Solution structure of the C-terminal domain of Ole e 9, a major allergen of olive pollen

Safety evaluation of the food enzyme endo-1,3(4)-β-glucanase from the non-genetically modified Talaromyces versatilis strain PF8

The food enzyme endo-1,3(4)-β-glucanase (3-(1-3;1-4)-β-d-glucan 3(4)-glucanohydrolase; EC 3.2.1.6) is produced with the non-genetically modified Talaromyces versatilis strain PF8 by Erbslöh Geisenheim AG. The food enzyme was free from viable cells of the production organism. It is intended to be used in four food manufacturing processes. Dietary exposure to the food enzyme-total organic solids (TOS) was calculated to be up to 0.110 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 2229 mg TOS/kg bw per day, the highest dose tested, which when compared with the estimated dietary exposure resulted in a margin of exposure of at least 20,264. A search for homology of the amino acid sequence of the food enzyme to known allergens was made and four matches with respiratory or contact allergens were found. The Panel considered that the risk of allergic reactions upon dietary exposure cannot be excluded, but the likelihood is low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns, under the intended conditions of use.

Broad Protection against Invasive Fungal Disease from a Nanobody Targeting the Active Site of Fungal β-1,3-Glucanosyltransferases

Invasive fungal disease accounts for about 3.8 million deaths annually, an unacceptable rate that urgently prompts the discovery of new knowledge-driven treatments. We report the use of camelid single-domain nanobodies (Nbs) against fungal β-1,3-glucanosyltransferases (Gel) involved in β-1,3-glucan transglycosylation. Crystal structures of two Nbs with Gel4 from Aspergillus fumigatus revealed binding to a dissimilar CBM43 domain and a highly conserved catalytic domain across fungal species, respectively. Anti-Gel4 active site Nb3 showed significant antifungal efficacy in vitro and in vivo prophylactically and therapeutically against different A. fumigatus and Cryptococcus neoformans isolates, reducing the fungal burden and disease severity, thus significantly improving immunocompromised animal survival. Notably, C. deneoformans (serotype D) strains were more susceptible to Nb3 and genetic Gel deletion than C. neoformans (serotype A) strains, indicating a key role for β-1,3-glucan remodelling in C. deneoformans survival. These findings add new insight about the role of β-1,3-glucan in fungal biology and demonstrate the potential of nanobodies in targeting fungal enzymes to combat invasive fungal diseases.

Carbohydrate binding modules: Compact yet potent accessories in the specific substrate binding and performance evolution of carbohydrate-active enzymes

Carbohydrate binding modules (CBMs) are independent non-catalytic domains widely found in carbohydrate-active enzymes (CAZymes), and they play an essential role in the substrate binding process of CAZymes by guiding the appended catalytic modules to the target substrates. Owing to their precise recognition and selective affinity for different substrates, CBMs have received increasing research attention over the past few decades. To date, CBMs from different origins have formed a large number of families that show a variety of substrate types, structural features, and ligand recognition mechanisms. Moreover, through the modification of specific sites of CBMs and the fusion of heterologous CBMs with catalytic domains, improved enzymatic properties and catalytic patterns of numerous CAZymes have been achieved. Based on cutting-edge technologies in computational biology, gene editing, and protein engineering, CBMs as auxiliary components have become portable and efficient tools for the evolution and application of CAZymes. With the aim to provide a theoretical reference for the functional research, rational design, and targeted utilization of novel CBMs in the future, we systematically reviewed the function-related characteristics and potentials of CAZyme-derived CBMs in this review, including substrate recognition and binding mechanisms, non-catalytic contributions to enzyme performances, module modifications, and innovative applications in various fields.

Safety evaluation of the food enzyme endo-1,3(4)-β-glucanase from the non-genetically modified Cellulosimicrobium funkei strain AE-TN

The food enzyme endo-1,3(4)-β-glucanase (3-(1-3;1-4)-β-d-glucan 3(4)-glucanohydrolase; EC 3.2.1.6) is produced with the non-genetically modified Cellulosimicrobium funkei strain AE-TN by Amano Enzyme Inc. The food enzyme was shown to contain viable cells of the production strain, which belongs to a species that has been implicated in opportunistic infections in humans. The food enzyme is intended to be used in baking processes and yeast processing. Dietary exposure to the food enzyme total organic solids (TOS) was estimated to be up to 1.75 mg TOS/kg body weight (bw) per day in European populations. Genotoxicity tests did not raise a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a no observed adverse effect level of 1,788 mg TOS/kg bw per day, the highest dose tested, which, when compared with the estimated dietary exposure, resulted in a margin of exposure of at least 1,022. A search for the similarity of the amino acid sequence of the food enzyme to known allergens was made and no match was found. The Panel considered that, under the intended conditions of use, the risk of allergic reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is low. However, due to the presence of viable cells of the production strain in the food enzyme, the Panel concluded that the food enzyme cannot be considered safe.

