Isolation and characterization of a bioactive mannose-binding protein from the Chinese chive Allium tuberosum

A mannose-binding protein was isolated from two different cultivars of the Chinese chive Allium tuberosum by extraction with 0.2 M NaCl, ammonium sulfate precipitation, and affinity chromatography on mannose agarose and fetuin agarose. It exhibited hemagglutinating activity toward rabbit erythrocytes. The lectin (agglutinin) was adsorbed on the mannose-agarose column, but not on the fetuin-agarose column. This A. tuberosum lectin (ATL) is unglycosylated, and not sialic acid binding. Lectins isolated from the two cultivars exhibited the same molecular mass of 25 kDa on gel filtration (Superose 12) and 12.5 kDa on SDS-polyacrylamide gel electrophoresis, indicating that they might be a dimeric protein composed of two identical subunits. The N-terminal amino acid sequence analysis of the lectin of various cultivars of A. tuberosum revealed that they were identical and showed 50%, or more, homology to the lectins from Galanthus nivalis (family Amaryllidaceae), Narcissus tazetta (family Amaryllidaceae), and Aloe arborescenes (family Liliaceae).     

Novel protein from Labramia bojeri A. DC. seeds homologue to Kunitz-type trypsin inhibitor with lectin-like properties

This study starts by isolating and characterizing the first protein from Labramia bojeri seeds, which belong to the Sapotaceae family. The purified lectin analyzed by SDS-PAGE with and without beta-mercaptoethanol shows two protein bands (M(r) = 19 and 20 kDa), which cannot be resolved. Protein bands have shown similar characteristics as molecular masses, determined by gel filtration and native gel; N-terminal sequences presented a difference in their isoelectric points. We have suggested that those protein bands might be variants of the protein named Labramin. The sequence database search has shown that the N-terminal sequence of Labramin presented a high degree of homology to Kunitz-type trypsin inhibitor (82-52%) despite no trypsin inhibition activity detection. The lectin-like form from Labramin was better inhibited by glycoproteins and has also presented growth inhibition of the fungus Colletotrichum lindemuthianum and the yeast Saccharomyces cerevisiae, but it has not presented an apparent effect on Fusarium oxysporum.     

Characterization of globulins from common vetch (Vicia sativa L.)

The proteins from Vicia sativa L. (common vetch) seeds were investigated. Protein comprises approximately 11.4% of the seed fresh weight, >50.8% of which is composed by globulins and 43.6% by albumins. The globulins may be fractionated into two main components, which were named alpha-vicinin (comprising 73% of the total globulin fraction, and hence >37% of the total seed protein) and beta-vicinin. Two minor globulin components are also present, gamma-vicinin and delta-vicinin. alpha-Vicinin, the legumin-like globulin, with a sedimentation coefficient of 10.6 S, is a nonglycosylated, disulfide-bond-containing globulin, composed of a group of subunits with molecular masses ranging from 50 to 78 kDa. Upon reduction, each of these subunits releases a heavy polypeptide chain (34-66 kDa) and a light polypeptide chain (21-23 kDa). beta-Vicinin, the vicilin-like globulin, with a sedimentation coefficient of 7.7 S, is a nonglycosylated globulin that contains no disulfide bonds and consists of two major polypeptides with molecular masses of 58 and 66 kDa. gamma-Vicinin is a minor, glycosylated, disulfide-bond-containing globulin. In the reduced form, it comprises six polypeptide chains with molecular masses of 12, 19, 21, 22, 23, and 31 kDa. Finally, delta-vicinin is a minor, highly glycosylated globulin that exhibits hemagglutinating activity. It is composed of a major 47 kDa polypeptide and two minor (33 and 38 kDa) polypeptides. N-terminal sequencing of the delta-vicinin 47 kDa polypeptide revealed no homology to any other known storage protein.     

