The identification of allergen proteins in sugar beet (Beta vulgaris) pollen causing occupational allergy in greenhouses

<p>Abstract</p> <p>Background</p> <p>During production of sugar beet (<it>Beta vulgaris</it>) seeds in greenhouses, workers frequently develop allergic symptoms. The aim of this study was to identify and characterize possible allergens in sugar beet pollen.</p> <p>Methods</p> <p>Sera from individuals at a local sugar beet seed producing company, having positive SPT and specific IgE to sugar beet pollen extract, were used for immunoblotting. Proteins in sugar beet pollen extracts were separated by 1- and 2-dimensional electrophoresis, and IgE-reactive proteins analyzed by liquid chromatography tandem mass spectrometry.</p> <p>Results</p> <p>A 14 kDa protein was identified as an allergen, since IgE-binding was inhibited by the well-characterized allergen Che a 2, profilin, from the related species <it>Chenopodium album</it>. The presence of 17 kDa and 14 kDa protein homologues to both the allergens Che a 1 and Che a 2 were detected in an extract from sugar beet pollen, and partial amino acid sequences were determined, using inclusion lists for tandem mass spectrometry based on homologous sequences.</p> <p>Conclusion</p> <p>Two occupational allergens were identified in sugar beet pollen showing sequence similarity with <it>Chenopodium </it>allergens. Sequence data were obtained by mass spectrometry (70 and 25%, respectively for Beta v 1 and Beta v 2), and can be used for cloning and recombinant expression of the allergens. As for treatment of <it>Chenopodium </it>pollinosis, immunotherapy with sugar beet pollen extracts may be feasible.</p

Detection of Crosslinks within and between Proteins by LC-MALDI-TOFTOF and the Software FINDX to Reduce the MSMS-Data to Acquire for Validation

Lysine-specific chemical crosslinking in combination with mass spectrometry is emerging as a tool for the structural characterization of protein complexes and protein-protein interactions. After tryptic digestion of crosslinked proteins there are thousands of peptides amenable to MSMS, of which only very few are crosslinked peptides of interest. Here we describe how the advantage offered by off-line LC-MALDI-TOF/TOF mass spectrometry is exploited in a two-step workflow to focus the MSMS-acquisition on crosslinks mainly. In a first step, MS-data are acquired and all the peak list files from the LC-separated fractions are merged by the FINDX software and screened for presence of crosslinks which are recognized as isotope-labeled doublet peaks. Information on the isotope doublet peak mass and intensity can be used as search constraints to reduce the number of false positives that match randomly to the observed peak masses. Based on the MS-data a precursor ion inclusion list is generated and used in a second step, where a restricted number of MSMS-spectra are acquired for crosslink validation. The decoupling of MS and MSMS and the peptide sorting with FINDX based on MS-data has the advantage that MSMS can be restricted to and focused on crosslinks of Type 2, which are of highest biological interest but often lowest in abundance. The LC-MALDI TOF/TOF workflow here described is applicable to protein multisubunit complexes and using 14N/15N mixed isotope strategy for the detection of inter-protein crosslinks within protein oligomers

A comparison of psoriasis severity in pediatric patients treated with methotrexate vs biologic agents

