their structural specificity. In this work, the structure and conformation of γ-gliadin were investigated through its limited chymotrypsic digestion. Using a combination of computational, biochemical and biophysical tools, we studied each of its N and C terminal domains. Our results reveal that γ-gliadin is a partially disordered protein with an unfolded N-terminal domain surprisingly resistant to chymotrypsin and a folded C-terminal domain. Using spectroscopic tools, we showed that structural transitions occured over the disordered N-terminal domain for decreasing ethanol/water ratios. Using SAXS measurements, low-resolution 3D structures of γ-gliadin were proposed. To relate the repeated motifs of the N-terminal domain of γ-gliadin to its structure, engineered peptide models PQQPY/F were also studied. Overall results demonstrated similarities between the N-terminal domain and its derived model peptides. Our findings support the use of these peptides as general templates for understanding the wheat protein assembly and dynamics

SEEDQUAL : Caractérisation de la diversité génétique de la composition de la graine et du tourteau de colza pour des usages en alimentation animale

National audienc

Towards a reproducible and high‐throughput workflow to quantify globulins and napins, the two major seed storage proteins in oilseed rape

International audienceSeed storage proteins (SSP) in oilseed rape consist of 12S globulins (cruciferins) and 2S albumins (napins) that stand for around 70% of total seed proteins. Since napins contain more sulfur residues than cruciferins, they display a higher value for food or feed usages. Recent results demonstrated the potentialities of genetics to improve the 12S/2S ratio. However, the current methods to assess the SSP balance are still time consuming and difficult to handle, thus preventing the phenotyping of large sets of accessions. Plant material 100 accessions of winter oilseed rape : Conclusion: Encouraging results for 2S quantification with NIRS. The current calibrations can be used to roughly sort out the accessions upon 12S/2S content but need further improvements (e.g., wider calibration sets)

Évaluation de deux méthodes d’auto-tannage de fractions de tourteaux de tournesol et de colza enrichies en protéines et composés phénoliques par mesure de la dégradabilité ruminale des protéines in vitro

International audienceTwo protein tanning methods were evaluated to contribute to the withdrawal of formaldehyde as a tanning agent of meals for feeding ruminants. The experimental materials were two fractions of rapeseed and sunflower meals collected at the positive electrode of an electrostatic separator, presenting high contents in proteins and phenolic compounds. The objective was to make phenolics and proteins interact without addition of exogenous tannins. Treatment CH incubated a meal fraction:water mixture (1:2, w:w) for 48 h at 50 degrees C. Treatment FR incubated a meal fraction:water mixture (1:10, w:w) at pH 9.0 for 48 h at 4 degrees C. Microbial proteolysis on meal fractions were quantified during 24 h rumen batch fermentations with cellulose and starch as nitrogen-free energy sources. The net production of ammonia tended to be reduced by treatment FR mostly on rapeseed, corresponding to an 8% saving of rapeseed meal proteins degradable in the rumen. When untreated, the sunflower fraction decreased methane production by 50%, while treatments restored the fermentation pattern. Cold alkaline treatment could be considered to protect meal proteins from degradation by rumen micro-organisms.Deux méthodes de tannage des protéines ont été évaluées pour contribuer au remplacement du formaldéhyde comme agent tannant des tourteaux destinés à l’alimentation des ruminants. Les matériaux expérimentaux étaient deux fractions de tourteaux de colza et tournesol collectées à l’électrode positive d’un séparateur électrostatique, présentant des teneurs élevées en protéines et en composés phénoliques. Le but était de faire interagir les composés phénoliques et les protéines sans addition de tanins exogènes. Le traitement CH a consisté à incuber un mélange tourteau/eau (1/2, poids/poids) pendant 48 h à 50 °C. Le traitement FR a consisté à incuber un mélange tourteau/eau (1/10, poids/poids) à pH 9,0 pendant 48 h à 4 °C. La protéolyse des fractions de tourteau par les microbes du rumen a été quantifiée lors de fermentations in vitro de 24 h avec de la cellulose et de l’amidon comme sources d’énergie sans azote. Le traitement FR a eu tendance à réduire la production nette d’ammoniac, principalement avec le colza, équivalant à la protection de 8 % des protéines de tourteau de colza dégradables dans le rumen. La fraction de tournesol non traitée a diminué la production de méthane de 50 %, cependant les traitements ont restauré le profil fermentaire. Le traitement alcalin à froid pourrait être envisagé afin de protéger les protéines du tourteau de la dégradation par les micro-organismes du rume

