A Collagen-Binding S-Layer Protein in Lactobacillus crispatus

Two S-layer-expressing strains, Lactobacillus crispatus JCM 5810 and Lactobacillus acidophilus JCM 1132, were assessed for adherence to proteins of the mammalian extracellular matrix. L. crispatus JCM 5810 adhered efficiently to immobilized type IV and I collagens, laminin, and, with a lower affinity, to type V collagen and fibronectin. Strain JCM 1132 did not exhibit detectable adhesiveness. Within the fibronectin molecule, JCM 5810 recognized the 120-kDa cell-binding fragment of the protein, while no bacterial adhesion to the amino-terminal 30-kDa or the gelatin-binding 40-kDa fragment was detected. JCM 5810 but not JCM 1132 also bound (sup125)I-labelled soluble type IV collagen, and this binding was efficiently inhibited by unlabelled type IV and I collagens and less efficiently by type V collagen, but not by laminin or fibronectin. L. crispatus JCM 5810 but not L. acidophilus JCM 1132 also adhered to Matrigel, a reconstituted basement membrane preparation from mouse sarcoma cells, as well as to the extracellular matrix prepared from human Intestine 407 cells. S-layers from both strains were extracted with 2 M guanidine hydrochloride, separated by electrophoresis, and transferred to nitrocellulose sheets. The S-layer protein from JCM 5810 bound (sup125)I-labelled type IV collagen, whereas no binding was seen with the S-layer protein from JCM 1132. Binding of (sup125)I-collagen IV to the JCM 5810 S-layer protein was effectively inhibited by unlabelled type I and IV collagens but not by type V collagen, laminin, or fibronectin. It was concluded that L. crispatus JCM 5810 has the capacity to adhere to human subintestinal extracellular matrix via a collagen-binding S-layer.

Hev b 6.01 and Hev b 5 induce pro-inflammatory cytokines and chemokines from peripheral blood mononuclear cells in latex allergy

BACKGROUND

Hev b 6.01 (prohevein) and Hev b 5 [acidic natural rubber latex (NRL) protein] are major IgE-binding allergens in NRL allergy.

OBJECTIVE

To examine allergen-specific cytokine and chemokine responses in NRL-allergic patients.

METHODS

Fourteen NRL-allergic patients and 10 healthy controls participated in the study. Hev b 6.01 and Hev b 5 were purified under non-denaturating conditions by chromatographic methods. Specific IgE antibodies were measured by ELISA and proliferation of peripheral blood mononuclear cells (PBMC) by (3)H-thymidine incorporation assay. Allergen-specific induction of cytokine and chemokine mRNA in PBMC was measured by real-time PCR and protein levels by ELISA. Surface expression of chemokine receptors was analysed by flow cytometry.

RESULTS

Twelve (86%) NRL-allergic patients had positive skin prick test reactions and IgE antibodies against Hev b 6.01, but less than 30% responded to Hev b 5. Cell proliferation against Hev b 6.01, but not against Hev b 5, was significantly increased. Both allergens elicited significantly higher expression of pro-inflammatory and T-helper type 2 cytokines (TNF, IL-12p40, IL-13) and chemokines (CCL3, CCL4, CCL20) in the NRL-allergic patients than in controls. Interestingly, mRNA expression of the regulatory cytokine TGF-beta1 was reduced, whereas IL-10 expression was enhanced after allergen stimulations in patients with NRL allergy. Finally, the NRL-allergic patients showed increased CCR4 expression on CD3(+)CD8(-) T cells and decreased CXCR3 expression on CD3(+)CD8(+) T cells.

CONCLUSION

Allergen-specific induction of cytokines and chemokines in PBMC and chemokine receptor expression on circulating T cells may contribute to the pathogenesis of NRL allergy.

Latex allergy: low prevalence of immunoglobulin E to highly purified proteins Hev b 2 and Hev b 13

BACKGROUND

Hevea brasiliensis (Hev b) 2 and Hev b 13 have recently been identified as major latex allergens by detecting specific IgE antibodies in >50% of sera from Hev b latex-allergic individuals.

OBJECTIVE

We assessed the prevalence rates for sensitization to extensively purified latex allergens in patients from three diverse geographical areas.

METHODS

Native Hev b 2, Hev b 5, Hev b 6.01 and Hev b 13 were purified by non-denaturating chromatography and were used in ELISAs to assess sera from 215 latex-allergic patients and 172 atopic non-sensitized controls from Finland, Spain and the United States to detect allergen-specific IgE antibodies.

RESULTS

Unexpectedly, even highly purified Hev b 13 contained epitope(s) to which Hev b 6-specific human IgE antibodies bound effectively. Further purification, however, reduced the prevalence of IgE antibody reactivity to low levels: 15%, 5% and 11% for Hev b 2, and 18%, 30% and 27% for Hev b 13 among latex-allergic Finnish, Spanish and American patients, respectively. Interestingly, Finnish patients had a lower prevalence of Hev b 5-specific IgE antibody (28%) as compared with Spanish (49%) and American (71%) patients. The prevalence of Hev b 6.01-specific IgE reactivity was uniformly >50% in all three populations.

CONCLUSION

Neither Hev b 2 nor Hev b 13 appear to be major latex allergens when evaluated in serological assays using highly purified allergens. The reason(s) for the observed differences in published sensitization rates in various geographic regions requires further study. The purity of the allergen preparations has a marked impact on the accuracy of latex-specific IgE antibody detection in epidemiological studies and in the serological diagnosis of latex allergy.

Latex allergy: the sum quantity of four major allergens shows the allergenic potential of medical gloves

BACKGROUND

Assessment of allergenic potential of medical devices made of natural rubber latex (NRL) requires the measurement of concentrations of specific allergenic proteins or polypeptides eluting from rubber.

METHODS

Four NRL allergens (Hev b 1, 3, 5, and 6.02) were quantified in all medical glove brands marketed in Finland in 1999, 2001, and 2003 (n = 208) by a capture enzyme immunoassay. The results were compared with those obtained from previous nationwide market surveys, using a skin prick test-validated human IgE-based ELISA-inhibition method.

RESULTS

A high overall correlation (r = 0.87, 95% CI 0.83-0.90) emerged between the sum values of the four allergens(microg/g glove) and IgE-ELISA inhibition (allergen units, AU/ml, 1 : 5 diluted glove extract). The sum of four allergens when set at 0.15 microg/g discriminated 'low allergenic' (<10 AU/ml) from 'moderate- to high-allergenic' (>/=10 AU/ml) gloves at a sensitivity of 0.93 (95% CI 0.85-0.98) and specificity of 0.90 (95% CI 0.83-0.94). When the sum was below the detection limit (0.03 microg/g) all gloves belonged to the previously defined low-allergen category.

CONCLUSIONS

By comparing the sum concentration of four selected NRL allergens with results obtained in human IgE-ELISA inhibition, it was possible set a cut-off level (0.15 microg/g) below which virtually all gloves contain low or insignificant amounts of allergens, and can be considered as low allergenic. At different cut-off-points, one could calculate the likelihood of a given glove to belong to the previously defined low, moderate or high allergen categories.

Vipera lebetina venom contains all types of snake venom metalloproteases

Snake venoms contain four classes of metalloproteases that all have a typical zinc-chelating sequence (HEXXHGXXH). N-terminal sequences and internal sequences of different purified metalloproteases were determined using Edman sequencing and LC MS/MS technique. Oligonucleotides were designed and used as primers for cDNA cloning from Vipera lebetina venom gland cDNA library. We found that isoforms of fibrinolytic enzyme lebetase Le-4 and Le-3 are synthesized in different way: Le-4 is synthesized as P-I type metalloprotease, Le-3 is synthesized with disintegrin-like domain as P-II type protease and processed post-translationally. An endothelial cell apoptosis-inducing heterodimeric glycosylated metalloprotease, V. lebetina apoptosis-inducing protease (VLAIP), belongs to P-III type containing metalloprotease, disintegrin-like and cysteine-rich domains. All these enzymes hydrolyze the Aalpha-chain and more slowly the Bbeta-chain of fibrinogen. Treatment of HUVEC cells with VLAIP induces changes in the attachment of cells to the substrate and causes apoptosis. V. lebetina venom contains also P-IV type-specific coagulant factor X activator (VLFXA) that cleaves the Arg52-Ile53 bond in the heavy chain of human factor X. VLFXA is a glycoprotein composed of a heavy chain and two C-type lectin-like light chains linked by disulfide bonds. The heavy and light chains of VLFXA are synthesized from different genes.