Properties of a family 56 carbohydrate-binding module and its role in the recognition and hydrolysis of β-1,3-glucan

BH0236 from Bacillus halodurans is a multimodular β-1,3-glucanase comprising an N-terminal family 81 glycoside hydrolase catalytic module, an internal family 6 carbohydrate-binding module (CBM) that binds the nonreducing end of β-1,3-glucan chains, and an uncharacterized C-terminal module classified into CBM family 56. Here, we determined that this latter CBM, BhCBM56, bound the soluble β-1,3-glucan laminarin with a dissociation constant (K_d ) of ∼26 μm and displayed higher affinity for insoluble β-1,3-glucans with K_d values of ∼2-10 μm but lacked affinity for β-1,3-glucooligosaccharides. The X-ray crystal structure of BhCBM56 and NMR-derived chemical shift mapping of the binding site revealed a β-sandwich fold, with the face of one β-sheet possessing the β-1,3-glucan-binding surface. On the basis of the functional and structural properties of BhCBM56, we propose that it binds a quaternary polysaccharide structure, most likely the triple helix adopted by polymerized β-1,3-glucans. Consistent with the BhCBM56 and BhCBM6/56 binding profiles, deletion of the CBM56 from BH0236 decreased activity of the enzyme on the insoluble β-1,3-glucan curdlan but not on soluble laminarin; additional deletion of the CBM6 also did not affect laminarin degradation but further decreased curdlan hydrolysis. The pseudo-atomic solution structure of BH0236 determined by small-angle X-ray scattering revealed structural insights into the nature of avid binding by the BhCBM6/56 pair and how the orientation of the active site in the catalytic module factors into recognition and degradation of β-1,3-glucans. Our findings reinforce the notion that catalytic modules and their cognate CBMs have complementary specificities, including targeting of polysaccharide quaternary structure.

Insights into protein-carbohydrate recognition: A novel binding mechanism for CBM family 43

Despite the growing number of carbohydrate-binding modules (CBMs) that are being uncovered, information on the structural determinants for the sugar-binding regions at atomic resolution is scarce. It is widely accepted that aromatic and H-bonding interactions govern these processes, and reported simulations and theoretical calculations are valuable tools to quantify and understand these interactions. We present here a computational model derived from experimental data that provide a unique atomistic picture of an uncharacterized binding mode of laminarin to the CBM family 43. The present study, which is among the first describing an isolated CBM with the bound carbohydrate, is complemented with quantum mechanical calculations. This allows us to attribute certain experimental observations (binding affinities) to key interactions (H-bonds and aromatic stacking), on the basis of NMR-driven docking structure.

Structural studies of novel glycoconjugates from polymerized allergens (allergoids) and mannans as allergy vaccines

Immunotherapy for treating IgE-mediated allergies requires high doses of the corresponding allergen. This may result in undesired side effects and, to avoid them, hypoallergenic allergens (allergoids) polymerized with glutaraldehyde are commonly used. Targeting allergoids to dendritic cells to enhance cell uptake may result in a more effective immunotherapy. Allergoids coupled to yeast mannan, as source of polymannoses, would be suitable for this purpose, since mannose-binding receptors are expressed on these cells. Conventional conjugation procedures of mannan to proteins use oxidized mannan to release reactive aldehydes able to bind to free amino groups in the protein; yet, allergoids lack these latter because their previous treatment with glutaraldehyde. The aim of this study was to obtain allergoids conjugated to mannan by an alternative approach based on just glutaraldehyde treatment, taking advantage of the mannoprotein bound to the polymannose backbone. Allergoid-mannan glycoconjugates were produced in a single step by treating with glutaraldehyde a defined mixture of allergens derived from Phleum pratense grass pollen and native mannan (non-oxidized) from Saccharomyces cerevisae. Analytical and structural studies, including 2D-DOSY and (1)H-(13)C HSQC nuclear magnetic resonance spectra, demonstrated the feasibility of such an approach. The glycoconjugates obtained were polymers of high molecular weight showing a higher stability than the native allergen or the conventional allergoid without mannan. The allergoid-mannan glycoconjugates were hypoallergenic as detected by the IgE reactivity with sera from grass allergic patients, even with lower reactivity than conventional allergoid without mannan. Thus, stable hypoallergenic allergoids conjugated to mannan suitable for using in immunotherapy can be achieved using glutaraldehyde. In contrast to mannan oxidation, the glutaraldehyde approach allows to preserve mannoses with their native geometry, which may be functionally important for its receptor-mediated recognition.

