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PubMed1999

Rubber particles from four different species, examined by transmission electron microscopy and electron-paramagnetic-resonance spin labeling, are found to consist of a homogeneous rubber core enclosed by a contiguous, monolayer biomembrane

The physical characteristics of rubber particles from the four rubber (cis-1,4-polyisoprene) producing species Euphorbia lactiflua Phil., Ficus elastica Roxb., Hevea brasiliensis Mull. Arg., and Parthenium argentatum Gray, were investigated using transmission electron microscopy (TEM) and electron-paramagnetic-resonance (EPR) spin labeling spectroscopy. Transmission electron microscopy showed the rubber particles to be composed of a spherical, homogeneous, core of rubber enclosed by a contiguous, electron-dense, single-track surface layer. The biochemical composition of the surface layer and its single-track TEM suggested that a monolayer biomembrane was the surface structure most compatible with the hydrophobic rubber core. The EPR spectra for a series of positional isomers of doxyl stearic acid, used to label the surface layer of the rubber particles, exhibited flexibility gradients and evidence for lipid-protein interactions for all four rubber particle types that is consistent with a biomembrane-like surface. The EPR spectra confirmed that the surface biomembrane is a monolayer. Thus, rubber particles appear similar to oil bodies in their basic architecture. The EPR spectra also provided information on protein location and degree of biomembrane penetration that correlated with the known properties of the rubber-particle-bound proteins. The monolayer biomembrane serves as an interface between the hydrophobic rubber interior and the aqueous cytosol and prevents aggregation of the particles. An unexpected observation for the probes in pure polyisoprene was evidence of an intrinsic flexibility gradient associated with the stearic acid molecule itself.

Journal Article↗
PubMed2026

Identification and functional analysis of MeJA-responsive bHLH family genes in Taraxacum kok-saghyz.

Taraxacum kok-saghyz (T. kok-saghyz) is considered a highly promising alternative source of natural rubber (NR), as its roots synthesize high-molecular-weight NR comparable to that produced by Hevea brasiliensis. The basic helix-loop-helix (bHLH) family of transcription factors (TFs) plays crucial roles in plant organogenesis, hormonal signal transduction, and the regulation of secondary metabolism. This study aimed to systematically identify TkbHLH family members and to elucidate their potential functions in responding to methyl jasmonate (MeJA) and regulating root development. Based on the T. kok-saghyz genome, 172 TkbHLH members were identified and phylogenetically classified into 16 subfamilies. Among these, 37 genes were selected due to their significant induction by MeJA. Sequence analysis confirmed all encoded proteins contain the conserved bHLH domain. Subcellular localization verified nuclear localization of five core TkbHLH proteins. Interactions were shown by yeast two-hybrid and bimolecular fluorescence complementation, revealing these proteins form homodimers and heterodimers. Notably, a specific interaction was detected between TkbHLH162 and TkHMGS1, a key enzyme in the mevalonate (MVA) pathway, suggesting a potential molecular link between JA signaling and the rubber biosynthesis precursor pathway. Functional characterization via overexpression assays showed that selected TkbHLH genes significantly either promoted or inhibited root elongation. In summary, this study presents the first systematic characterization of the bHLH TF family in T. kok-saghyz, elucidating its involvement in JA signal response, protein interaction networks, and root development regulation. These findings provide a crucial foundation for further investigation into the molecular mechanisms by which TkbHLH TFs influence root morphogenesis and NR biosynthesis in T. kok-saghyz.

Taraxacum kok-saghyz (T. kok-saghyz)↗
PubMed2006

Molecular cloning of a HMG-CoA reductase gene from Eucommia ulmoides Oliver.