Differential Susceptibility of Transferrin Glycoforms to Chymotrypsin: A Proteomics Approach to the Detection of Carbohydrate-Deficient Transferrin

Transferrin exhibits heterogeneity in glycosylation characteristic of pathological changes in alcohol abuse and congenital disorders in glycosylation. This study investigated an alternative approach in the detection of carbohydrate-deficient transferrin based on the premise that glycosylation may afford some degree of protection to proteolytic action. Differential susceptibility to proteolysis by chymotrypsin was demonstrated for normal glycosylated and nonglycosylated recombinant human transferrin, using reverse-phase (RP) HPLC, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and LC-tandem mass spectrometry (MS/MS). Peptide fragmentation profiles were consistent with a predominantly high-specificity cleavage pattern of chymotrypsin. The observed peptide fragmentation profile showed that the C-lobe of recombinant full-length nonglycosylated transferrin (rhTf-NG) appeared to be preferentially cleaved, while cleavage of the N-lobe was restricted to the N-terminal and link sequence regions. Although chymotryptic cleavage sites abound in the N-lobe, their resistance to cleavage was independent of glycosylation. Compared to previous studies of lactoferrin, our data suggest disparity in the role by which glycosylation exerts a protective effect in the siderophilin family. It was clear from the transferrin digestions analyzed by HPLC that N-linked glycosylation did confer protection from proteolysis by chymotrypsin. After fragmentation, a range of peptides representing previously cryptic epitopes were identified as potential candidates for an immunological approach to differentiate between the different transferrin glycoforms. Based on its proximity to the Asn413 glycosylation site, a 15-mer peptide, m/z 1690.472 (NKSDNCEDTPEAGYF), was identified as a suitable candidate for raising anti-peptide antibodies for subsequent immunological detection. This novel approach could form the basis for an alternative assay or reference method for the detection of carbohydrate-deficient transferrin.

Enzyme-aided modification of chicken-breast myofibril proteins: effect of laccase and transglutaminase on gelation and thermal stability

The effect of laccase and transglutaminase (TG) on cross-linking, gelation, and thermal stability of salt-soluble chicken-breast myofibril proteins was investigated at pH 6. Both enzymes modified the protein pattern detected by SDS-PAGE. Identification of proteins by peptide mass mapping showed that myosin heavy chain (MHC) and troponin T were the most affected proteins. These proteins faded or disappeared as a function of the incubation time with both enzymes on SDS-PAGE. The molecular weight of actin was not, however, affected by either enzyme. The effects that the enzymes had on the gel formation of chicken-breast myofibrils were studied in 0.35 and 0.60 M NaCl solutions at 3% protein content and a constant temperature of 40 degrees C by using a small deformation viscoelastic measurement. TG substantially increased the storage modulus (G') of 3% protein in 0.35 M NaCl. Without the enzymes, gelation was insignificant in 0.35 M NaCl. The increased solubility of the proteins at 0.60 M NaCl intensified gelation with TG. G' increased 32 and 64% at dosages of 10 and 100 nkat of TG, respectively. Also, laccase increased G' of the gel in 0.60 M salt concentration. However, a high laccase dosage decreased the magnitude of G' below the control level. Differential scanning calorimetric (DSC) measurements indicated slightly reduced myosin heat stability after TG pretreatment and increased actin heat stability with both enzymes. Maximum transition temperatures did not alter with either enzyme.

Cloning of a gluconate/polyol dehydrogenase gene from Gluconobacter suboxydans IFO 12528, characterisation of the enzyme and its use for the production of 5-ketogluconate in a recombinant Escherichia coli strain

A 5-ketogluconate (5-KGA)-forming membrane quinoprotein, gluconate dehydrogenase, was isolated from Gluconobacter suboxydans strain IFO 12528 and partially sequenced. Partial sequences of five internal tryptic peptides were elucidated by mass spectrometry and used to isolate the two adjacent genes encoding the enzyme (EBI accession no. AJ577472). These genes share close homology with sorbitol dehydrogenase from another strain of G. suboxydans (IFO 3255). Substrate specificity of gluconate 5-dehydrogenase (GA 5-DH) turned out to be quite broad, covering many polyols, amino derivatives of carbohydrates, and simple secondary alcohols. There is a broad correlation between the substrate specificity of GA 5-DH and the empirical Bertrand-Hudson rule that predicts the specificity of oxidation of polyols by acetic acid bacteria. Escherichia coli transformed with the genes encoding gluconate dehydrogenase were able to convert gluconic acid into 5-KGA at 75% yield. Furthermore, it was found that 5-KGA can be converted into tartaric acid semialdehyde by a transketolase. These results provide a basis for designing a direct fermentation-based process for conversion of glucose into tartaric acid.

Phthalic anhydride allergy: development and characterization of optimized hapten-carrier conjugates for improved diagnosis

BACKGROUND

At present the diagnosis of IgE-mediated hypersensitivity to phthalic anhydride (PA) is based on conjugates that are not characterized or standardized. The aim of this study was to develop optimized and molecularly characterized PA conjugates that can be used to improve the diagnosis of PA-allergy.

METHODS

The PA conjugates were synthesized and the number of haptens bound on a carrier protein was estimated by matrix-assisted laser desorption/ionization time of light (MALDI-TOF) mass spectrometry. The ability of conjugates to bind IgE and IgG antibodies was measured by enzyme-linked immunosorbent assay (ELISA). Reactivity of the conjugates in vivo was evaluated by skin prick testing.

RESULTS

The most active IgE-binding conjugates had a PA : HSA molar ratio of 80 : 1. In the optimal conjugates the average numbers of PA haptens per carrier molecule of human serum albumin (HSA) were 14-16. In ELISA, all 13 patients and none of the 20 controls had IgE antibodies to optimized PA conjugate. The sensitivity and specificity of the ELISA was comparable to commercial CAP RAST. PA conjugates elicited positive test results in skin prick testing showing that conjugates are immunologically active also in vivo.

CONCLUSIONS

These results indicate that optimized and molecularly characterized PA-HSA conjugates can be used both in vitro and in vivo assays to improve the diagnosis of PA allergy.

Cloning and expression of a fungal L-arabinitol 4-dehydrogenase gene

L-Arabinitol 4-dehydrogenase (EC ) was purified from the filamentous fungus Trichoderma reesei (Hypocrea jecorina). It is an enzyme in the L-arabinose catabolic pathway of fungi catalyzing the reaction from L-arabinitol to L-xylulose. The amino acid sequence of peptide fragments was determined and used to identify the corresponding gene. We named the gene lad1. It is not constitutively expressed. In a Northern analysis we found it only after growth on L-arabinose. The gene was cloned and overexpressed in Saccharomyces cerevisiae, and the enzyme activity was confirmed in a cell extract. The enzyme consists of 377 amino acids and has a calculated molecular mass of 39,822 Da. It belongs to the family of zinc-binding dehydrogenases and has some amino acid sequence similarity to sorbitol dehydrogenases. It shows activity toward L-arabinitol, adonitol (ribitol), and xylitol with K(m) values of about 40 mM toward L-arabinitol and adonitol and about 180 mM toward xylitol. No activity was observed with D-sorbitol, D-arabinitol, and D-mannitol. NAD is the required cofactor with a K(m) of 180 microM. No activity was observed with NADP.

