NMR resonance assignments of the pathogenesis-related peach allergen Pru p 1.0101

The PR-10 Protein Pru p 1 is an Endonuclease that Preferentially Cleaves Single-Stranded RNA

Pathogenesis-related class 10 (PR-10) proteins play a crucial role in plant defense by acting as ribonucleases. The specific mechanism of action and substrate specificity of these proteins have remained largely unexplored so far. In this study, we elucidate the enzymatic activity of Pru p 1, a PR-10 protein from peach. We demonstrate that this protein catalyzes the endonucleolytic backbone cleavage of RNA substrates into short oligonucleotides. Initial cleavage products, identified through kinetic analysis, can bind again, priming them for further degradation. NMR binding site mapping reveals that the large internal cavity of Pru p 1, which is characteristic for PR-10 proteins, serves as an anchoring site for single-stranded ribonucleotide chains. We propose a structure-based mechanistic model that accounts for the observed cleavage patterns and the inhibitory effect of zeatin, a nucleoside analog, on the ribonuclease activity of Pru p 1.

The Structural Flexibility of PR-10 Food Allergens

PR-10 proteins constitute a major cause of food allergic reactions. Birch-pollen-related food allergies are triggered by the immunologic cross-reactivity of IgE antibodies with structurally homologous PR-10 proteins that are present in birch pollen and various food sources. While the three-dimensional structures of PR-10 food allergens have been characterized in detail, only a few experimental studies have addressed the structural flexibility of these proteins. In this study, we analyze the millisecond-timescale structural flexibility of thirteen PR-10 proteins from prevalent plant food sources by NMR relaxation-dispersion spectroscopy, in a comparative manner. We show that all the allergens in this study have inherently flexible protein backbones in solution, yet the extent of the structural flexibility appears to be strikingly protein-specific (but not food-source-specific). Above-average flexibility is present in the two short helices, α1 and α2, which form a V-shaped support for the long C-terminal helix α3, and shape the internal ligand-binding cavity, which is characteristic for PR-10 proteins. An in-depth analysis of the NMR relaxation-dispersion data for the PR-10 allergen from peanut reveals the presence of at least two subglobal conformational transitions on the millisecond timescale, which may be related to the release of bound low-molecular-weight ligands from the internal cavity.

Rosaceae food allergy: a review

This review provides a global overview on Rosaceae allergy and details the particularities of each fruit allergy induced by ten Rosaceae species: almond/peach/cherry/apricot/plum (Amygdaleae), apple/pear (Maleae), and raspberry/blackberry/strawberry (Rosoideae). Data on clinical symptoms, prevalence, diagnosis, and immunotherapies for the treatment of Rosaceae allergy are herein stated. Allergen molecular characterization, cross-reactivity/co-sensitization phenomena, the impact of food processing and digestibility, and the methods currently available for the Rosaceae detection/quantification in foods are also described. Rosaceae allergy has a major impact in context to pollen-food allergy syndrome (PFAS) and lipid transfer protein (LTP) allergies, being greatly influenced by geography, environment, and presence of cofactors. Peach, apple, and almond allergies are probably the ones most affecting the quality of life of the allergic-patients, although allergies to other Rosaceae fruits cannot be overlooked. From patients' perspective, self-allergy management and an efficient avoidance of multiple fruits are often difficult to achieve, which might raise the risk for cross-reactivity and co-sensitization phenomena and increase the severity of the induced allergic responses with time. At this point, the absence of effective allergy diagnosis (lack of specific molecular markers) and studies advancing potential immunotherapies are some gaps that certainly will prompt the progress on novel strategies to manage Rosaceae food allergies.