Storage proteins from Lathyrus sativus seeds

The proteins from Lathyrus sativus Linn. (chickling vetch or grass pea) seeds were investigated. Protein constitutes approximately 20% of the seed dry weight, >60% of which is composed by globulins and 30% by albumins. A single, 24 kDa polypeptide comprises more than half of the protein present in the albumin fraction. The globulins may be fractionated into three main components, which were named alpha-lathyrin (the major globulin), beta-lathyrin, and gamma-lathyrin. alpha-Lathyrin, with a sedimentation coefficient of approximately 18S, is composed of three main types of unglycosylated subunits (50-66 kDa), each of which produce, upon reduction, a heavy and a light polypeptide chain, by analogy with 11S. beta-Lathyrin, with a sedimentation coefficient of 13S, is composed by a relatively large number of subunits (8-66 kDa). Two major polypeptides are glycosylated and exhibit structural similarity with beta-conglutin from Lupinus albus. One of these possesses an internal disulfide bond. gamma-Lathyrin, with a sedimentation coefficient of approximately 5S, contains two interacting, unglycosylated polypeptides, with no disulfide bonds: the major 24 kDa albumin and the heavier (20 kDa) polypeptide chain of La. sativus lectin.     

Purification of a lectin from the marine red alga Gracilaria cornea and its effects on the cattle tick Boophilus microplus (Acari: Ixodidae)

A lectin was purified from the seaweed Gracilaria cornea by hydrophobic interaction chromatography on phenyl-Sepharose CL-4B followed by affinity chromatography on immobilized mucin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of G. cornea lectin (GCL) revealed a single protein band of approximately 60 kDa, whereas by gel filtration on Sephadex G-100 its native molecular mass was 66 kDa. GCL exhibited a single isoeletric point of 4.3 and a 52.5% content of neutral sugars. Furthermore, the EDTA-treated lectin did not show any significant decrease in its ability to agglutinate trypsin-treated chicken erythrocytes. These data suggest that GCL is an acidic, monomeric glycoprotein that probably does not require divalent metal ions for its hemagglutinating activity. GCL hemagglutinating activity was not inhibited by any of the mono-, di-, and trisaccharides tested but was by the complex glycoproteins fetuin and porcine stomach mucin. Exposure of engorged females of the cattle tick (Boophilus microplus) to 0.1 mg mL(-1) GCL significantly (P < 0.05) reduced the female weight after the oviposition period, the egg mass weight, the hatching period, and the mean larvae survival time.     

New mannose-binding lectin isolated from the rhizome of Sarsaparilla Smilax glabra Roxb. (Liliaceae)

A new mannose-binding lectin, designated SGM2, was isolated from the rhizome of a Chinese medicinal herb Smilax glabra (also known as sarsaparilla in general) by saline extraction, ammonium sulfate precipitation and fractionation, and affinity chromatography on fetuin- and mannose-agarose. SGM2 is shown to have a molecular mass of 37 kDa on gel filtration and 12.5 kDa on SDS-PAGE, indicating that it is a trimeric protein composed of three identical subunits. When the first 30 amino acid residues at the N-terminal were compared, SGM2 had approximately 40% homology with those of some other monocots. SGM2 had the property of hemagglutinating activity toward rabbit erythrocytes, which could be reversed by mannose and mannose polymers. SGM2 exhibited antiviral activities against both herpes simplex virus type 1 (HSV-1) and respiratory syncytial virus (RSV) with the same EC(50) of 8.1 microM.     

Purification and characterization of a methylene urea-hydrolyzing enzyme from Rhizobium radiobacter (Agrobacterium tumefaciens)

Slow-release fertilizers are gaining acceptance to increase fertilizer use efficiency and reduce environmental impact. The release of nitrogen from methylene urea, a common slow release N fertilizer, is controlled by microbial decomposition. An enzyme hydrolyzing slow-release nitrogen fertilizer, methylene urea, was purified from Rhizobium radiobacter (Agrobacterium tumefaciens) to homogeneity using a four-step purification procedure with an overall yield of 3%. The active enzyme has a molecular mass of approximately 180 kDa determined by size exclusion chromatography, and the SDS page of the purified protein indicated three subunits of different sizes (62, 34 and 32 kDa). The N-terminal amino acid sequence of the 62 kDa fragment indicates identity with urease subunits from Mycobacterium tuberculosis (73%) and Helicobacter pylori (71%). However, for the internal amino acid sequences of the 62 kDa fragment no matches with known proteins were found. Some internal peptides in the smaller subunits (32 and 34 kDa) are homologous to urease subunits and unknown proteins in Agrobacterium tumefaciens. Based on the kinetic properties, substrate selectivity, and inhibition characteristics, the novel enzyme (MUase) is an intracellular enzyme complex with urease activity. The enzymatic mechanism of methylene urea breakdown was studied using a novel LC-MS method for MU analysis, which indicates that all cold-water soluble nitrogen forms of methylene urea are subjected to hydrolysis, and the hydrolysis proceeds via methylurea, urea and other yet unidentified hydrolysis-products, suggesting that the isolated enzyme complex performs a multistep hydrolysis. The microbiological and molecular data is useful in determining the soil factors affecting the efficacy of methylene urea as a slow release fertilizer in agricultural production systems.     