Wheat omega-5 gliadin is a major allergen in children with immediate allergy to ingested wheat

BACKGROUND

Sensitization to wheat by ingestion can lead to food allergy symptoms and wheat-dependent, exercise-induced anaphylaxis. Sensitization by inhalation causes bakers' asthma and rhinitis. Wheat allergens have been characterized at the molecular level in bakers' asthma and in wheat-dependent, exercise-induced anaphylaxis, in which omega-5 gliadin (Tri a 19) is a major allergen. However, little information is available regarding allergens responsible for hypersensitivity reactions to ingested wheat in children.

OBJECTIVE

The aim of this study was to examine whether children with allergy to ingested wheat have IgE antibodies to omega-5 gliadin.

METHODS

Sera were obtained from 40 children (mean age, 2.5 years; range, 0.7-8.2 years) with suspected wheat allergy who presented with atopic dermatitis and/or gastrointestinal and/or respiratory symptoms. Wheat allergy was diagnosed with open or double-blinded, placebo-controlled oral wheat challenge. Wheat omega-5 gliadin was purified by reversed-phase chromatography, and serum IgE antibodies to omega-5 gliadin were measured by means of ELISA. In vivo reactivity was studied by skin prick testing. Control sera were obtained from 22 children with no evidence of food allergies.

RESULTS

In oral wheat challenge, 19 children (48%) reacted with immediate and 8 children (20%) with delayed hypersensitivity symptoms. Sixteen (84%) of the children with immediate symptoms had IgE antibodies to purified omega-5 gliadin in ELISA. In contrast, IgE antibodies to omega-5 gliadin were not detected in any of the children with delayed or negative challenge test results or in the control children. The diagnostic specificity and positive predictive value of omega-5 gliadin ELISA were each 100% for immediate challenge reactions. Skin prick testing with omega-5 gliadin was positive in 6 of 7 children with immediate challenge symptoms and negative in 2 children with delayed challenge symptoms.

CONCLUSION

The results of this study show that omega-5 gliadin is a significant allergen in young children with immediate allergic reactions to ingested wheat. IgE testing with omega-5 gliadin could be used to reduce the need for oral wheat challenges in children.

Increased levels of IgA antibodies against desmin in children with coeliac disease

BACKGROUND

In addition to IgA anti-endomysial antibodies, IgA anti-smooth muscle antibodies have been observed in a number of patients with coeliac disease (CoD), but only limited data exist on the frequency and antigen specificity of IgA against cytoskeletal proteins in CoD.

METHODS

We evaluated the sera of 42 untreated CoD patients, follow-up sera of 26 CoD patients after treatment, and 116 control sera for IgA reactivity to cytoskeletal proteins from the human umbilical cord (HUC) by immunoblotting, and compared the results with anti-tissue transglutaminase IgA (anti-tTG IgA) ELISA and immunofluorescence results.

RESULTS

Serum IgA from CoD patients most frequently recognized a 57-kD antigen in HUC cytoskeletal extract, identified as desmin using mass spectrometry and internal peptide sequencing. Increased IgA reactivity to the human desmin band was detected in 22 children with untreated CoD (52.4%), in 4 treated CoD patients (15.4%), and in 12 control subjects (10.3%) (p < 0.01); similar results were obtained with anti-chicken desmin IgA ELISA. Anti-tTG IgA levels (increased in 71.4% of untreated CoD patients) correlated significantly with anti-desmin IgA levels in untreated CoD, and both autoantibody reactivities decreased in response to a gluten-free diet. Pre-adsorption experiments and affinity purification of anti-desmin IgA antibodies further confirmed that desmin is an IgA autoantigen in CoD and is recognized by antibodies which are not cross-reactive with tTG.

CONCLUSIONS

Anti-desmin IgA antibodies are frequently occurring if not the predominant cytoskeletal antibodies in children with untreated CoD and could be related to the disease process in the small intestine.

Positive skin and oral challenge responses to potato and occurrence of immunoglobulin E antibodies to patatin (Sol t 1) in infants with atopic dermatitis

The clinical significance and molecular specificity of hypersensitivity reactions to raw and cooked potatoes remain ambiguous. We therefore investigated the clinical hypersensitivity to raw and cooked potato in infants suspected to have potato allergy and compared the findings with the occurrence of immunoglobulin E (IgE) antibodies to patatin (Sol t 1), characterized as the primary allergen of potato. Twelve infants (10 to 24 months of age) suffering from atopic dermatitis (AD) and suspected to have adverse reactions to potato, were examined. As a skin exposure test we used rubbing with both raw and cooked potato, and used open oral challenge with cooked potato for 7 days. A special eczema scoring system (SCORAD) was used to assess the severity of symptoms and signs of AD. Skin-prick tests (SPTs) were performed with raw potato and natural Sol t 1, and serological studies included measurement of total serum IgE and IgE antibodies to Sol t 1, and potato radioallergosorbent testing (RAST). The skin-rubbing test with raw potato was positive in seven (58%) and the oral challenge positive in eight (67%) infants. One infant presented with an immediate reaction and seven with a delayed reaction, i.e. exacerbation of AD, after oral challenge responses to cooked potato. Nine (75%) infants had IgE antibodies to Sol t 1 in enzyme-linked immunosorbent assay (ELISA), and SPT to natural Sol t 1 was positive in six (50%) potato-allergic infants. In conclusion, we observed positive challenge responses to both raw and cooked potato in food-allergic atopic infants. The presence of IgE antibodies and concomitant positive SPTs to the heat-stable potato allergen, Sol t 1, suggest that cooked potato can be an allergenic food for infants suffering from AD.

An alpha-L-fucosidase from Thermus sp. with unusually broad specificity

An alpha-L-fucosidase (E.C. 3.2.1.51) exhibiting a wide aglycon specificity expressed in ability of cleaving alpha1 --> 6-, alpha1 -->3-, alpha1 --> 4-, and alpha1 --> 2-O-fucosyl bonds in fucosylated oligosaccharides, has been isolated from culture filtrate of Thermus sp. strain Y5. The alpha-L-fucosidase hydrolyzes p-nitrophenyl alpha-L-fucopyranoside with V(max) of 12.0 +/- 0.1 microM/min/mg and K(m) = 0.20 +/- 0.05 mM and is able to cleave off about 90% of total L-fucose from pronase-treated fractions of fucosyl-containing glycoproteins and about 30% from the native glycoproteins. The purified enzyme is a tetramer with a molecular mass of 240 +/- 10 kDa consisting of four identical subunits with a molecular mass of 61.0 +/- 0.5 kDa. The N-terminal sequence showed homology to some alpha-L-fucosidases from microbial and plant sources. Hydrolysis of p-nitrophenyl alpha-L-fucopyranoside occurs with retention of the anomeric configuration. Transglycosylating activity of the alpha-L-fucosidase was demonstrated in reactions with such acceptors as alcohols, N-acetylglucosamine and N-acetylgalactosamine while no transglycosylation products were observed in the reaction with p-nitrophenyl alpha-L-fucopyranoside. The enzyme can be classified in glycosyl hydrolase family 29.

matB, a common fimbrillin gene of Escherichia coli, expressed in a genetically conserved, virulent clonal group