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) catalyzes the conversion of HMG-CoA to mevalonate, which is the first committed step in the pathway for isoprenoid biosynthesis in plants. A full-length cDNA encoding HMGR (designated as EuHMGR, GenBank Accession No. AY796343) was isolated from Eucommia ulmoides by rapid amplification of cDNA ends (RACE). The full-length cDNA of EuHMGR comprises 2281 bp with a 1770-bp open reading frame (ORF) encoding a 590-amino-acid polypeptide with two trans-membrane domains revealed by bioinformatic analysis. Molecular modeling showed that EuHMGR is a new HMGR with a spatial structure similar to other plant HMGRs. The deduced protein has an isoelectric point (pI) of 6.89 and a calculated molecular weight of about 63 kDa. Sequence comparison analysis showed that EuHMGR had highest homology to HMGR from Hevea brasiliensis. As expected, phylogenetic tree analysis indicated that EuHMGR belongs to plant HMGR group. Tissue expression pattern analysis showed that EuHMGR is strongly expressed in the leaves and stems whereas it is only poorly expressed in the roots, which implies that EuHMGR may be a constitutively expressing gene. Functional complementation of EuHMGR in HMGR-deficient mutant yeast JRY2394 demonstrated that EuHMGR mediates the mevalonate biosynthesis in yeast.

Amino Acid Motifs↗
PubMed1991

Crystal structure of hevein at 2.8 A resolution.

The three-dimensional structure of hevein, a low molecular weight protein isolated from the latex of Hevea brasiliensis, has been determined by X-ray diffraction at 2.8 A resolution. The protein crystallizes in space group P2(1)2(1)2(1), with lattice constants a = 21.78, b = 31.86, c = 51.12 A. The structure was solved by molecular replacement methods using the domain C of wheat germ agglutinin (WGA) as search model. The positions and individual isotropic temperature factors of the 324 atoms have been refined by the Hendrickson and Konnert restrained refinement procedure. While tight restraints have been maintained on the bonded distances and angles, the R-factor has dropped to 24.1% and an averaged B value of 9.5 A2, using 78% (802) of the total possible number of reflections in the resolution range 5-2.8 A. The tertiary structure is very similar to that of domain C of WGA from residues 3-31.

ABO Blood-Group System↗
PubMed1992

Antifungal activity of chitin-binding PR-4 type proteins from barley grain and stressed leaf.

Antifungal activity in vitro has been associated with barley leaf and grain proteins which are homologous with pathogenesis related proteins of type 4 (PR-4) from tobacco and tomato and with C terminal domains of potato win and Hevea hevein precursor proteins. One protein (pI approximately 9.3, M(r) approximately 13.7 kDa) from barley grain and two very similar proteins from leaves infected with Erysiphe graminis were isolated by chitin affinity chromatography, but none of the proteins showed chitinase activity in vitro. The leaf proteins were increased several fold in response to either Erysiphe infection or NiCl2 infiltration and accumulated extracellularly. The three barley proteins were found to inhibit growth of Trichoderma harzianum in microtiter plate assays using approximately 10 micrograms/ml concentrations and in lower concentrations in a synergistic way when mixed either with barley chitinase C (a PR-3 type protein) or with barley protein R (a PR-5 type protein). Structurally similar proteins were detected in wheat, rye and oats grain extracts.

Amino Acid Sequence↗
PubMed1994

Structural features of plant chitinases and chitin-binding proteins.

Structural features of plant chitinases and chitin-binding proteins are discussed. Many of these proteins consist of multiple domains, of which the chitin-binding hevein domain is a predominant one. X-ray and NMR structures of representatives of the major classes of these proteins are available now, and are used to describe the structures of the other ones. Conserved positions of Cys residues can be taken as evidence for identically located disulfide bridges or cysteine residues. The current classification of chitinases is unsatisfactory and needs to be replaced by an evolutionarily more correct one. As the currently known three-dimensional structures of chitinases are those from barley and the rubber tree, Hevea brasiliensis, it is proposed to adopt the designation b-type (classes I, II and IV) and h-type (classes III and V) chitinases, respectively.

Amino Acid Sequence↗
PubMed1993

Characterization of a monoclonal antibody against latex protein associated with latex allergy.