The identification of starch phosphorylase in the developing mungbean (Vigna radiata L.)

Starch phosphorylase (SP) in immature mungbean (Vigna radiata L. cv KPS1) seed soluble extract was detected by in situ activity staining and identified by MALDI-TOF mass analysis. After in situ SP assay on native-PAGE, a major starch-enzyme complex was located on the gel zymogram in a dose-dependent manner. This complex depicted two major SP-activity related proteins, 105 kDa and 55 kDa, by SDS-PAGE. The mass and predicted sequence of the tryptic fragments of the isolated 105 kDa protein, analyzed by MALDI-TOF spectroscopy and bioinformatic analysis, confirmed it to be mungbean SP as a result of high similarity to the L-SP of known plant. Polyclonal antibodies raised from the 55 kDa recognized both the 105 kDa and the 55 kDa proteins on the Western blot and neutralized partial SP activity, indicating that the two proteins were immunologically related. The 55 kDa protein possess high similarity to the N-terminal half of the 105 kDa SP was further confirmed. The SP activity and the activity stained protein density in mungbean soluble extract decreased as the seed size increased during early seed growth. These data indicate that mungbean 105 kDa SP and SP activity-related 55 kDa were identified in the developing mungbean.     

Lectin from Phaseolus acutifolius var. escumite: chemical characterization, sugar specificity, and effect on human T-lymphocytes

Purification of the lectin from Phaseolus acutifolius var. escumite was achieved by affinity chromatography on a column containing glutaraldehyzed membranes from blood group O erythrocytes. The lectin is a tetrameric glycoprotein of 121 kDa with 10% of sugar by weight composed by four subunits of 30 kDa as determined by SDS-PAGE. The lectin is composed of four isolectins as determined by ion-exchange chromatography on a mono-S column. The lectin and its isolectins showed identical NH2 terminal residues (ANDLSFNFQR FNETN) with homology to the PHA leucoagglutinin-precursor. Peptide mass fingerprint from each lectin isoform determined from tryptic peptides by MALDI-TOF (matrix assisted laser desorption ionization-time-of-flight) showed differences among subunits, thus suggesting microheterogeneity in their amino acid sequences or different glycosylation patterns. The lectin and its four isolectins agglutinated erythrocytes without serological specificity and showed mitogenic activity on human leukocytes; moreover, the main effect was rather toward CD8+ than to CD4+ human peripheral lymphocytes. The lectin from escumite was not inhibitable by simple sugars; however, the specificity of the lectin and its isoforms was mainly addressed toward galactose residues present in bi- or triantennary N-acetyllactosamine-type glycans.     

Purification and characterization of a latent polyphenol oxidase from beet root (Beta vulgaris L.)

Polyphenol oxidase (PPO) has been extracted from beet root, in both soluble and membrane fractions. In both cases, the enzyme was in its latent state, and it was activated by sodium dodecyl sulfate. PPO was purified to apparent homogeneity. The soluble PPO purification was achieved by hydrophobic interaction chromatography and gel filtration chromatography, with apparent molecular mass of 55 kDa. The membrane PPO purification was achieved by anion exchange chromatography and gel filtration with apparent molecular mass of 54 kDa. A totally denaturing SDS-PAGE indicated the presence of a single polypeptide with an apparent molecular mass of 60 kDa for both fractions, with the band also revealed by Western blot. A partially denaturing SDS-PAGE stained a single active 36 kDa band for both fractions. Under native isoelectric focusing, a major acidic band of pH 5.2 was detected in both fractions. Kinetic characterization of PPO on the natural substrate l-dopa was carried out.     

