Deglycosylation of glycoproteins by trifluoromethanesulfonic acid

Apolipoprotein J is associated with paraoxonase in human plasma

Apolipoprotein J (apoJ)-containing high-density lipoproteins (HDL), isolated from human plasma by immunoaffinity chromatography, are associated with apoAI and a protein of approximately 44 kDa. In order to advance our understanding of apoJ's role in the vasculature, a comprehensive investigation was performed to identify and characterize this 44-kDa protein and to study its interaction with apoJ. The 44-kDa protein, a monomeric glycoyslated polypeptide, was identified by N-terminal sequencing as serum paraoxonase. Paraoxonase exists in two oxidation states: one contains all free cysteines while the other has one disulfide bond between Cys42 and Cys284. Northern analysis of eight human tissues shows paraoxonase message present only in the liver. The majority of apoJ/paraoxonase-HDL are 90-140 kDa; however, not all of the plasma paraoxonase is associated with apoJ. The specificity of the apoJ/paraoxonase interaction, inferred by the constant mole ratio of the two proteins in affinity-purified apoJ-HDL, is confirmed in direct binding assays. For purified proteins, there is more than a 5-fold increase in the apparent affinity of apoJ for immobilized paraoxonase as the paraoxonase coating concentration is increased from 0.5 to 2.0 micrograms/mL. Both oxidation states of paraoxonase bind to apoJ with equal affinity. Our data combined with other evidence suggest that the plasma link of apoJ with paraoxonase will be implicated as a predictor of vascular damage.

Glycosylation site of the major allergen from olive tree pollen. Allergenic implications of the carbohydrate moiety

The electrophoretic analysis of purified Ole e I, the major allergen from Olea europaea pollen, reveals the presence of two main variants, glycosylated (20.0 kDa) and non-glycosylated (18.5 kDa) components. The glycosylated variant has been identified as a concanavalin A-binding glycoprotein. Its carbohydrate moiety has a molecular mass of about 1.3 kDa (5% weight of the glycosylated allergen), based on mass spectrometry analysis. Enzymatic treatment of native Ole e I with the specific glycosidase PNGase F accounts for an oligosaccharide N-linked to the polypeptide chain. This treatment does not sensibly modify the secondary structure of the protein but diminishes the affinity of the allergen for specific IgE antibodies. Tryptic digestion of Ole e I reveals the presence of a single carbohydrate-containing peptide. This peptide was recognized by the sera of hypersensitive individuals. The amino acid sequence of this peptide is Phe-Lys-Leu-Asn-Thr-Val-Asn-Gly-Thr-Thr-Arg, asparagine at the seventh being the carbohydrate attaching site. The obtained data are discussed in terms of the potential role of the sugar moiety in the allergenic activity of Ole e I.

Primary structure and characterization of an androgen-stimulated autoantigen purified from mouse seminal-vesicle secretion

A protein extract of mouse seminal-vesicle secretion was used to immunize mature mice (Balb/c) of both sexes. Results of Western-blot analyses for these secretory proteins indicated that only one minor protein component could be recognized by the autoantisera prepared from either autoimmunization of male mice or isoimmunization of female mice. The autoantigen was purified from seminal-vesicle secretion. The purified autoantigen retained the ability to induce autoantibody formation. The autoantigen has glycoprotein characteristics: the majority of the carbohydrate is N-linked and the remainder is O-linked. Rabbit antibodies to the autoantigen were used to isolate the corresponding cDNA from a mouse seminal-vesicle cDNA library. The primary structure deduced from the cDNA sequence was confirmed by direct amino acid sequence determination. The results indicate that the core protein consists of 131 amino acid residues. Analysis of the primary structure indicates that the autoantigen has two potential acceptor sites for the N-linked carbohydrate at Asn-12 and Asn-122, three potential phosphorylation sites for casein kinase II at Thr-55, Ser-68 and Thr-76, and three potential phosphorylation sites for protein kinase C at Thr-28, Thr-40 and Thr-124. The core protein and the carbohydrate portion together have a molecular mass of 19 kDa. Results from Western- and Northern-blot analyses for various tissues indicate that the seminal vesicle is the sole organ producing this autoantigen. Expression of this autoantigen gene was stimulated by testosterone.