Skin Testing With Peach Peel Extract Versus Serum IgE to Pru p 3 as a Stronger Predictor of Peach-Induced Anaphylaxis

The most important peach fruit allergen is Pru p 3, followed by Pru p 1, Pru p 4, and Pru p 7. We aimed to assess their role in subjects with peach fruit-induced allergy (anaphylaxis and OAS) and compare skin prick tests (SPT) vs. specific immunoglobulin E (sIgE) for predicting anaphylaxis. We also selected a control group. SPT included prevalent inhalant and plant food allergens plus peach peel extract. The sIgE to Pru p 1, Pru p 3, Pru p 4, and Pru p 7 were quantified. Compared with controls (n = 42), cases (n = 41) were younger (P = 0.003), more frequently female (P < 0.05) and had higher SPT positivity to peach peel (44% vs. 2.4%, P < 0.0001). There were significant differences in sensitization to several pollens: Olea europaea, Artemisia vulgaris, Prunus persica, Platanus acerifolia (all P < 0.001); and fruits: apple (P < 0.04), peanut (P < 0.002), tomato (P < 0.005), and melon (P < 0.05). Pru p 3 sIgE was detected in 61% of all cases (85% anaphylaxis and 38% OAS; P < 0.01 each) and 5% of controls (P < 0.001). Pru p 4 sIgE was present in 19% of cases and 7% of controls. The sIgE to Pru p 1 and Pru p 7 were not found. The odds ratio to predict anaphylaxis for peach peel SPT was 113 (confidence interval [CI], 20–613; P < 0.0001); for sIgE to Pru p 3, 22 (CI, 5.3–93; P < 0.0001); and for SPT positivity to selected plant food allergens, 5 (CI, 1–19; P < 0.05). In our study group, SPT with peel peach extract was a better predictor of anaphylaxis than Pru p 3 sIgE or other variables considered. The role of sIgE to Pru p 1, Pru p 4, and Pru p 7 seemed negligible.

Structure and Zeatin Binding of the Peach Allergen Pru p 1

Peach (Prunus persica) is among the fruits most frequently reported to cause food allergies. Allergic reactions commonly result from previous sensitization to the birch pollen allergen Bet v 1, followed by immunological cross-reactivity of IgE antibodies to structurally related proteins in peach. In this study, we present the three-dimensional NMR solution structure of the cross-reactive peach allergen Pru p 1 (isoform Pru p 1.0101). This 17.5 kDa protein adopts the canonical Bet v 1 fold, composed of a seven-stranded β-sheet and three α-helices enclosing an internal cavity. In Pru p 1, the inner surface of the cavity contains an array of hydroxyl-bearing amino acids surrounded by a hydrophobic patch, constituting a docking site for amphiphilic molecules. NMR-guided docking of the cytokinin molecule zeatin to the internal cavity of Pru p 1 provides a structure-based rationale for the effect that zeatin binding has on the protein's RNase activity.

NMR resonance assignments of the four isoforms of the hazelnut allergen Cor a 1.04

In large parts of Europe, Northern America and China people are suffering from allergies after consuming certain kinds of fruits and vegetables. Typical allergic symptoms range from scratching and itching of the throat to severe symptoms like rhino conjunctivitis and anaphylaxis. For hazelnuts (Corylus avellana), these allergies result from initial sensitization to the birch (Betula verrucosa) pollen allergen Bet v 1 and subsequent development of allergic cross-reactions to proteins that are similar in their three-dimensional structure to the sensitizing protein Bet v 1. The cross-reactive proteins in hazelnut are the four isoforms Cor a 1.04 with a molecular weight of about 17.5 kDa. Significant differences regarding the immunologic behavior of these proteins have been reported. In this work we assigned backbone and side chain ¹H, ¹³C, and ¹⁵N chemical shifts of these four isoforms, Cor a 1.0401, Cor a 1.0402, Cor a 1.0403, and Cor a 1.0404 by solution NMR spectroscopy. The chemical shift data confirm the characteristic Bet v onefold for all four isoforms, consisting of seven β-strands that are separated by two short α-helices, along with a long C-terminal α-helix. These data provide the basis for a comparative structural and dynamic analysis of these proteins by NMR in order to characterize their different immunologic cross-reactivities on a molecular level.