High molecular weight glutenin subunits in some durum wheat cultivars investigated by means of mass spectrometric techniques

The primary structures of high molecular weight glutenin subunits (HMW-GS) of 5 Triticum durum Desf. cultivars (Simeto, Svevo, Duilio, Bronte, and Sant'Agata), largely cultivated in the south of Italy, and of 13 populations of the old spring Sicilian durum wheat landrace Timilia (Triticum durum Desf.) (accession nos. 1, 2, 3, 4, 7, 8, 9, 13, 14, 15, SG1, SG2, and SG3) were investigated using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and reversed-phase high performance liquid chromatography/nanoelectrospray ionization mass spectrometry (RP-HPLC/nESI-MS/MS). M(r) of the intact proteins determined by MALDI mass spectrometry showed that all the 13 populations of Timilia contained the same two HMW-GS with 75.2 kDa and 86.4 kDa, whereas the other durum wheat cultivars showed the presence of the expected HMW-GS 1By8 and 1Bx7 at 75.1 kDa and 83.1 kDa, respectively. By MALDI mass spectrometry of the tryptic digestion peptides of the isolated HMW-GS of Timilia, the 1Bx and 1By subunits were identified as the NCBInr Acc. No AAQ93629, and AAQ93633, respectively. Sequence verification for HMW-GS 1Bx and 1By both in Simeto and Timilia was obtained by MALDI mass mapping and HPLC/nESI-MSMS of the tryptic peptides. The Bx subunit of Timila presents a sequence similarity of 96% with respect to Simeto, with differences in the insertion of 3 peptides of 5, 9, and 15 amino acids, for a total insertion of 29 amino acids and 25 amino acid substitutions. These differences in the amino acidic sequence account for the determined Δm of 3294 Da between the M(r) of the 1Bx subunits in Timilia and Simeto. Sequence alignment between the two By subunits shows 10 amino acid substitutions and is consistent with the Δm of 148 Da found in the MALDI mass spectra of the intact subunits.     

N-acetyl-D-galactosamine-specific lectin isolated from the seeds of Carica papaya

N-Acetyl-D-galactosamine (GalNAc)-specific lectins are of great interest because they have been reported to detect tumor-associated antigens of malignant cells. We isolated a novel lectin from Carica papaya seeds, named C. papaya lectin (CPL). Purification of the lectin involved ammonium sulfate fractionation and DEAE anion exchange and repeated gel filtration chromatography. Inhibition of CPL causing hemagglutination on human erythrocytes showed that the lectin shows specificity to GalNAc and lactose. Surface plasmon resonance further revealed that the lectin possesses high specificity toward GalNAc with a dissociation constant of 5.5 × 10(-9) M. The lectin is composed of 38- and 40-kDa subunits with a molecular mass of ～804 kDa estimated by size-exclusion high-performance liquid chromatography. Incubation of CPL with Jurkat T cells showed significant induction of IL-2 cytokine, which suggests that CPL has potent immunomodulatory effects on immune cells.     

Amaranth (Amaranthus hypochondriacus) vicilin subunit structure

The 7S-globulin fraction is a minor component of the amaranth storage proteins. The present work provides new information about this protein. The amaranth 7S-globulin or vicilin presented a sedimentation coefficient of 8.6 ± 0.6 S and was composed of main subunits of 66, 52, 38, and 16 kDa. On the basis of mass spectrometry (MS) analysis of tryptic fragments, the 52, 38, and 16 kDa subunits presented sequence homology with sesame vicilin, whereas the 66 kDa subunit showed sequence similarity with a putative vicilin. Several characteristics of the 66 kDa subunit were similar to members of the convicilin family. Results support the hypothesis that the 7S-globulin molecules are composed of subunits coming from at least two gene families with primary products of 66 and 52 kDa, respectively. According to the present information, amaranth vicilin may be classified into the vicilin group that includes pea, broad bean, and sesame vicilins, among others.     