A novel fimbrial type in Escherichia coli was identified and characterized. The expression of the fimbria was associated with the O18acK1H7 clonal group of E. coli, which cause newborn meningitis and septicemia when grown at low temperature; hence, it was named the Mat (meningitis associated and temperature regulated) fimbria. The fimbriae were purified from a fimA::cat sfaA::Gm fliC::St derivative of the O18K1H7 isolate E. coli IHE 3034. The purified Mat fimbrillin had an apparent molecular mass of 18 kDa and did not serologically cross-react with the type 1 or S fimbria of the same strain. The matB gene encoding the major fimbrillin was cloned from the genomic DNA of the fimA::cat sfaA::Gm fliC::St derivative of IHE 3034. The predicted MatB sequence was of 195 amino acids, contained a signal sequence of 22 residues, and did not show significant homology to any of the previously characterized fimbrial proteins. The DNA sequence of matB was 97.8% identical to a region from nucleotides 17882 to 18469 in the 6- to 8-min region of the E. coli K-12 chromosome, reported to encode a hypothetical protein. The 7-kb DNA fragment containing matB of IHE 3034 was found by restriction mapping and partial DNA sequencing to be highly similar to the corresponding region in the K-12 chromosome. Trans complementation of the matB::cat mutation in the IHE 3034 chromosome showed that matB in combination with matA or matC restored surface expression of the Mat fimbria. A total of 27 isolates representing K-12 strains and the major pathogroups of E. coli were analyzed for the presence of a matB homolog as well as for expression of the Mat fimbria. A conserved matB homolog was found in 25 isolates; however, expression of the Mat fimbriae was detected only in the O18acK1H7 isolates. Expression of the Mat fimbria was temperature regulated, with no or a very small amount of fimbriae or intracellular MatB fimbrillin being detected in cells cultivated at 37(o)C. Reverse transcriptase PCR and complementation assays with mat genes controlled by the inducible trc promoter indicated that regulation of Mat fimbria expression involved both transcriptional and posttranscriptional events.

Glycosylation analysis of two cysteine proteinase inhibitors from Atlantic salmon skin: di-O-acetylated sialic acids are the major sialic acid species on N-glycans

We have recently identified two novel cysteine proteinase inhibitors from the skin of Atlantic salmon (Salmo salar L.), named salmon kininogen and salarin. In preliminary experiments, the proteins were found to be both N- as well as O-glycosylated. In the present study we show that both proteins carry biantennary alpha2,3-sialylated N-glycans. A very high amount of O-acetylated Neu5Ac units are present in the N-glycans, comprising about 60% di-O-acetylated species. Non-O-acetylated Neu5Ac make up less than 5% of the sialic acids in the N-glycans. A small number of Neu5Acalpha2-8Neu5Ac structures were observed in the N-glycans as well. O-glycans from both proteins were recovered by reductive beta-elimination and were identified by mass spectrometric methods as mono- and disialylated core type 1 tri- and tetrasaccharides. The method used for O-glycan isolation prevented the identification of possible O-acetylation in the O-glycan-bound sialic acids, but O-acetylation was observed in one O-glycosylated peptide isolated from trypsin digest of salarin. The chemical nature of the sialic acid modifications was further studied by liquid chromatography tandem mass spectrometry of 1,2-diamino-4,5-methylenedioxybenzene-derivatized sialic acids, revealing 7-, 8-, and 9- but no 4-O-acetylation. To our knowledge, these are the first observations of sialic acid O-acetylation in N-glycans on fish species and represent clearly the most extensive N-glycan O-acetylation described on any species.

Identification of four novel potato (Solanum tuberosum) allergens belonging to the family of soybean trypsin inhibitors

BACKGROUND

We have previously identified patatin (Sol t 1) of potato tubers as a major food allergen among atopic children. In addition to Sol t 1, concomitant IgE binding to other, then unidentified, potato proteins was observed.

METHODS

Purification and identification of the putative allergens were done by both standard and advanced methods of protein chemistry. The patient series comprised 39 children with positive skin prick test (SPT) to raw potato. Immunoblotting and ELISA were used to examine IgE-binding ability and skin prick testing to assess in vivo reactivity of the purified potato proteins.

RESULTS

Four IgE-binding potato proteins with molecular masses ranging from 16 to 20 kDa were purified and identified as cathepsin D-, cysteine-, and aspartic protease inhibitors belonging to the family of soybean trypsin inhibitors (Kunitz type). The proteins were designated Sol t 2, Sol t 3.0101, Sol t 3.0102, and Sol t 4. In ELISA, 51% of the sera of the 39 atopic children showed specific IgE to Sol t 2, 43% to Sol t 3.0101, 58% to Sol t 3.0102, and 67% to Sol t 4, respectively. All these four allergens were able to produce positive wheal-and-flare responses in SPT.

CONCLUSION

In addition to Sol t 1, potato tubers contain several proteins belonging to the family of soybean trypsin inhibitors against which atopic children with positive SPT responses to raw potato have in vitro and in vivo reactive IgE antibodies.

Protein regions important for plasminogen activation and inactivation of alpha2-antiplasmin in the surface protease Pla of Yersinia pestis

The plasminogen activator, surface protease Pla, of the plague bacterium Yersinia pestis is an important virulence factor that enables the spread of Y. pestis from subcutaneous sites into circulation. Pla-expressing Y. pestis and recombinant Escherichia coli formed active plasmin in the presence of the major human plasmin inhibitor, alpha2-antiplasmin, and the bacteria were found to inactivate alpha2-antiplasmin. In contrast, only poor plasminogen activation and no cleavage of alpha2-antiplasmin was observed with recombinant bacteria expressing the homologous gene ompT from E. coli. A beta-barrel topology model for Pla and OmpT predicted 10 transmembrane beta-strands and five surface-exposed loops L1-L5. Hybrid Pla-OmpT proteins were created by substituting each of the loops between Pla and OmpT. Analysis of the hybrid molecules suggested a critical role of L3 and L4 in the substrate specificity of Pla towards plasminogen and alpha2-antiplasmin. Substitution analysis at 25 surface-located residues showed the importance of the conserved residues H101, H208, D84, D86, D206 and S99 for the proteolytic activity of Pla-expressing recombinant E. coli. The mature alpha-Pla of 292 amino acids was processed into beta-Pla by an autoprocessing cleavage at residue K262, and residues important for the self-recognition of Pla were identified. Prevention of autoprocessing of Pla, however, had no detectable effect on plasminogen activation or cleavage of alpha2-antiplasmin. Cleavage of alpha2-antiplasmin and plasminogen activation were influenced by residue R211 in L4 as well as by unidentified residues in L3. OmpT, which is not associated with invasive bacterial disease, was converted into a Pla-like protease by deleting residues D214 and P215, by substituting residue K217 for R217 in L4 of OmpT and also by substituting the entire L3 with that from Pla. This simple modification of the surface loops and the substrate specificity of OmpT exemplifies the evolution of a housekeeping protein into a virulence factor by subtle mutations at critical protein regions. We propose that inactivation of alpha2-antiplasmin by Pla of Y. pestis promotes uncontrolled proteolysis and contributes to the invasive character of plague.

Crystal structure of Streptococcus mutans pyrophosphatase: a new fold for an old mechanism

BACKGROUND

Streptococcus mutans pyrophosphatase (Sm-PPase) is a member of a relatively uncommon but widely dispersed sequence family (family II) of inorganic pyrophosphatases. A structure will answer two main questions: is it structurally similar to the family I PPases, and is the mechanism similar?

RESULTS

The first family II PPase structure, that of homodimeric Sm-PPase complexed with metal and sulfate ions, has been solved by X-ray crystallography at 2.2 A resolution. The tertiary fold of Sm-PPase consists of a 189 residue alpha/beta N-terminal domain and a 114 residue mixed beta sheet C-terminal domain and bears no resemblance to family I PPase, even though the arrangement of active site ligands and the residues that bind them shows significant similarity. The preference for Mn2+ over Mg2+ in family II PPases is explained by the histidine ligands and bidentate carboxylate coordination. The active site is located at the domain interface. The C-terminal domain is hinged to the N-terminal domain and exists in both closed and open conformations.

CONCLUSIONS

The active site similiarities, including a water coordinated to two metal ions, suggest that the family II PPase mechanism is "analogous" (not "homologous") to that of family I PPases. This is a remarkable example of convergent evolution. The large change in C-terminal conformation suggests that domain closure might be the mechanism by which Sm-PPase achieves specificity for pyrophosphate over other polyphosphates.

