Ammonium sulfate-based prefractionation improved proteome coverage and detection of carbonylated proteins in Arabidopsis thaliana leaf extract

Complexation with Alginate in Pumpkin Leaf Protein Solutions for the Encapsulation of Folic Acid: The Effect of Extraction Protocols

This study aimed to assess pumpkin leaves as a protein source and determine the feasibility of these proteins to form complexes with alginate for the encapsulation of folic acid. Different isolation protocols, two based on isoelectric precipitation (one with thermal pretreatment and the other with alkali pre-extraction) and one based on stepwise precipitation with ammonium sulfate, were compared regarding the yield and structural properties of the obtained leaf protein concentrates (LPC). The highest purity of protein was achieved using the thermal-acid protocol and the salting-out protocol at 40% saturation. RuBisCO protein was detected by SDS-PAGE in all LPCs, except for the fractions obtained through salting-out at saturation level ≥ 60%. Complexation of the LPC solutions (1 mg/mL) and sodium alginate solution (10 mg/mL) was monitored as a function of LPC:alginate ratio (2:1, 5:1, and 10:1) and pH (2-8) by zeta-potential measurements and confirmed by FT-IR analysis. Based on the results, the strongest interaction between LPCs and alginate occurred at a pH between 2.20 and 2.80 and an LPC:alginate ratio of 10:1. Complexation resulted in particle yields of 42-71% and folic acid entrapment of 46-92%. The LPC-folic acid interactions elucidated by computational protein-ligand docking demonstrated the high potential of RuBisCO as a biocarrier material for folic acid. The in vitro release study in the simulated gastrointestinal fluids indicated that complexes would be stable in gastric conditions, while folic acid would be gradually released in the intestinal fluids.

Efficient experimental method for purifying allergens from aqueous extracts

Studying the molecular and immunological basis of allergic diseases often requires purified native allergens. The methodologies for protein purification are usually difficult and may not be completely successful. The objective of this work was to describe a methodology to purify allergens from their natural source, while maintaining their native form. The purification strategy consists of a three-step protocol and was used for purifying five specific allergens, Ole e 1, Amb a 1, Alt a 1, Bet v 1 and Cup a 1. Total proteins were extracted in PBS (pH 7.2). Then, the target allergens were pre-purified and enriched by salting-out using increasing concentrations of ammonium sulfate. The allergens were further purified by anion exchange chromatography. Purification of Amb a 1 required an extra step of cation exchange chromatography. The detection of the allergens in the fractions obtained were screened by SDS-PAGE, and Western blot when needed. Further characterization of purified Amb a 1 was performed by mass spectrometry. Ole e 1, Alt a 1, Bet v 1 and Cup a 1 were obtained at > 90 % purity. Amb a 1 was obtained at > 85 % purity. Overall, we propose an easy-to-perform purification approach that allows obtaining highly pure allergens. Since it does not involve neither chaotropic nor organic reagents, we anticipate that the structural and biological functions of the purified molecule remain intact. This method provides a basis for native allergen purification that can be tailored according to specific needs.

Iron Availability Influences Protein Carbonylation in Arabidopsis thaliana Plants

Protein carbonylation is an irreversible form of post-translational modification triggered by reactive oxygen species in animal and plant cells. It occurs either through the metal-catalyzed oxidation of Lys, Arg, Pro, and Thr side chains or the addition of α, β-unsaturated aldehydes and ketones to the side chains of Cys, Lys, and His. Recent genetic studies concerning plants pointed to an implication of protein carbonylation in gene regulation through phytohormones. However, for protein carbonylation to stand out as a signal transduction mechanism, such as phosphorylation and ubiquitination, it must be controlled in time and space by a still unknown trigger. In this study, we tested the hypothesis that the profile and extent of protein carbonylation are influenced by iron homeostasis in vivo. For this, we compared the profile and the contents of the carbonylated proteins in the Arabidopsis thaliana wild-type and mutant-deficient in three ferritin genes under normal and stress conditions. Additionally, we examined the proteins specifically carbonylated in wild-type seedlings exposed to iron-deficient conditions. Our results indicated that proteins were differentially carbonylated between the wild type and the triple ferritin mutant Fer1-3-4 in the leaves, stems, and flowers under normal growth conditions. The profile of the carbonylated proteins was also different between the wild type and the ferritin triple mutant exposed to heat stress, thus pointing to the influence of iron on the carbonylation of proteins. Consistent with this, the exposure of the seedlings to iron deficiency and iron excess greatly influenced the carbonylation of certain proteins involved in intracellular signal transduction, translation, and iron deficiency response. Overall, the study underlined the importance of iron homeostasis in the occurrence of protein carbonylation in vivo.