Purification and characterization of an N-acetylglucosamine-binding lectin from Koelreuteria paniculata seeds and its effect on the larval development of Callosobruchus maculatus (Coleoptera: Bruchidae) and Anagasta kuehniella (Lepidoptera: Pyralidae)

This study describes the purification of an N-acetylglucosamine-binding lectin from Koelreuteria paniculata seeds and its effects on the larval development of Callobruchus maculatus and Anagasta kuehniella. The lectin (KpLec) was characterized and isolated by gel filtration, affinity column, and reverse phase chromatography. SDS-PAGE indicated that this lectin is a dimer composed of subunits of 22 and 44 kDa. The N terminus exhibited 40% similarity with Urtiga dioica agglutinin. KpLec was tested for anti-insect activity against C. maculatus and A. kuehniella. With regard to C. maculatus, an artificial diet containing 0.7 and 1% KpLec produced LD(50) and ED(50) value, respectively. However, for A. kuenhiella, an artificial diet containing 0.65% KpLec produced an LD(50), whereas 0.2% KpLec produced an ED(50). The transformation of genes coding for this lectin could be useful in the development of insect resistance in important agricultural crops.     

The wide diversity of structurally similar wine proteins

In the present work, single grape variety wines, Moscatel and Arinto, were used. Analysis by denaturing polyacrylamide gel electrophoresis of the wine proteins revealed the presence of only a few polypeptides ranging in molecular mass from 15 to 30 kDa. However, a more detailed examination of the whole protein fraction, by a combination of techniques, showed that these wines contain a very large number (many tens and, possibly, many more) of distinct polypeptides, exhibiting similar molecular masses but different electrical charges. The results obtained using highly specific antibodies and N-terminal sequencing indicate that there is structural similarity among most of the wine polypeptides. These observations can be explained by the existence of a common precursor to most or all of the wine proteins, which could generate all of the detected polypeptides by limited proteolysis. Comparison of the N-terminal sequences of the polypeptides isolated from Moscatel wine with proteins from other sources revealed a high degree of homology to pathogenesis-related proteins.     

Evidence for a tetrameric form of iceberg lettuce (Lactuca sativa L.) polyphenol oxidase: purification and characterization

Polyphenol oxidase from iceberg lettuce (Lactuca sativa L.) chloroplasts was released from the thylakoid-membrane by sonication, and it was extensively purified to homogeneity as judged by SDS-PAGE. Purification was achieved by ammonium sulfate fractionation, gel-filtration chromatography, and ion-exchange chromatography. Two molecular forms were separated by gel-filtration chromatography with apparent molecular masses of 188 and 49 kDa. Both forms were characterized by sedimentation analysis with S(20,W) values of 10.2 and 4.1 S, respectively. For the high-molecular-weight form purified to homogeneity, denaturing SDS-PAGE indicated a molecular mass of 60 kDa. Thus, from these data we suggest that lettuce polyphenol oxidase is a tetramer of identical subunits.     

Purification and partial characterization of an acid phosphatase from Spirodela oligorrhiza and its affinity for selected organophosphate pesticides