Rye gamma-70 and gamma-35 secalins and barley gamma-3 hordein cross-react with omega-5 gliadin, a major allergen in wheat-dependent, exercise-induced anaphylaxis

Patients with wheat-dependent, exercise-induced anaphylaxis experience severe allergic reactions when exercising after ingestion of wheat. The major wheat allergen associated with these reactions is a omega-5 gliadin, and patients following a gluten-free diet have remained free of symptoms. The aim of this study was to examine whether allergens cross-reacting with wheat omega-5 gliadin are present in rye, barley and oats. Sera from 23 adult patients with wheat-dependent, exercise-induced anaphylaxis were examined. Cereal allergens cross-reacting with wheat omega-5 gliadin were identified by immunoblot inhibition. The cross-reactive allergens were purified by gel filtration and reversed-phase chromatography and submitted to amino acid sequencing. Cross-reactivity was further studied by IgE ELISA and ELISA inhibition, and in vivo reactivity by skin prick testing. In immunoblotting rabbit anti-omega-5 gliadin antibodies bound to 70 kDa and 32 kDa proteins in rye and a 34-kDa protein in barley, but not to proteins in oats. N-terminal sequencing identified these proteins as rye gamma-70 secalin, rye gamma- 35 secalin and barley gamma-3 hordein, correspondingly. In ELISA 21/23 (91%) patients with wheat-dependent, exercise-induced anaphylaxis showed IgE antibodies to purified gamma-70 secalin, 19/23 (83%) to gamma-35 secalin and 21/23 (91%) to gamma-3 hordein. In ELISA inhibition omega-5 gliadin inhibited over 90% of the IgE binding of pooled patient sera to solid-phase gamma-secalins and gamma-3 hordein. Skin prick testing gave positive reactions to gamma-70 secalin in 10/15 (67%) patients, to gamma-35 secalin in 3/15 (20%) patients and to gamma-3 hordein in 7/15 (47%) patients. The results of this study show that gamma-70 and gamma-35 secalins in rye and gamma-3 hordein in barley cross-react with omega-5 gliadin, a major allergen in wheat-dependent, exercise-induced anaphylaxis. These findings suggest that also rye and barley may elicit symptoms in patients with wheat-dependent, exercise-induced anaphylaxis.

Characteristics and N-terminal amino acid sequence of manganese peroxidase from solid substrate cultures of Agaricus bisporus

Extracellular manganese peroxidase (MnP) was purified from the compost extract of Agaricus bisporus using anion exchange chromatography, gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Two forms (MnP1 and MnP2) were separated by isoelectric focusing and their isoelectric points were determined to be 3.25 (MnP1) and 3.3 (MnP2). Both forms had a molecular mass of 40 kDa. The first 25 amino acids of the N-terminal end of MnP1 sequence was found to share 68% identity with a Pleurotus ostreatus and a P. eryngii MnP. Lignin peroxidase was not detected during any of the steps in the purification process. In liquid cultures with both soluble and insoluble carbon sources in defined medium (D-glucose, glycerol, Whatman CC-41 microcrystalline cellulose or Solka-floc cellulose) MnP protein was detected in culture fluid by Western blot, but no MnP activity could be detected. A. bisporus appears to be in the group of ligninolytic fungi which do not produce lignin peroxidase.

Scots pine expresses short-root-specific peroxidases during development

Nine short-root-specific proteins from Scots pine (Pinus sylvestris L.) detected and isolated as individual spots by 2D-PAGE were identified. The similar peptide mass maps obtained for all nine polypeptide spots together with lectin-blotting results suggest that they represent forms of the same modified protein. N-Terminal sequence analysis of two of the peptides showed high similarity to peroxidases. RT-PCR with oligonucleotide primers corresponding to determined peptide sequences and conserved regions in plant peroxidases led to isolation of Psyp1 cDNA which is most abundantly expressed in short roots. Psyp1 is the first peroxidase cDNA to be isolated from the genus Pinus. It encodes a 363-amino-acid class-III peroxidase with a calculated molecular mass of 35.7 kDa and theoretical pI of 4.74. The predicted PSYP1 amino-acid sequence is grouped with other class-III peroxidases in phylogenetic analyses, but it has a unique amino-acid sequence which may be associated with its function in short roots or with its phylogenetic group. The presence of a signal sequence for extracellular transport indicates that PSYP1 belongs to the group of secreted class-III peroxidases. The presence of 10 tyrosine residues and putative auxin-binding regions in PSYP1 suggests that the function of the enzyme is associated with cell-wall formation in short roots. The downregulation of Psyp1 expression in symbiotic short roots hosting the ectomycorrhizal fungus Suillus bovinus is perhaps related to the change in cell-wall structure necessary for ectomycorrhizal development.

Use of matrix-assisted laser desorption/ionization time-of-flight mass mapping and nanospray liquid chromatography/electrospray ionization tandem mass spectrometry sequence tag analysis for high sensitivity identification of yeast proteins separated by two-dimensional gel electrophoresis

Current analytical techniques in protein identification by mass spectrometry are based on the generation of peptide mass maps or sequence tags that are idiotypic for the protein sequence. This work reports on the development of the use of mass spectrometric methods for protein identification in research on metabolic pathways of a genetically modified strain of the baker's yeast Saccharomyces cerevisiae. This study describes the use of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass mapping and liquid chromatography/quadrupole time-of-flight electrospray ionization tandem mass spectrometry (LC/Q-TOF-ESI-MS/MS) sequence tag analysis in identification of yeast proteins separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). The spots were selected for analysis in order to collect information for future studies, to cover the whole pI range from 3 to 10, and to evaluate information from spots of different intensities. Mass mapping as a rapid, high-throughput method was in most cases sensitive enough for identification. LC/MS/MS was found to be more sensitive and to provide more accurate data, and was very useful when analyzing small amounts of sample. Even one sequence tag acquired by this method could be enough for unambiguous identification, and, in the present case, successfully identified a point mutation.

The gaf fimbrial gene cluster of Escherichia coli expresses a full-size and a truncated soluble adhesin protein

The GafD lectin of the G (F17) fimbriae of diarrhea-associated Escherichia coli was overexpressed and purified from the periplasm of E. coli by affinity chromatography on GlcNAc-agarose. The predicted mature GafD peptide comprises 321 amino acids, but the predominant form of GafD recovered from the periplasm was 19,092 Da in size and corresponded to the 178 N-terminal amino acid residues, as judged by mass spectrometry and amino acid sequencing, and was named DeltaGafD. Expression of gafD from the cloned gaf gene cluster in DegP-, Lon-, and OmpT-deficient recombinant strains did not significantly decrease the formation of DeltaGafD. The peptide was also detected in the periplasm of the wild-type E. coli strain from which the gaf gene cluster originally was cloned. We expressed gafD fragments encoding C-terminally truncated peptides. Peptides GafD1-252, GafD1-224, GafD1-189, and the GafD1-178, isolated from the periplasm by affinity chromatography, had apparent sizes closely similar to that of DeltaGafD. Only trace amounts of truncated forms with expected molecular sizes were detected in spheroplasts. In contrast, the shorter GafD1-157 peptide was detected in spheroplasts but not in the periplasm, indicating that it was poorly translocated or was degraded by periplasmic proteases. Pulse-chase assays using gafD indicated that DeltaGafD was processed from GafD and is not a primary translation product. The DeltaGafD peptide was soluble by biochemical criteria and exhibited specific binding to GlcNAc-agarose. Inhibition assays with mono- and oligosaccharides gave a similar inhibition pattern in the hemagglutination by the G-fimbria-expressing recombinant E. coli strain and in the binding of [(14)C]DeltaGafD to GlcNAc-agarose. DeltaGafD bound specifically to laminin, a previously described tissue target for the G fimbria. Our results show that a soluble, protease-resistant subdomain of GafD exhibits receptor-binding specificity similar to that for intact G fimbriae and that it is formed when gafD is expressed alone or from the gaf gene cluster.