Several hybridomas were produced against antigens extracted from the latex sap of Hevea brasiliensis. One of the monoclonal antibodies (LA-E3) reacted with antigens demonstrating binding to patient sera on crossed enzyme immunoelectrophoresis. This monoclonal antibody reacted with 2 of 10 glove extracts studied and with both Malaysian and Indian latex plant extracts. The antigens purified with monoclonal antibody affinity chromatography demonstrated specific IgE in the sera of patients with latex allergy as determined by ELISA. This monoclonal antibody can thus be utilized to obtain reliable antigens useful in the diagnosis of latex sensitivity, although additional antigens will likely be necessary to enhance sensitivity and specificity.

Adolescent↗
PubMed1994

Demonstration by mass spectrometry that pseudo-hevein and hevein have ragged C-terminal sequences.

The primary structure of pseudo-hevein, a minor hevein component from the latex of the rubber tree, Hevea brasiliensis, was determined. Six differences with the sequence of the major hevein component were found, one of which is a replacement of tryptophan by tyrosine in the carbohydrate binding region of the molecule. Analysis by ion-spray mass spectrometry showed that pseudo-hevein has a heterogeneous C-terminal extension of several glycine residues and that hevein itself also contains minor components with additional C-terminal amino-acid residues. A seventh difference between the two sequences occurs in these extensions.

Amino Acid Sequence↗
PubMed1990

Contact urticaria and anaphylaxis to natural latex.

Immediate allergic reaction to natural latex of Hevea brasiliensis has been well documented. We report 17 cases, all in women. Twelve had an anaphylactic reaction during surgery and five had contact urticaria. Reactions to prick tests done through a washed surgical glove and with natural latex were positive in 15 of 17 patients and in 16 of 16 patients, respectively; specific IgE was found in 12 of 17 patients. In 206 control subjects, results of a prick test through a surgical glove were negative.

Adult↗
PubMed2006

Initiator-independent and initiator-dependent rubber biosynthesis in Ficus elastica.

The rubber-producing tree, Ficus elastica (the Indian rubber tree), requires the same substrates for rubber production as other rubber-producing plants, such as Hevea brasiliensis (the Brazilian or Para rubber tree), the major source of commercial natural rubber in the world, and Parthenium argentatum (guayule), a widely studied alternative for natural rubber production currently under commercial development. Rubber biosynthesis can be studied, in vitro, using purified, enzymatically active rubber particles, an initiator such as FPP, IPP as the source of monomer, and a metal cofactor such as Mg2+. However, unlike H. brasiliensis and P. argentatum, we show that enzymatically active rubber particles purified from F. elastica are able to synthesize rubber, in vitro, in the absence of added initiator. In this paper, we characterize, for the first time, the kinetic differences between initiator-dependent rubber biosynthesis, and initiator-independent rubber biosynthesis, and the effect of cofactor concentration on both of these processes.

Ficus↗
PubMed2005

Overexpression and characterization of a novel chitinase from Trichoderma atroviride strain P1.

We describe the overexpression and characterization of a new 30 kDa family 18 chitinase (Ech30) from Trichoderma atroviride strain P1. Sequence alignments indicate that the active site architecture of Ech30 resembles that of endochitinases such as hevamine from the rubber tree (Hevea brasiliensis). The ech30 gene was overexpressed in Escherichia coli without its signal peptide and with an N-terminal His-tag. The enzyme was produced as inclusion bodies, from which active chitinase could be recovered using a simple refolding procedure. The enzyme displayed an acidic pH-optimum (pH 4.5-5.0), probably due to the presence of a conserved Asn residue near the catalytic glutamate, which is characteristic for acidic family 18 chitinases. Studies with oligomers of N-acetylglucosamine [(GlcNAc)(n)], 4-methylumbelliferyl (4-MU) labelled GlcNAc oligomers and beta-chitin reveal enzymatic properties typical of an endochitinase: 1) low activity towards short substrates (kinetic parameters for the hydrolysis of 4-MU-(GlcNAc)2 were K(m), 149+/-29 microM and k(cat), 0.0048+/-0.0005 s(-1)), and 2) production of relatively large amounts of trimers and tetramers during degradation of beta-chitin. Detailed studies with GlcNAc oligomers indicated that Ech30 has as many as seven subsites for sugar binding. As expected for a family 18 chitinase, catalysis proceeded with retention of the beta-anomeric configuration.