An acid phosphatase from the aquatic plant Spirodela oligorrhiza (duckweed) was isolated by fast protein liquid chromatography and partially characterized. The enzyme was purified 1871-fold with a total yield of 40%. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the pure acid phosphatase resolved a single protein band that migrated to approximately 60 kDa. Nondenaturing SDS-PAGE electrophoresis revealed a single protein band around 120 kDa after staining with Coomassie Brilliant blue. Quantitative gel filtration chromatography estimated a native molecular mass of this enzyme to be 120 kDa. Thus, this acid phosphatase likely functions as a homodimer, consisting of two similar 60 kDa subunits. An electrophoretic technique using the flourogenic substrate 4-methylumbelliferyl phosphate enabled visualization of an acid phosphatase activity that corresponded to the protein band at 120 kDa on a nondenaturing PAGE gel. It was determined that the acid phosphatase had a pH optimum of 6.0 at 25 degrees C. The enzyme activity appeared to be stable over a broad range of temperatures (10-40 degrees C) and in the presence of the metals Zn2+, Mn2+, and Mg2+ as well as the chelating agents ethylenedinitrilotetraacetic acid and ethylene glycol tetraacetic acid. It was shown that this acid phosphatase could hydrolyze a variety of physiological organophosphate compounds including beta-glycerophosphate, phosphoserine, adenosine triphosphate, adenosine diphosphate, adenosine monphosphate, and pyrophosphate. Furthermore, analysis using capillary electrophoresis demonstrated that this hydrolytic enzyme could transform a wide array of organophosphate pesticides including S-2-ethylthioethyl O,O-dimethylphosphorothioate (demeton-S-methyl); S-1,2-bis(ethoxycarbonyl)ethyl O,O-dimethylphosphorodithioate (malathion); O,O-dimethyl O-4-nitrophenyl (paraoxon); O,O,O,O-tetraethyldithiopyrophosphate (sulfatep); O-2-chloro-4-nitrophenyl O,O-dimethylphosphorothioate (dicapthon); and 2,2-dichlorovinyl dimethylphosphate (dichlorvos).     

Purification and characterization of an alpha-mannosidase from the tropical fruit babaco ( Vasconcellea x heilbornii Cv. babaco)

An alpha-mannosidase (EC 3.2.1.24) present in the lyophilized latex of babaco ( Vasconcellea heilbornii ) has been purified to apparent homogeneity by native PAGE. The purification involves a three-step procedure with successive anion exchange with Q Sepharose HP, lectin affinity chromatography using ConA Sepharose 4B, and gel filtration using Superdex 200 prep grade. The molecular mass was determined to be in the range of 260-280 kDa by Superdex 200 prep grade gel filtration, and isoelectric focusing showed a pI range between 5.85 and 6.55, suggesting different glycosylated isoforms. The optimal temperature for the alpha-mannosidase was determined to lie between 50 and 60 degrees C, and the optimal pH was 4.5 at 50 degrees C. The K(m) value for p-nitrophenyl alpha-mannopyranoside (pNPM) was found to be 1.25 mM and the V(max), 2.4 microkat mg(-1) at 50 degrees C and 1.94 microkat mg(-1) at 40 degrees C. The pure alpha-mannosidase was specific for mannose and did not display activity for any other tested synthetic substrates.     

Characterization of Thiamin‐Binding Protein from Wheat Germ

A thiamin‐binding protein was isolated from wheat germ (Triticum aestivum). Its molecular mass was estimated as 120,000 Da consisting of two 56,000‐subunits. The protein contained a large amount of glutamine or glutamic acid (15.4 mol%), arginine (12.5 mol%), and glycine (12.0 mol%). The levels of tyrosine, methionine, tryptophan, and cysteine in the protein were low. Optimum pH for its thiamin‐binding activity was pH 8.0. It bound free thiamin specifically, not thiamin phosphates. The apparent dissociation and maximum bound values for the thiamin‐binding were 2.52 μM and 9.34 nmol/mg of protein, respectively. Properties of the thiamin‐binding protein from wheat germ were similar to those of the thiamin‐binding protein from rice seeds, but not from buckwheat, sesame, or sunflower seeds.     

Immunological characterization of recombinant soy protein allergen produced by Escherichia coli expression system

To elucidate the molecular mechanism of the allergenicity of soybean P34 protein recognized as the most allergenic protein in soybean, the protein was expressed in Escherichia coli transformed with a plasmid carrying P34 cDNA. SDS-PAGE pattern showed that the molecular weight of the recombinant P34 was approximately 2 kDa less than that of the native soybean P34. The difference in the molecular mass between these two proteins could be due to the native P34 in soybean being glycosylated at position Asn(170), whereas the recombinant protein generated in E. coli lacks this post-translational modification. Immunoblot analysis showed that both soybean and recombinant P34 proteins cross-reacted not only with polyclonal and monoclonal antibodies produced against P34 and crude soybean protein but also with patients' sera. The results suggest that the recombinant P34 is immunologically reactive, indicating that both proteins have similar epitope structures. Thus, the recombinant P34 produced by the E. coli expression system can be used as a standard allergen for molecular design to reduce the allergenic structure.