Characterization of the collagen-binding S-layer protein CbsA of Lactobacillus crispatus

The cbsA gene of Lactobacillus crispatus strain JCM 5810, encoding a protein that mediates adhesiveness to collagens, was characterized and expressed in Escherichia coli. The cbsA open reading frame encoded a signal sequence of 30 amino acids and a mature polypeptide of 410 amino acids with typical features of a bacterial S-layer protein. The cbsA gene product was expressed as a His tag fusion protein, purified by affinity chromatography, and shown to bind solubilized as well as immobilized type I and IV collagens. Three other Lactobacillus S-layer proteins, SlpA, CbsB, and SlpnB, bound collagens only weakly, and sequence comparisons of CbsA with these S-layer proteins were used to select sites in cbsA where deletions and mutations were introduced. In addition, hybrid S-layer proteins that contained the N or the C terminus from CbsA, SlpA, or SlpnB as well as N- and C-terminally truncated peptides from CbsA were constructed by gene fusion. Analysis of these molecules revealed the major collagen-binding region within the N-terminal 287 residues and a weaker type I collagen-binding region in the C terminus of the CbsA molecule. The mutated or hybrid CbsA molecules and peptides that failed to polymerize into a periodic S-layer did not bind collagens, suggesting that the crystal structure with a regular array is optimal for expression of collagen binding by CbsA. Strain JCM 5810 was found to contain another S-layer gene termed cbsB that was 44% identical in sequence to cbsA. RNA analysis showed that cbsA, but not cbsB, was transcribed under laboratory conditions. S-layer-protein-expressing cells of strain JCM 5810 adhered to collagen-containing regions in the chicken colon, suggesting that CbsA-mediated collagen binding represents a true tissue adherence property of L. crispatus.

Identification of foetal brain proteins by two-dimensional gel electrophoresis and mass spectrometry comparison of samples from individuals with or without chromosome 21 trisomy

Protein expression in foetal brain with or without chromosome 21 trisomy (Down's syndrome) was analyzed by two-dimensional gel electrophoresis and mass spectrometry. Data generated by in-gel digestion and matrix-assisted laser desorption/ionization mass spectrometry allowed identification of 40 proteins. Most of these are common to syndrome and healthy subjects and represent different types of protein. However, a few proteins, identified as truncated structural proteins (tubulin, actin), were present in part of the trisomy samples but absent from the controls. This is interpreted to indicate increased proteolysis in the syndrome samples but could also reflect some altered expression or processing. Independent of the apparently increased proteolysis in the syndrome samples, and in spite of the use of total brain tissues, the results show that two-dimensional protein separation patterns are largely similar between the syndrome and control samples upon silver-staining, but that differences associated with structural components can be detected and identified.

In mouse alpha -methylacyl-CoA racemase, the same gene product is simultaneously located in mitochondria and peroxisomes

alpha-Methylacyl-CoA racemase, an enzyme of the bile acid biosynthesis and branched chain fatty acid degradation pathway, was studied at the protein, cDNA, and genomic levels in mouse liver. Immunoelectron microscopy and subcellular fractionation located racemase to mitochondria and peroxisomes. The enzymes were purified from both organelles with immunoaffinity chromatography. The isolated proteins were of the same size, with identical N-terminal amino acid sequences, and the existence of additional proteins with alpha-methylacyl-CoA racemase activity was excluded. A racemase gene of about 15 kilobases was isolated. Southern blot analysis and chromosomal localization showed that only one racemase gene is present, on chromosome 15, region 15B1. The putative initial ATG in the racemase gene was preceded by a functional promotor as shown with the luciferase reporter gene assay. The corresponding cDNAs were isolated from rat and mouse liver. The recombinant rat protein was overexpressed in active form in Pichia pastoris. The presented data suggest that the polypeptide encoded by the racemase gene can alternatively be targeted to peroxisomes or mitochondria without modifications. It is concluded that the noncleavable N-terminal sequence of the polypeptide acts as a weak mitochondrial and that the C-terminal sequence acts as a peroxisomal targeting signal.

Proteome analysis reveals ubiquitin-conjugating enzymes to be a new family of interferon-alpha-regulated genes

Interferon (IFN)-alpha is a cytokine with antiviral, antiproliferative, and immunomodulatory properties, the functions of which are mediated via IFN-induced protein products. We used metabolic labeling and two-dimensional gel electrophoresis followed by MS and database searches to identify potentially new IFN-alpha-induced proteins in human T cells. By this analysis, we showed that IFN-alpha induces the expression of ubiquitin cross-reactive protein (ISG15) and two ubiquitin-conjugating enzymes, UbcH5 and UbcH8. Northern-blot analysis showed that IFN-alpha rapidly enhances mRNA expression of UbcH5, UbcH6 and UbcH8 in T cells. In addition, these genes were induced in macrophages in response to IFN-alpha or IFN-gamma stimulation or influenza A or Sendai virus infections. Similarly, IFNs enhanced UbcH8 mRNA expression in A549 lung epithelial cells, HepG2 hepatoma cells, and NK-92 cells. Cycloheximide, a protein synthesis inhibitor, did not block IFN-induced upregulation of UbcH8 mRNA expression, suggesting that UbcH8 is the primary target gene for IFN-alpha and IFN-gamma. Ubiquitin conjugation is a rate-limiting step in antigen presentation and therefore the upregulation of UbcHs by IFNs may contribute to the enhanced antigen presentation by macrophages. Our results show that proteome analysis of cells is a suitable method for identifying previously unrecognized cytokine-inducible genes.

Molecular epidemiology of coxsackievirus B4 and disclosure of the correct VP1/2A(pro) cleavage site: evidence for high genomic diversity and long-term endemicity of distinct genotypes

Genetic diversity among 107 coxsackievirus B4 field isolates has been studied. These isolates included clinical and environmental isolates originating from Finland, the Netherlands and France, and also from several other countries, including the USA. Three genomic regions were used for phylogenetic analyses: the VP1/2A junction, the entire VP1 and the VP4/VP2 region. Alignment of the deduced amino acid sequence in the VP1/2A junction revealed extensive sequence variation at the previously proposed cleavage site. MS analysis of proteolytic fragments from VP1 revealed that the exact cleavage site is situated between amino acid residues Thr-849 and Gly-850. At least seven distinct genetic lineages, or genotypes, had been circulating in Europe during the period 1959-1998. Two genotypes were endemic in the Netherlands during most of the investigated period. Genetically closely related strains could be found in different countries, and different genotypes co-circulated at the same time in a given country. Clustering patterns were identical in the three genomic intervals. In the VP4/VP2 region, the intraserotypic variation approached interserotype variation. Sequence comparisons of the entire VP1 gene gave a reliable genetic identification of enterovirus serotype. It is suggested that, for genotype classification of previously serotyped coxsackievirus B4 isolates, comparison of VP1/2A sequences is sufficient, but for more detailed investigation of genetic relationships, and for 'genetic serotyping', the entire VP1 gene should be used. The VP4/VP2 region is less reliable for genetic serotyping and genotyping, although the primers are able to amplify many different serotypes.

IgE reactivity to patatin-like latex allergen, Hev b 7, and to patatin of potato tuber, Sol t 1, in adults and children allergic to natural rubber latex

BACKGROUND

Patients allergic to natural rubber latex (NRL) frequently show positive skin prick tests (SPT) and hypersensitivity reactions to various fruits, such as avocado, banana, and kiwi, as well as to vegetables such as potato.

METHODS

Hev b 7 was purified from NRL "C-serum" and Sol t 1 from potato extract, and they were detected by immunoblotting. IgE antibodies to Hev b 7 and Sol t 1 were measured with ELISA in sera from 35 adults and 35 children allergic to NRL. ELISA inhibition and immunoblotting were used to study allergen cross-reactivity. The in vivo reactivity of Hev b 7 and Sol t 1 were demonstrated in the SPT.