This cohort study compares the use of methotrexate vs biologic agents in children with moderate to severe psoriasis. Question What is the association between use of methotrexate vs biologics and psoriasis severity and drug survival (rate and duration of adherence to a specific drug regimen) in pediatric patients with moderate to severe psoriasis? Findings In this cohort study including 234 pediatric patients with moderate to severe psoriasis, those receiving biologics were more likely than those treated with methotrexate to achieve a Physician Global Assessment status of clear/almost clear and 75% or more improvement of the Psoriasis Area and Severity Index rating at 6 months. In addition, biologics were associated with better drug survival rates at 1, 3, and 5 years, with comparable discontinuation rates owing to lack of response. Meaning In pediatric patients with psoriasis, treatment with biologics may be associated with a significantly greater reduction in psoriasis severity than methotrexate; nevertheless, with 35.6% of the patients achieving clear/almost clear and 40.0% reaching 75% or more improvement on the Psoriasis Area and Severity Index, methotrexate remains an effective treatment for pediatric psoriasis. Importance Few studies have compared the use of methotrexate and biologics, the most commonly used systemic medications for treatment of moderate to severe psoriasis in children. Objective To assess the real-world, 6-month reduction in psoriasis severity and long-term drug survival (rate and duration of adherence to a specific drug) of methotrexate vs biologics in plaque psoriasis in children. Design, Setting, and Participants A retrospective medical records review was conducted at 20 European and North American centers. Treatment response was based on site-reported Psoriasis Area and Severity Index (PASI) and/or Physician Global Assessment (PGA) scores at baseline and within the first 6 months of treatment. Participants included all 234 consecutively seen children with moderate to severe psoriasis who received at least 3 months of methotrexate or biologics from December 1, 1990, to September 16, 2014, with sufficient data for analysis. Data analysis was performed from December 14, 2015, to September 1, 2016. Main Outcomes and Measures PASI, with a range from 0 to 72 (highest score indicating severe psoriasis), and/or PGA, with a scale of 0 (clear), 1 (minimal), 2 (mild), 3 (moderate), 4 (severe), and 5 (very severe). Results Of 234 pediatric patients (103 boys [44.0%]; 131 girls [56.0%]) treated with methotrexate and/or biologics, 163 patients (69.7%) exclusively received methotrexate, 47 patients (20.1%) exclusively received biologics, and 24 children (10.2%) received methotrexate and biologics sequentially. Of the latter cohort, 23 children were treated initially with methotrexate. Mean (SD) age at initiation was 11.6 (3.7) years for methotrexate and 13.3 (2.9) years for biologics (73.2% for etanercept) (P = .002). Among patients evaluated by a scoring method at 6-month follow-up, 75% or greater improvement in PASI (PASI75) was achieved in 12 of 30 patients (40.0%) receiving methotrexate and 20 of 28 patients (71.4%) receiving biologics, and PGA was clear/almost clear (PGA 0/1) in 41 of 115 patients (35.6%) receiving methotrexate and 18 of 37 patients (48.6%) receiving biologics. Achieving PASI75 and/or PGA 0/1 between baseline and 6 months was more likely with biologics than methotrexate (PASI75: odds ratio [OR], 4.56; 95% CI, 2.02-10.27; P < .001; and PGA 0/1: OR, 2.00; 95% CI, 0.98-4.00; P = .06). Decreased mean PASI and PGA scores were associated with biologics more than with methotrexate (PASI effect, -3.13; 95% CI, -4.33 to -1.94; P < .001; and PGA effect, -0.31; 95% CI, -0.56 to -0.06; P = .02). After 1, 3, and 5 years of use, overall drug survival rates for methotrexate were 77.5%, 50.3%, and 35.9%, and for biologics, the rates were 83.4%, 64.3%, and 57.1%, respectively. Biologics were associated with a better confounder-corrected drug survival than methotrexate (hazard ratio [HR], 2.23; 95% CI, 1.21-4.10; P = .01). Discontinuation owing to lack of response was comparable (HR, 1.64; 95% CI, 0.80-3.36; P = .18). Conclusions and Relevance Methotrexate and biologics appear to be associated with improvement in pediatric psoriasis, although biologics seem to be associated with greater reduction in psoriasis severity scores and higher drug survival rates than methotrexate in the real-world setting. Additional studies directly comparing these medications should be performed for confirmation

Exploring small heat shock protein chaperones by crosslinking mass spectrometry

Together with other molecular chaperones, small heat shock proteins are key components of the protein quality control system, which is comprised of several hundred proteins and acts to maintain proteome homeostasis in the cell. Small heat shock proteins bind unfolding proteins at an early stage, to prevent these from further unfolding and aggregating. Partially unfolded proteins are being held in a refolding competent state, to be refolded by other chaperones or degraded by the degradation machinery. In the stress response, small heat shock proteins are among the most highly upregulated, preparing the cell to absorb large quantities of partially unfolded proteins. In this way, they form the first line of defence against the threat of protein aggregation under stress conditions. The polydispersity and dynamics of the large small heat shock protein oligomers have complicated their structural and functional characterization. In particular, the molecular mechanism of substrate protein protection remains poorly understood. The work described in this thesis aims to characterize the molecular interactions between the plant small heat shock protein Hsp21 and model substrate proteins by crosslinking mass spectrometry. The model substrate proteins citrate synthase and malate dehydrogenase, both especially vulnerable to temperature-induced aggregation, were protected from aggregation by Hsp21 and therefore used to investigate the Hsp21-substrate interactions that confer protection. To be able to study the transient Hsp21-substrate interaction by crosslinking mass spectrometry, a workflow was developed based on isotope-labelled lysine-specific crosslinking, nano-LC MALDI-TOF/TOF mass spectrometry, and data analysis with the specialized software FINDX. During the development of this workflow, interactions within Hsp21 itself were characterized as a way to evaluate the method and to learn more about the conformation of Hsp21 in absence of substrate. The interpretation of the identified Hsp21-Hsp21 crosslinks required structural information on the Hsp21 oligomer, which was obtained by single particle negative stain electron microscopy. The combination of these data with native mass spectrometry and homology modelling, led to a structure model of the Hsp21 dodecamer. The in-depth analysis of Hsp21-Hsp21 crosslinks provided a framework for further application of the crosslinking mass spectrometry workflow to the Hsp21-substrate interactions. Finally, Hsp21-substrate crosslinks were identified that support the view that unfolding substrate proteins interact with the intrinsically disordered N-terminal region of the small heat shock protein Hsp21