An Enzymatically Active β-1,3-Glucanase from Ash Pollen with Allergenic Properties: A Particular Member in the Oleaceae Family

Endo-β-1,3-glucanases are widespread enzymes with glycosyl hydrolitic activity involved in carbohydrate remodelling during the germination and pollen tube growth. Although members of this protein family with allergenic activity have been reported, their effective contribution to allergy is little known. In this work, we identified Fra e 9 as a novel allergenic β-1,3-glucanase from ash pollen. We produced the catalytic and carbohydrate-binding domains as two independent recombinant proteins and characterized them from structural, biochemical and immunological point of view in comparison to their counterparts from olive pollen. We showed that despite having significant differences in biochemical activity Fra e 9 and Ole e 9 display similar IgE-binding capacity, suggesting that β-1,3-glucanases represent an heterogeneous family that could display intrinsic allergenic capacity. Specific cDNA encoding Fra e 9 was cloned and sequenced. The full-length cDNA encoded a polypeptide chain of 461 amino acids containing a signal peptide of 29 residues, leading to a mature protein of 47760.2 Da and a pI of 8.66. An N-terminal catalytic domain and a C-terminal carbohydrate-binding module are the components of this enzyme. Despite the phylogenetic proximity to the olive pollen β-1,3-glucanase, Ole e 9, there is only a 39% identity between both sequences. The N- and C-terminal domains have been produced as independent recombinant proteins in Escherichia coli and Pichia pastoris, respectively. Although a low or null enzymatic activity has been associated to long β-1,3-glucanases, the recombinant N-terminal domain has 200-fold higher hydrolytic activity on laminarin than reported for Ole e 9. The C-terminal domain of Fra e 9, a cysteine-rich compact structure, is able to bind laminarin. Both molecules retain comparable IgE-binding capacity when assayed with allergic sera. In summary, the structural and functional comparison between these two closely phylogenetic related enzymes provides novel insights into the complexity of β-1,3-glucanases, representing a heterogeneous protein family with intrinsic allergenic capacity.

The C-terminal domains of two homologous Oleaceae β-1,3-glucanases recognise carbohydrates differently: Laminarin binding by NMR

Ole e 9 and Fra e 9 are two allergenic β-1,3-glucanases from olive and ash tree pollens, respectively. Both proteins present a modular structure with a catalytic N-terminal domain and a carbohydrate-binding module (CBM) at the C-terminus. Despite their significant sequence resemblance, they differ in some functional properties, such as their catalytic activity and the carbohydrate-binding ability. Here, we have studied the different capability of the recombinant C-terminal domain of both allergens to bind laminarin by NMR titrations, binding assays and ultracentrifugation. We show that rCtD-Ole e 9 has a higher affinity for laminarin than rCtD-Fra e 9. The complexes have different exchange regimes on the NMR time scale in agreement with the different affinity for laminarin observed in the biochemical experiments. Utilising NMR chemical shift perturbation data, we show that only one side of the protein surface is affected by the interaction and that the binding site is located in the inter-helical region between α1 and α2, which is buttressed by aromatic side chains. The binding surface is larger in rCtD-Ole e 9 which may account for its higher affinity for laminarin relative to rCtD-Fra e 9.