RESULTS

Seventeen (49%) of the 35 NRL-allergic adults had IgE antibodies to Hev b 7, in contrast to only one of the 35 NRL-allergic children. Fifteen (43%) of the NRL-allergic adults and 29 (83%) of the NRL-allergic children had IgE antibodies to Sol t 1. Ten (29%) of the adult sera showed IgE binding to both Sol t 1 and Hev b 7, and crosswise inhibition tests with pooled sera revealed marked cross-reactivity. In the SPT, both natural Hev b 7 and Sol t 1 were able to produce a wheal and flare reaction.

CONCLUSIONS

One-half of the NRL-allergic adults, but only one of the NRL-allergic children, had IgE antibodies to natural Hev b 7. These results suggest that Hev b 7 is an important NRL allergen for adults, but not for children. Elucidation of the clinical importance of the observed cross-reactivity between Hev b 7 and Sol t 1 requires further studies.

Endoxylanase II from Trichoderma reesei has several isoforms with different isoelectric points

Two minor xylanases present in Trichoderma reesei Rut C30 cultivation broth were purified as a mixture using ion-exchange, hydrophobic-interaction and gel chromatography. The purified enzyme preparation contained two active xylanases with pI values of 7.1 and 8.1. Both components had a molecular mass of 20 kDa. The purified xylanase preparation exhibited properties very similar to those of the previously isolated XYL II (pI 9.0) of T. reesei Rut C30. The activity and stability properties, apparent kinetic parameters as well as the titration curve forms were similar. The major difference in enzymic properties was the significantly lower specific activity of the pI-7.1+8.1 xylanase mixture (3350 nkat/mg) compared with the specific activity of XYL II (13500 nkat/mg). Amino acid sequences of tryptic peptides (34% of the total amino acid sequence was determined) were identical to the amino acid sequence of XYL II. Furthermore, in vitro modification of the pI-9.0 form of XYL II to pI-8.1 and pI-7.1 forms was demonstrated. Thus the purified xylanase preparation most probably contained two modified forms of XYL II. The primary amino acid sequence of XYL II contains 28 glutamine and asparagine residues and theoretically deamination of one of them lowers the pI to 8.06 and deamination of two amino acids lowers the pI to 7.02.

Atlantic salmon (Salmo salar L.) skin contains a novel kininogen and another cysteine proteinase inhibitor

We describe the purification and characterization of two novel cysteine proteinase inhibitors found in Atlantic salmon skin. One of these, salmon kininogen, has a molecular mass of 52 kDa as determined by matrix-assisted laser desorption/ionization time-of-flight MS, is multiply charged with pI values of 4.0, 4.2 and 4.6 and shows homology to kininogens including the bradykinin motif. The other, salarin, has a molecular weight of 43 kDa, a pI of 5.1 and shows weak homology to cysteine proteinases. Both proteins are N- and O-glycosylated and inhibit papain and ficin but not trypsin.

A novel function for a ubiquitous plant enzyme pectin methylesterase: the host-cell receptor for the tobacco mosaic virus movement protein

Plant virus-encoded movement proteins promote viral spread between plant cells via plasmodesmata. The movement is assumed to require a plasmodesmata targeting signal to interact with still unidentified host factors presumably located on plasmodesmata and cell walls. The present work indicates that a ubiquitous cell wall-associated plant enzyme pectin methylesterase of Nicotiana tabacum L. specifically binds to the movement protein encoded by tobacco mosaic virus. We also show that pectin methylesterase is an RNA binding protein. These data suggest that pectin methylesterase is a host cell receptor involved in cell-to-cell movement of tobacco mosaic virus.

Avidin is a promising tag for fusion proteins produced in baculovirus-infected insect cells

The baculovirus expression vector system (BEVS) has become one of the most versatile and powerful eukaryotic systems for recombinant protein expression. We have constructed a novel baculovirus transfer vector (pbacAVs+C) which allows for the efficient production, detection, and single-step purification of the desired molecule as a secretion-compatible avidin fusion protein in insect cells. It also enables fast construction of the baculoviruses by site-specific transposition in Escherichia coli. To demonstrate the power of this vector, we report here on the production of immunologically intact hevein, a major cysteine-rich latex allergen, as avidin fusion protein. Our results indicate that avidin is a stable and versatile tag in the BEVS. It retains its extraordinarily high biotin-binding activity and also enables independent folding of the fusion partner. The versatility with which avidin fusion proteins can be detected, purified, and immobilized is the basis for the use of our system as a useful alternative in eukaryotic fusion protein production.

Reactions of blue and yellow fungal laccases with lignin model compounds

Laccases of white-rot fungi Panus tigrinus, Phlebia radiata, and Phlebia tremellosa were isolated from cultures grown in liquid media which did not contain lignin and from the cultures grown on wheat straw. The physical and chemical properties of the laccases grown in submerged cultures were typical for blue fungal laccases. The laccases of the same fungi isolated from the solid-state cultures differed from the blue forms by lack of an absorption maximum at 610 nm. The typical blue laccases of P. tigrinus, Ph. radiata, and Ph. tremellosa acquired an ability to oxidize veratryl alcohol and a non-phenolic dimeric lignin model compound of beta-1-type only in the presence of a redox mediator, 2, 2'-azinobis(3-ethylbenzthiazolinesulfonic acid). The P. tigrinus and Ph. radiata yellow laccases catalyzed the oxidation of the same substrates without any mediator. The rate of the reaction of the blue laccases with a phenolic dimeric lignin model compound of beta-O-4-type was higher than that of the yellow laccases. The yellow laccases are apparently formed by the reaction of the blue laccases with low-molecular-weight lignin decomposition products.

Purification and protein composition of PM2, the first lipid-containing bacterial virus to be isolated

The marine, icosahedral bacteriophage PM2 was isolated in the late 1960s. It was the first phage for which lipids were firmly demonstrated to be part of the virion structure and it has been classified as the type organism of the Corticoviridae family. The host, Pseudoalteromonas espejiana BAL-31, belongs to a common group of marine bacteria. We developed a purification method producing virions with specific infectivity approximately as high as that of the lipid-containing phages PRD1 and &phi;6. The sensitivity of the virus to normally used purification media such as those containing sucrose is demonstrated. We also present an alternative host, a pseudoalteromonad, that allows enhanced purification of the virus under reduced salt conditions. We show, using N-terminal amino acid sequencing and comparison with the genomic sequence, that there are at least eight structural proteins in the infectious virus.

Matrix metalloproteinases-3, -7, and -12, but not -9, reduce high density lipoprotein-induced cholesterol efflux from human macrophage foam cells by truncation of the carboxyl terminus of apolipoprotein A-I. Parallel losses of pre-beta particles and the high affinity component of efflux

Matrix metalloproteinases (MMPs) have been suggested to function in remodeling of the arterial wall, but no information is available on their possible role in early atherogenesis, when cholesterol accumulates in the cells of the arterial intima, forming foam cells. Here, we incubated the major component responsible for efflux of cholesterol from foam cells, high density lipoprotein 3 (HDL(3)), with MMP-1, -3, -7, -9, or -12 at 37 degrees C before adding it to cholesterol-loaded human monocyte-derived macrophages. After incubation with MMP-3, -7, or -12, the ability of HDL(3) to induce the high affinity component of cholesterol efflux from the macrophage foam cells was strongly reduced, whereas preincubation with MMP-1 reduced cholesterol efflux only slightly and preincubation with MMP-9 had no effect. These differential effects of the various MMPs were reflected in their differential abilities to degrade the small pre-beta migrating particles present in the HDL(3) fraction. NH(2)-terminal sequence and mass spectrometric analyses of the apolipoprotein (apo) A-I fragments generated by MMPs revealed that those MMPs that strongly reduced cholesterol efflux (MMPs-3, -7, and -12) cleaved the COOH-terminal region of apoA-I and produced a major fragment of about 22 kDa, whereas MMPs-1 and -9, which had little and no effect on cholesterol efflux, degraded apoA-I only slightly and not at all, respectively. These results show, for the first time, that some members of the MMP family can degrade the apoA-I of HDL(3), so blocking cholesterol efflux from macrophage foam cells. This expansion of the substrate repertoire of MMPs to include apoA suggests that these proteinases are directly involved in the accumulation of cholesterol in atherosclerotic lesions.