Lien entre composition en protéines de réserve et teneurs en glucosinolates dans la graine de colza : vers l’identification de déterminants génétiques et moléculaires

National audienceIn rapeseed, the seed storage proteins are cruciferins (12S globulins) and napins (2S albumins) which represent more than 70% of the total proteins. As napins are richer in sulfur and aromatic residues than cruciferins, they are of greater nutritional interest. However, several studies show that in modern varieties '00' (no erucic acid and low glucosinolates), the napins content is lower than in old varieties '++' (high erucic acid and glucosinolates). The aim of our study is to identify the genetic and molecular bases of the relationship between the glucosinolate and 2S contents in rapeseed.Association genetic analysis identified eight genomic regions controlling both napin and glucosinolate contents. These regions cover nearly 650 genes, seven are described involved in sulfur metabolism pathways and were targeted in this study. In particular, the MYB28 gene, located on chromosome C09, shows a 4-bp insertion polymorphism between the '00' and '++' varieties. Furthermore, MYB28 insertion mutants in Arabidopsis produce seeds with significantly reduced sulfur, glucosinolates and napins contents. These results could provide clues for improving the reserve protein composition of rapeseed.Chez le colza, les protéines de réserve de la graine sont les cruciférines (globulines 12S) et les napines (albumines 2S) qui représentent plus de 70% des protéines totales. Les napines étant plus riches en résidus soufrés et aromatiques que les cruciférines, elles présentent un intérêt supérieur sur le plan nutritionnel. Cependant plusieurs études montrent que chez les variétés modernes de colza, ‘00’, dont les graines sont dépourvues en acide érucique et pauvres en glucosinolates, la teneur en napines est plus faible que chez les variétés anciennes ‘++’. L’objectif de notre étude est d’identifier les bases génétiques et moléculaires de la relation entre la teneur en glucosinolates et en napines dans la graine de colza.Une analyse par génétique d’association a permis d’identifier huit régions génomiques contrôlant à la fois les teneurs en napines et en glucosinolates. Ces régions couvrent près de 650 gènes dont sept sont décrits comme étant impliqués dans les voies du métabolisme soufré et ont été ciblés pour la suite de cette étude. En particulier, le gène MYB28, localisé sur le chromosome C09, montre un polymorphisme d’insertion de 4 pb entre les variétés ‘00’ et ‘++’. Par ailleurs, des mutants d’insertion MYB28 chez Arabidopsis produisent des graines dont les teneurs en soufre, glucosinolates et napines sont significativement réduites. Ces résultats pourraient fournir des pistes pour améliorer la composition en protéines de réserve de la graine de colza

Assembly of plant storage proteins: role of intrinsic disorder and charge anisotropy

Assembly of plant storage proteins: role of intrinsic disorder and charge anisotropy. Edible Soft Matter – a SoftComp Topical Worksho

Assembly of plant storage proteins: role of intrinsic disorder and charge anisotropy

Assembly of plant storage proteins: role of intrinsic disorder and charge anisotropy. Edible Soft Matter – a SoftComp Topical Worksho

Biochemical and physical–chemical characterisation of leaf proteins extracted from Cichorium endivia leaves

International audienceThis study provides a detailed characterisation of a leaf protein concentrate (LPC) extracted from Cichorium endivia leaves using a pilot scale process. This concentrate contains 74.1% protein and is mainly composed of Ribulose-1,5-BISphosphate Carboxylase/Oxygenase (RuBisCO). We show that the experimentally determined extinction coefficient (around 5.0 cm−1 g−1 L depending on the pH) and refractive index increment (between 0.27 and 0.39 mL g−1) are higher than the predicted ones (about 1.6 cm−1 g−1 L and 0.19 mL g−1, respectively). In addition, the UV–visible absorption spectra show a maximum at 258 nm. These data suggest the presence of non-protein UV-absorbing species. Chromatographic separation of the concentrate components in denaturing conditions suggests that RuBisCO SC may be covalently bounded to few phenolic compounds. Besides, the solubility of LPC proteins is higher than 90% above pH 6. Such high solubility could make LPC a good candidate as a functional food ingredient