Probing the transient interaction between the small heat-shock protein Hsp21 and a model substrate protein using crosslinking mass spectrometry.

Small heat-shock protein chaperones are important players in the protein quality control system of the cell, because they can immediately respond to partially unfolded proteins, thereby protecting the cell from harmful aggregates. The small heat-shock proteins can form large polydisperse oligomers that are exceptionally dynamic, which is implicated in their function of protecting substrate proteins from aggregation. Yet the mechanism of substrate recognition remains poorly understood, and little is known about what parts of the small heat-shock proteins interact with substrates and what parts of a partially unfolded substrate protein interact with the small heat-shock proteins. The transient nature of the interactions that prevent substrate aggregation rationalize probing this interaction by crosslinking mass spectrometry. Here, we used a workflow with lysine-specific crosslinking and offline nano-liquid chromatography matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry to explore the interaction between the plant small heat-shock protein Hsp21 and a thermosensitive model substrate protein, malate dehydrogenase. The identified crosslinks point at an interaction between the disordered N-terminal region of Hsp21 and the C-terminal presumably unfolding part of the substrate protein

Chemical cross-linking of the chloroplast localized small heat-shock protein, Hsp21, and the model substrate citrate synthase

The molecular mechanism whereby the small heat-shock protein (sHsp) chaperones interact with and prevent aggregation of other proteins is not fully understood. We have characterized the sHsp–substrate protein interaction at normal and increased temperatures utilizing a model substrate protein, citrate synthase (CS), widely used in chaperone assays, and a dodecameric plant sHsp, Hsp21, by chemical cross-linking with 3,3′-Dithiobis[sulfosuccinimidylpropionate] (DTSSP) and mass spectrometric peptide mapping. In the absence of CS, the cross-linker captured Hsp21 in dodecameric form, even at increased temperature (47°C). In the presence of equimolar amounts of CS, no Hsp21 dodecamer was captured, indicating a substrate-induced Hsp21 dodecamer dissociation by equimolar amounts of CS. Cross-linked Hsp21–Hsp21 dipeptides indicated an exposure of the Hsp21 C-terminal tails and substrate-binding sites normally covered by the C terminus. Cross-linked Hsp21–CS dipeptides mapped to several sites on the surface of the CS dimer, indicating that there are numerous weak and short-lived interactions between Hsp21 and CS, even at normal temperatures. The N-terminal arms especially interacted with a motif in the CS dimer, which is absent in thermostable forms of CS. The cross-linking data suggest that the presence of substrate rather than temperature influences the conformation of Hsp21

Redox-induced structural changes in the di-iron and di-manganese forms of Bacillus anthracis ribonucleotide reductase subunit NrdF suggest a mechanism for gating of radical access

Class Ib ribonucleotide reductases (RNR) utilize a di-nuclear manganese or iron cofactor for reduction of superoxide or molecular oxygen, respectively. This generates a stable tyrosyl radical (Y·) in the R2 subunit (NrdF), which is further used for ribonucleotide reduction in the R1 subunit of RNR. Here, we report high-resolution crystal structures of Bacillus anthracis NrdF in the metal-free form (1.51 Å) and in complex with manganese (MnII/MnII, 1.30 Å). We also report three structures of the protein in complex with iron, either prepared anaerobically (FeII/FeII form, 1.32 Å), or prepared aerobically in the photo-reduced FeII/FeII form (1.63 Å) and with the partially oxidized metallo-cofactor (1.46 Å). The structures reveal significant conformational dynamics, likely to be associated with the generation, stabilization, and transfer of the radical to the R1 subunit. Based on observed redox-dependent structural changes, we propose that the passage for the superoxide, linking the FMN cofactor of NrdI and the metal site in NrdF, is closed upon metal oxidation, blocking access to the metal and radical sites. In addition, we describe the structural mechanics likely to be involved in this process