Molecular Interactions of β-(1→3)-Glucans with Their Receptors

β-(1→3)-Glucans can be found as structural polysaccharides in cereals, in algae or as exo-polysaccharides secreted on the surfaces of mushrooms or fungi. Research has now established that β-(1→3)-glucans can trigger different immune responses and act as efficient immunostimulating agents. They constitute prevalent sources of carbons for microorganisms after subsequent recognition by digesting enzymes. Nevertheless, mechanisms associated with both roles are not yet clearly understood. This review focuses on the variety of elucidated molecular interactions that involve these natural or synthetic polysaccharides and their receptors, i.e., Dectin-1, CR3, glycolipids, langerin and carbohydrate-binding modules.

Allergen ligands in the initiation of allergic sensitization

As investigations into the innate immune responses that lead to allergic sensitization become better defined, there is a need to determine how allergens could interact with pattern recognition receptors that bind non-proteinaceous moieties. Many important allergens are not covalently bound to lipid or carbohydrate, but have structures belonging to lipid, glycan and glycolipid-binding families. These include ML-domain proteins, lipopolysaccharide-binding/cell permeability-increasing proteins, von Ebner gland lipocalins, salivary lipocalins/major urinary proteins, plant pathogenesis-related proteins PR-5 and -10, uteroglobins, non-specific lipid transfer proteins, large lipid transfer proteins and proteins with chitin and other carbohydrate-binding modules. The binding expected is overviewed with regard to importance of the allergens and their ability to elicit responses proposed from experimental models. The evidence compiled showing that allergens from the same source sensitize for different types of adaptive immune responses supports the concept that individual allergens within these sources have their own distinctive interactions with innate immunity.

Structure of allergens and structure based epitope predictions

The structure determination of major allergens is a prerequisite for analyzing surface exposed areas of the allergen and for mapping conformational epitopes. These may be determined by experimental methods including crystallographic and NMR-based approaches or predicted by computational methods. In this review we summarize the existing structural information on allergens and their classification in protein fold families. The currently available allergen-antibody complexes are described and the experimentally obtained epitopes compared. Furthermore we discuss established methods for linear and conformational epitope mapping, putting special emphasis on a recently developed approach, which uses the structural similarity of proteins in combination with the experimental cross-reactivity data for epitope prediction.

Current overview of allergens of plant pathogenesis related protein families

Pathogenesis related (PR) proteins are one of the major sources of plant derived allergens. These proteins are induced by the plants as a defense response system in stress conditions like microbial and insect infections, wounding, exposure to harsh chemicals, and atmospheric conditions. However, some plant tissues that are more exposed to environmental conditions like UV irradiation and insect or fungal attacks express these proteins constitutively. These proteins are mostly resistant to proteases and most of them show considerable stability at low pH. Many of these plant pathogenesis related proteins are found to act as food allergens, latex allergens, and pollen allergens. Proteins having similar amino acid sequences among the members of PR proteins may be responsible for cross-reactivity among allergens from diverse plants. This review analyzes the different pathogenesis related protein families that have been reported as allergens. Proteins of these families have been characterized in regard to their biological functions, amino acid sequence, and cross-reactivity. The three-dimensional structures of some of these allergens have also been evaluated to elucidate the antigenic determinants of these molecules and to explain the cross-reactivity among the various allergens.

The spectrum of olive pollen allergens. From structures to diagnosis and treatment

Olive tree is one of the main allergy sources in Mediterranean countries. The identification of the allergenic repertoire from olive pollen has been essential for the development of rational strategies of standardization, diagnosis, and immunotherapy, all of them focused to increase the life quality of the patients. From its complex allergogram, twelve allergens - Ole e 1 to Ole e 12 - have been identified and characterized to date. Most of them have been cloned and produced as recombinant forms, whose availability have allowed analyzing their three-dimensional structures, mapping their T-cell and B-cell epitopes, and determining the precise allergenic profile of patients for a subsequent patient-tailored immunotherapy. Protein mutant, hypoallergenic derivatives, or recombinant fragments have been also useful experimental tools to analyze the immune recognition of allergens. To test these molecules before using them for clinic purposes, a mouse model of allergic sensitizations has been used. This model has been helpful for assaying different prophylactic approaches based on tolerance induction by intranasal administration of allergens or hypoallergens, used as free or integrated in different delivery systems, and their findings suggest a promising utilization as nasal vaccines. Exosomes - nanovesicles isolated from bronchoalveolar lavage fluid of tolerogenic mice - have shown immunomodulatory properties, being able to protect mice against sensitization to Ole e 1.