Acetylglucosamine↗
PubMed2006

A single amino acid substitution on the surface of a natural hevein isoform (Hev b 6.0202), confers different IgE recognition.

Decreased immune reactivity of isoforms of major allergens has been reported. However, such claims have always been based on experiments with recombinant proteins. This work describes the molecular and physicochemical characterization of a hevein (Hev b 6.0201) natural isoform (Hev b 6.0202), which is present in rubber latex from Hevea brasiliensis. The isoallergen has a single substitution Asn14Asp, which gives rise to local differences in the surface potential, as observed from the crystal structure presented here. Besides, ELISA inhibition using serum pools of adult and pediatric patients showed reduced IgE-binding capacity ( approximately 27%) with the isoallergen. Overall, these results are relevant to delineate crucial residues involved in this dominant discontinuous epitope.

Amino Acid Sequence↗
PubMed2004

Expression of the B subunit of the heat-labile enterotoxin of Escherichia coli in tobacco mosaic virus-infected Nicotiana benthamiana plants and its characterization as mucosal immunogen and adjuvant.

We have produced biologically active recombinant (r) LTB, the nontoxic B subunit of heat-labile toxin (LT) of Escherichia coli in tobacco mosaic virus (TMV)-infected Nicotiana benthamiana plants. We amplified the LTB encoding sequence with its leader and introduced a hexahistidyl tag and an endoplasmic reticulum retention signal. The resulting product was ligated into a TMV-based plant viral expression vector that was used for the generation of recombinant viral RNA. Eighty-nine percent of N. benthamiana plants inoculated with the recombinant viral RNA were systemically infected as determined by anti-TMV enzyme-linked immunosorbent assay (ELISA) experiments. The rLTB monomer was identified by LT-specific as well as by histidyl-tag-specific immunoblots. rLTB from plant extracts of TMV-infected N. benthamiana leaves was purified to give 75 microg rLTB pentamers per gram fresh plant material and was capable of binding G(M)1 ganglioside. The immunogenicity of the plant-produced rLTB was tested in mice and showed that intranasal application of rLTB (15 microg per mouse) induced LTB-specific IgG1 antibodies. To prove its adjuvanticity, rLTB was intranasally co-administered with the Hevea latex allergen Hev b 3, leading to allergen-specific IgG1 and IgG2a antibody production. The fact that intranasal application of rLTB and Hev b 3 prior to systemic challenge with the allergen enhanced the Th2 responses at the humoral and cellular level indicated that rLTB promoted immune responses that were naturally induced by the antigen/allergen. In conclusion, these results indicate that the plant viral expression system is suitable for the rapid large-scale production of biologically active LTB with strong mucosal adjuvant capacity.

Adjuvants, Immunologic↗
PubMed2005

Molecular cloning of Indian jujube (Zizyphus mauritiana) allergen Ziz m 1 with sequence similarity to plant class III chitinases.

Indian jujube (Zizyphus mauritiana) is a sweet fruit that is abundantly cultivated in Taiwan. We have previously identified 42 and 30 kDa allergens that are cross-reactive with latex allergen from crude Indian jujube extract. This study aimed to clone the 30 kDa Ziz m 1 Z. mauritiana allergen. The Ziz m 1 encoding cDNA was isolated from a ZAPII cDNA library constructed from Z. mauritiana mRNA, sequenced and expressed in Pichia pastoris. The protein predicted from the cDNA sequence has 330 amino acids, the first 25 of which constituted a putative signal peptide. The deduced molecular mass of the mature protein is 33.86 kDa, while its isoelectric point is estimated at 4.36. The recombinant Ziz m 1 showed chitinase activity, possessed IgE binding capacity, and had IgE cross-reactivity with the latex allergen. Moreover, anti-recombinant Ziz m 1 antibody-based ELISA was able to detect commercial skin testing latex reagent, laboratory prepared latex and Indian jujube extracts. Recombinant Ziz m 1 showed 87.5% skin reactivities on eight latex- and Indian jujube-sensitive subjects. Although no sequence similarity was found to other known allergens, Ziz m 1 was found to have amino acid sequence identity (39-45.3%) to many plant chitinases including chitinase (45.2%) of Hevea brasiliensis (hevamine), class III chitinases of Vigna angularis (45.3%), Capsicum annuum (44.7%) and Oryza sativa (41.2%). A conserved domain search revealed that Ziz m 1 belongs to the family 18 glycosyl hydrolases. The recombinant allergen may therefore be of value for diagnosis and therapeutic purposes, and the further characterization of Indian jujube allergen may help to elucidate the mechanism underlying latex-fruit syndrome.