Increased allergen production in turnip (Brassica rapa) by treatments activating defense mechanisms

BACKGROUND

Practical applications to enhance the productivity of agriculture by using plants with improved resistance to pathogens are expected to increase in the near future. Defense proteins play an important role in pathogen resistance, and some defense-related proteins are significant cross-reacting allergens. For example, cross-allergies are common among patients allergic to natural rubber latex (NRL), which contains many defense-related proteins.

OBJECTIVE

Using a model plant (ie, turnip), we studied whether allergen contents increase after treatments activating defense mechanisms of the plants.

METHODS

Whole or wounded turnips treated with salicylic acid, ethephon, or water were incubated for 2, 4, or 8 days. Allergen content was investigated by IgE immunoblotting with sera from patients allergic to NRL. An induced protein that bound IgE most intensively was purified and further characterized by mass analysis, amino acid sequencing, IgE-ELISA, and skin prick tests.

RESULTS

In immunoblotting, clear IgE-binding bands were discernible only in samples from chemically treated plants. IgE was bound most intensively to a protein with an apparent molecular weight of 25 kd in SDS-PAGE and with a determined molecular weight of 18.7 kd. Sequenced peptides of the 18.7-kd protein showed over 70% homology to prohevein, a major allergen of NRL, and to many other prohevein-like defense proteins. In ELISA, sera from 30 of 34 (88%) adults and 21 of 26 (81%) children previously shown to have IgE against prohevein bound to the purified protein. In skin prick testing with the protein, 4 of 6 patients allergic to NRL had positive reactions.

CONCLUSION

These results demonstrate that activating defense mechanisms of plants may considerably increase their allergen content.

A novel wheat gliadin as a cause of exercise-induced anaphylaxis

BACKGROUND

Food-dependent, exercise-induced anaphylaxis is a severe form of allergy; the reaction is caused by ingestion of a specific food before exercise. This disorder often escapes diagnosis because neither the ingested food nor the exercise alone induces the symptoms.

OBJECTIVE

The aim of the study was to characterize the allergens involved in wheat-dependent, exercise-induced anaphylaxis and to describe the clinical outcome in a series of 18 adult patients.

METHODS

All 18 patients had experienced recurrent episodes of generalized urticaria during exercise, 17 patients in association with collapse and 15 patients with an anaphylactic reaction. The symptoms appeared only when the patients had eaten food containing wheat before exercise. Wheat allergens were detected by immunoblotting, purified by gel filtration and reversed-phase chromatography, and subjected to N-terminal sequencing. The IgE-binding ability of the purified proteins was studied by ELISA, and their in vivo reactivity was studied by skin prick testing.

RESULTS

IgE antibodies from pooled patient sera were bound to 65-kd and 40-kd wheat proteins in immunoblotting. The 65-kd allergen was a previously undescribed wheat protein, showing 61% sequence identity to gamma-gliadin, whereas the 40-kd allergen had 100% identity to alpha-gliadin. In ELISA, all 18 patients showed elevated IgE levels to the novel gamma-like gliadin, and 13 of the patients showed elevated IgE levels to the alpha-gliadin. None of the 54 control subjects with wheat allergy, urticaria, or coeliac disease had IgE antibodies to the gamma-like gliadin. The in vivo reactivity of the gamma-like gliadin was verified by positive skin prick test responses in all of the 15 patients who were tested. During the follow-up on a gluten-free or wheat-free diet, 3 patients experienced reactions after having unknowingly eaten wheat before exercise, but all the other patients who were adhering to the diet remained symptom-free.

CONCLUSION

This study shows that wheat is a frequent cause of food-dependent, exercise-induced anaphylaxis and suggests that the major allergen is a previously undescribed gamma-like gliadin. For screening of this life-threatening allergy, we recommend skin prick testing with crude gliadin and we recommend a gluten-free diet for treatment.

N-glycan structures of matrix metalloproteinase-1 derived from human fibroblasts and from HT-1080 fibrosarcoma cells

Matrix metalloproteinase-1 (MMP-1) is a collagenolytic metalloproteinase capable of cleaving native triple-helical forms of several collagen subtypes, as well as a number of non-collagenous substrates. The role of MMP-1 in various diseases affecting the connective tissue is well characterized. MMP-1 is secreted as both glycosylated and unglycosylated species, and the two forms have been shown to be identical with respect to substrate specificity, specific activity and inhibitory profile. No function for the glycan moiety of the enzyme has been ascribed to date. In the present study, we report on the detailed characterization of MMP-1-derived oligosaccharides. Using strategies based on sequential exoglycosidase digestion combined with matrix-assisted laser desorption ionization-time of flight MS and electrospray tandem MS, we have characterized the N-glycan structures of MMP-1, derived from human dermal fibroblasts and from the HT-1080 fibrosarcoma cell line. MMP-1 derived from fibroblasts was found to carry mainly alpha 2,3-sialylated complex-type diantennary glycans. On the other hand, HT-1080 cells produce MMP-1 that has a heterogeneous glycosylation pattern, comprising diantennary glycans carrying Lewis X, LacdiNAc, sialylated LacdiNAc and GalNAc beta 1,4 (Fuc alpha 1,3)GlcNAc (LacdiNAc analogue of Lewis X) as terminal elements. We also show that, of the two potential glycosylation sites in the MMP-1 sequence, only Asn120 is used.

Analysis of the multimeric state of proteins by matrix assisted laser desorption/ionization mass spectrometry after cross-linking with glutaraldehyde

We have undertaken a systematic study on the suitability of matrix-assisted laser desorption/ionization mass spectrometry to analyze and determine the multimericity of several proteins after cross-linking with glutaraldehyde. Using both commercially available proteins and others of viral origin currently being characterized in our laboratory, we studied the range of concentrations of cross-linker and protein for optimal analysis. Under the conditions developed during this study, we confirmed the multimeric states of three phage PRD1 structural proteins with monomeric masses ranging from 13.5 to 63 kDa. In addition, we addressed the question of the general applicability of the method by using it successfully to confirm the stoichiometry of the heptameric chaperonin GroEL, a bacterial protein with a mass well over 450 kDa.

Identification of patatin as a novel allergen for children with positive skin prick test responses to raw potato

BACKGROUND

Peeling of raw potatoes may cause allergic symptoms, such as sneezing, wheezing, and contact urticaria, for adults. For children, potatoes as food may cause various allergic reactions. However, the identity and molecular structure of the putative allergens in potato have remained unknown.

OBJECTIVE

The aim of our study was to identify possible major allergens in potato by using sera of atopic children suspected of having food allergy and having positive skin prick test responses to raw potato.

METHODS

Potato proteins were purified by standard methods of protein chemistry and characterized with amino-terminal sequencing and mass spectrometry. The IgE-binding ability of the purified proteins was verified by immunoblotting and ELISA with IgE antibodies from the sera of atopic children having positive skin prick test responses to raw potato.

RESULTS

Immunoblotting showed strong IgE binding to a 43-kd protein, identified as patatin, the main storage protein of potato tubers. In ELISA, 20 of 27 (74%) children with positive skin prick test responses to potato and none of the control subjects showed specific binding of IgE antibodies to purified patatin. A positive wheal-and-flare reaction was seen in 8 of 14 children prick tested with purified patatin.

CONCLUSION

These results show that patatin in potatoes is a significant, previously unrecognized,IgE-binding protein for children with a positive skin prick test response to raw potato. Further studies are needed to confirm the clinical importance of potatoes, and especially patatin, as a food allergen.