Transaldolases are novel and immunoglobulin E cross-reacting fungal allergens

BACKGROUND

Mould-induced atopic respiratory diseases are a worldwide problem. Characterization of fungal allergens is of major clinical importance.

OBJECTIVE

We identified a novel transaldolase family allergen of Cladosporium and Penicillium species.

METHODS

Fungal allergens were identified by immunoblotting, peptide mass mapping and partial sequencing, cDNA cloning and IgE epitope mapping.

RESULTS

A 36.5 kDa IgE-binding component in a partially purified C. cladosporioides preparation was identified. Mass spectrometric analyses suggest that this novel IgE-reacting allergen is a transaldolase. A corresponding full-length 1246 bp cDNA encoding a polypeptide of 325 residues was isolated. The newly identified transaldolase allergen has been designated as Cla c 14.0101. The cDNA encoding the Pencillium chrysogenum transaldolase was isolated by RT-PCR according to the cDNA sequence encoding a P. chrysogenum Wisconsin 54-1255 hypothetical protein. The purified rCla c 14.0101 protein reacted with IgE antibodies in 10 (38%) of 26 Cladosporium cladosporioides-sensitized asthmatic patients. Nine of the 10 rCla c 14.0101-positive sera have IgE binding against the recombinant Penicillium transaldolase (rPen ch 35.0101). Among the eight fungal transaldolase-positive sera tested, three showed IgE binding against the recombinant human transaldolase. To determine cross-reactivity between the Cladosporium and Penicillium fungi, IgE cross-reactivity was detected between these two fungal transaldolase allergens by inhibition assays. Both the N- and the C-terminal fragments of Cla c 14.0101 were recognized by IgE antibodies. The C-terminal IgE-reacting determinant was narrowed down to a region encompassing Thr257 to Ser278 of Cla c 14.0101. It was mapped onto a loop-like structure of a 3D model constructed for Cla c 14.0101.

CONCLUSION AND CLINICAL RELEVANCE

We identified transaldolase as a novel and IgE cross-reactive allergen family of C. cladosporioides and P. chrysogenum. In addition, an IgE-reacting fragment (Thr257 to Ser278) was pinpointed to a loop-like structure on Cla c 14.0101. Results obtained provide important information in clinical mould allergy.

Identification of critical amino acids in an immunodominant IgE epitope of Pen c 13, a major allergen from Penicillium citrinum

Background

Pen c 13, identified as a 33-kDa alkaline serine protease, is a major allergen secreted by Penicillium citrinum. Detailed knowledge about the epitopes responsible for IgE binding would help inform the diagnosis/prognosis of fungal allergy and facilitate the rational design of hypoallergenic candidate vaccines. The goal of the present study was to characterize the IgE epitopes of Pen c 13.

Methodology/Principal Findings

Serum samples were collected from 10 patients with mold allergy and positive Pen c 13 skin test results. IgE-binding epitopes on rPen c 13 were mapped using an enzymatic digestion and chemical cleavage method, followed by dot-blotting and mass spectrometry. A B-cell epitope-predicting server and molecular modeling were used to predict the residues most likely involved in IgE binding. Theoretically predicted IgE-binding regions were further confirmed by site-directed mutagenesis assays. At least twelve different IgE-binding epitopes located throughout Pen c 13 were identified. Of these, peptides S16 (A¹⁴⁸–E¹⁶⁶) and S22 (A²⁴³–K²⁷⁴) were recognized by sera from 90% and 100% of the patients tested, and were further confirmed by inhibition assays. Peptide S22 was selected for further analysis of IgE-binding ability. The results of serum screening showed that the majority of IgE-binding ability resided in the C-terminus. One Pen c 13 mutant, G270A (T²⁶¹–K²⁷⁴), exhibited clearly enhanced IgE reactivity, whereas another, K274A, exhibited dramatically reduced IgE reactivity.

Conclusions/Significance

Experimental analyses confirmed in silico-predicted residues involved in an important antigenic region of Pen c 13. The G270A mutant of Pen c 13 has the potential to serve as an additional tool for the diagnosis/prognosis of mold allergy, and the K274A mutant, as a hypoallergenic form of the epitope, may provide a framework for the design and development of a safe and efficient therapeutic strategy for treating human allergic diseases.