Allergens↗
PubMed2006

Identification and comparison of natural rubber from two Lactuca species.

Renewed interest in the identification of alternative sources of natural rubber to Hevea brasiliensis has focused on the Compositae family. In our search for Compositae models for rubber synthesis, we extracted latex from stems of two lettuce species: Lactuca serriola, prickly lettuce, and Lactuca sativa cv. Salinas, crisphead lettuce. Both species contained cis-1,4-polyisoprene rubber in the dichloromethane-soluble portions of their latex, and sesquiterpene lactones in their acetone-soluble portions. The rubber from both species and their progeny had molecular weights in excess of 1,000,000g/mol, and polydispersity values of 1.1. Rubber transferase activity was detected across a range of farnesyl diphosphate initiator concentrations, with decreased activity as initiator concentrations exceeded putative saturation. These results add lettuce to the short list of plant species that produce high molecular weight rubber in their latex. Due to the genomic and agronomic resources available in lettuce species, they provide the opportunity for further dissection of natural rubber biosynthesis in plants.

Lactones↗
PubMed2001

Similarities and differences in rubber biochemistry among plant species.

This report reviews aspects of the biochemical regulation of rubber yield and rubber quality in three contrasting rubber-producing species, Hevea brasiliensis, Parthenium argentatum and Ficus elastica. Although many similarities are revealed, considerable differences also exist in enzymatic mechanisms regulating biosynthetic rate and the molecular weight of the rubber biopolymers produced. In all three species, rubber molecule initiation, biosynthetic rate and molecular weight, in vitro, are dependent upon substrate concentration and the ratio of isopentenyl pyrophosphate (IPP, the elongation substrate, or monomer) and farnesyl pyrophosphate (FPP, an initiator), but these parameters are affected by intrinsic properties of the rubber transferases as well. All three rubber transferases are capable of producing a wide range of rubber molecular weight, depending upon substrate concentration, clearly demonstrating that the transferases are not the prime determinants of product size in vivo. However, despite these commonalities, considerable differences exist between the species with respect to cosubstrate effects, binding constants, effective concentration ranges, and the role of negative cooperativity in vitro. The P. argentatum rubber transferase appears to exert more control over the molecular weight it produces than the other two species and may, therefore, provide the best prospect for the source of genes for transformation of annual crop species. The kinetic data, from the three contrasting rubber-producing species, also were used to develop a model of the rubber transferase active site in which, in addition to separate IPP and allylic-PP binding sites, there exists a hydrophobic region that interacts with the linear portion of allylic-PP initiator proximal to the pyrophosphate. Substrate affinity increases until the active site is traversed and the rubber interior of the rubber particle is reached. The kinetic data suggest that the hydrophobic region in H. brasiliensis and F. elastica is about 1.8 nm long but only 1.3 nm in P. argentatum. The estimates are supported by measurements of the rubber particle monolayer membrane using electron paramagnetic resonance spectroscopy.

Plants↗
PubMed1996

The 14.6 kd rubber elongation factor (Hev b 1) and 24 kd (Hev b 3) rubber particle proteins are recognized by IgE from patients with spina bifida and latex allergy.