Analysis of olive allergens

Olive pollen is one of the most important causes of seasonal respiratory allergy in Mediterranean countries, where this tree is intensely cultivated. Besides this, some cases of contact dermatitis and food allergy to the olive fruit and olive oil have been also described. Several scientific studies dealing with olive allergens has been reported, being the information available about them constantly increasing. Up to date, twelve allergens have been identified in olive pollen while just one allergen has been identified in olive fruit. This review article describes considerations about allergen extraction and production, also describing the different methodologies employed in the physicochemical and immunological characterization of olive allergens. Finally, a revision of the most relevant studies in the analysis of both olive pollen and olive fruit allergens is carried out.

Molecular mechanisms of yeast cell wall glucan remodeling

Yeast cell wall remodeling is controlled by the equilibrium between glycoside hydrolases, glycosyltransferases, and transglycosylases. Family 72 glycoside hydrolases (GH72) are ubiquitous in fungal organisms and are known to possess significant transglycosylase activity, producing elongated beta(1-3) glucan chains. However, the molecular mechanisms that control the balance between hydrolysis and transglycosylation in these enzymes are not understood. Here we present the first crystal structure of a glucan transglycosylase, Saccharomyces cerevisiae Gas2 (ScGas2), revealing a multidomain fold, with a (betaalpha)(8) catalytic core and a separate glucan binding domain with an elongated, conserved glucan binding groove. Structures of ScGas2 complexes with different beta-glucan substrate/product oligosaccharides provide "snapshots" of substrate binding and hydrolysis/transglycosylation giving the first insights into the mechanisms these enzymes employ to drive beta(1-3) glucan elongation. Together with mutagenesis and analysis of reaction products, the structures suggest a "base occlusion" mechanism through which these enzymes protect the covalent protein-enzyme intermediate from a water nucleophile, thus controlling the balance between hydrolysis and transglycosylation and driving the elongation of beta(1-3) glucan chains in the yeast cell wall.

An Arabidopsis GPI-anchor plasmodesmal neck protein with callose binding activity and potential to regulate cell-to-cell trafficking

Plasmodesmata (Pds) traverse the cell wall to establish a symplastic continuum through most of the plant. Rapid and reversible deposition of callose in the cell wall surrounding the Pd apertures is proposed to provide a regulatory process through physical constriction of the symplastic channel. We identified members within a larger family of X8 domain-containing proteins that targeted to Pds. This subgroup of proteins contains signal sequences for a glycosylphosphatidylinositol linkage to the extracellular face of the plasma membrane. We focused our attention on three closely related members of this family, two of which specifically bind to 1,3-beta-glucans (callose) in vitro. We named this family of proteins Pd callose binding proteins (PDCBs). Yellow fluorescent protein-PDCB1 was found to localize to the neck region of Pds with potential to provide a structural anchor between the plasma membrane component of Pds and the cell wall. PDCB1, PDCB2, and PDCB3 had overlapping and widespread patterns of expression, but neither single nor combined insertional mutants for PDCB2 and PDCB3 showed any visible phenotype. However, increased expression of PDCB1 led to an increase in callose accumulation and a reduction of green fluorescent protein (GFP) movement in a GFP diffusion assay, identifying a potential association between PDCB-mediated callose deposition and plant cell-to-cell communication.

Mapping of IgE-binding epitopes on the major latex allergen Hev b 2 and the cross-reacting 1,3beta-glucanase fruit allergens as a molecular basis for the latex-fruit syndrome

Nine distinct IgE-binding epitopes were identified along the entire amino acid sequence of the major latex allergen Hev b 2 (1,3beta-glucanase) using a set of synthetic 15-mer peptides frameshifted by 3 residues immobilized on cellulose membrane (Spot technique). Most of the amino acid residues building these IgE-binding epitopic regions are nicely exposed on the surface and the epitopes usually correspond to charged regions on the molecular surface of the protein. A smaller number of 5 IgE-binding epitopic areas was identified on the banana 1,3beta-glucanase, which exhibits a very similar overall conformation and charge distribution. The latter epitopes might be responsible for the IgE-binding cross-reactivity currently observed in the latex-fruit syndrome. Using rabbit polyclonal IgG anti-BanGluc as a probe instead of IgE from allergic patients the same epitopic regions were identified in both Hev b 2 and BanGluc. Additionally, surface-exposed regions with a very close conformation were predicted to occur on Ole e 9, the 1,3beta-glucanase allergen identified in olive pollen.