Two major water-insoluble proteins are located on the surface of rubber particles in Hevea brasiliensis latex. A 14.6 kd protein (Hev b 1), found mainly on large rubber particles (> 350 mm in diameter), and a 24 kd protein (Hev b 3), found mainly on small rubber particles (average diameter, 70 nm), are recognized by IgE from patients with spina bifida and latex allergy. Although Hev b 1 (also called the rubber elongation factor [REF]) has previously been reported as a major latex allergen, this conclusion has been disputed on the basis of results from other studies. The allergenicity of Hev b 1 is verified in this study by testing the recombinant protein generated from its gene. Because allergenicity is confined to patients with spina bifida and not observed in adults sensitive to latex, it is not a major latex allergen. The identification of Hev b 3 as another allergen originating from rubber particles is confirmed by immunogold labeling and electron microscopy. Observations with the monoclonal antibody USM/RC2 developed against Hev b 3 show that the protein has a tendency to fragment into several polypeptides of lower molecular weight (from 24 kd to about 5 kd) when stored at -20 degrees C. There is also indication of protein aggregation from the appearance of proteins with molecular weights greater than 24 kd. Fragmentation of Hev b 3 is induced immediately on he addition of latex B-serum, which is normally compartmentalized in the lutoids in fresh latex. In the preparation of ammoniated latex (used for the manufacture of latex products), the lutoids are ruptured, and the released B-serum reacts with Hev b 3 on the rubber particles to give rise to an array of low molecular weight polypeptides that are allergenic to patients with spina bifida.

Adult↗
PubMed1996

Natural rubber latex skin testing reagents: safety and diagnostic accuracy of nonammoniated latex, ammoniated latex, and latex rubber glove extracts.

BACKGROUND: Nonammoniated latex, ammoniated latex, and rubber glove extracts are the only sources of natural rubber (Hevea brasiliensis) latex that have potential for use as skin testing reagents in the diagnosis of latex allergy. Their diagnostic sensitivity and specificity as skin test reagents are unknown. OBJECTIVE: We conducted a phase 1/2 clinical study to examine the safety and diagnostic accuracy (sensitivity and specificity) of nonammoniated latex, ammoniated latex, and rubber glove extracts as skin test extracts to identify the most efficacious source material for future skin test reagent development. METHODS: Twenty-four adults not allergic to latex, 19 adults with hand dermatitis or pruritus, and 59 adults with a latex allergy were identified by clinical history. All provided blood and then received puncture skin tests and intradermal skin tests with nonammoniated latex, ammoniated latex, and rubber glove extracts from Malaysian H. brasiliensis latex by use of sequential titration. A glove provocation test and IgE anti-latex RAST were used to clarify positive history-negative skin test response and negative history-positive skin test response mismatches. RESULTS: All three extracts were biologically safe and sterile. After normalization to 1 mg/ml of total protein, all three extracts produced equivalent diagnostic sensitivity and specificity in puncture skin tests and intradermal skin tests at various extract concentrations. Optimal diagnostic accuracy was safely achieved at 100 micrograms/ml for intradermal skin tests (e.g., nonammoniated latex: puncture skin test sensitivity 96%, specificity 100%; intradermal skin test sensitivity 93%, specificity 96%). The presence of IgE antibody in skin was highly correlated with IgE anti-latex in serum (nonammoniated latex: r = 0.98, p < 0.001; ammoniated latex: r = 0.94, p < 0.001; rubber glove extract: r = 0.96, p < 0.001). All five available subjects with a positive history, negative skin test response, and absence of IgE antibody in serum had a negative glove provocation test response, indicating no clinical evidence of latex allergy. No systemic or large local allergic reactions were observed with puncture skin tests or intradermal skin tests. CONCLUSIONS: Equivalent diagnostic sensitivity and specificity were observed with the nonammoniated latex, ammoniated latex, and rubber glove extract skin test reagents after normalization for total protein; nonammoniated latex may be considered the reagent of choice on the basis of practical quality control and reproducibility considerations.

Adult↗