Purification and properties of N-acetylglucosaminidase from eggs of the ascidian, Halocynthia roretzi

In several ascidians, beta-D-N-acetylglucosaminidase (GlcNAcase) released from eggs following fertilization is proposed to play a key role in polyspermy block through its binding to the sperm receptor on the vitelline coat [C. C. Lambert (1989) Development 105, 415-420]. In the ascidian Halocynthia roretzi, GlcNAc-specific lectins inhibited the fertilization most strongly among various lectins. Furthermore, GlcNAcase activity was released from the eggs in response to the egg activation. The GlcNAcase was purified from the eggs to apparent homogeneity by chromatographies on DEAE-Toyopearl, SP-Toyopearl, Toyopearl HW-65, and Mono S. The purified enzyme gave a single band on isoelectric focusing with an isoelectric point of 7.0. It gave two bands on SDS/PAGE: the molecular masses of the bands were estimated to be 65 kDa/66 kDa, and 84 kDa/85 kDa under reducing/non-reducing conditions, respectively. The two bands were found to converge to a single band of 56 kDa after deglycosylation, which suggests microheterogeneity in the sugar moiety. The enzyme showed an oligomeric structure with an apparent molecular mass of 520 kDa, estimated by gel filtration. The optimum pH of the activity was around 4.5. The enzyme hydrolyzed both 4-methylumbelliferyl-GlcNAc and 4-methylumbelliferyl-GalNAc, suggesting that it should be characterized as a beta-D-N-acetylhexosaminidase, with Km values of 1.2 mM and 0.52 mM, respectively. The purified enzyme was found to be capable of binding to the vitelline coat in a GlcNAc-specific manner. Immunoblot analysis using antibody raised against the purified GlcNAcase revealed that the enzyme itself is released from the eggs upon fertilization. Thus, the GlcNAcase purified in this study is released from eggs following fertilization and bound to the vitelline coat in order to function in the polyspermy blocking mechanism.

The developmental profile of lactoferrin in mouse epididymis

A sandwich e.l.i.s.a. method was developed to examine the distribution of lactoferrin in mouse reproductive tract. The lactoferrin concentration was found to be much higher in oviduct, uterus, vagina, vas deferens or epididymis than in serum, but the concentration in ovary, testis, seminal vesicle, prostate or coagulating gland was comparable with that in serum. The existence of lactoferrin in male sexual organs was confirmed by Western-blot analyses for tissue proteins. Lactoferrin in male sexual organs was shown to have a molecular mass similar to that of the deglycosylated form of lactoferrin purified from mouse uterine luminal fluid. Northern-blot analyses for total RNA prepared from male sexual organs indicated that only epididymis contained the lactoferrin mRNA. The lactoferrin mRNA was found in the prepubertal period and increased with the growth of epididymis. The mRNA level in prepubertal epididymis could be stimulated by 17 beta-oestradiol, but was not influenced by testosterone.

Morphological and biochemical analyses of amyloid plaque core proteins purified from Alzheimer disease brain tissue

Amyloid plaque cores were purified from Alzheimer disease brain tissue. Plaque core proteins were solubilized in formic acid which upon dialysis against guanidinium hydrochloride (GuHCl) partitioned into soluble (approximately 15%) and insoluble (approximately 85%) components. The GuHCl-soluble fraction contained beta-amyloid1-40, whereas the GuHCl-insoluble fraction was fractionated into six components by size exclusion HPLC: S1 (> 200 kDa), S2 (200 kDa), S3 (45 kDa), S4 (15 kDa), S5 (10 kDa), and S6 (5 kDa). Removal of the GuHCl reconstituted 10-nm filaments composed of two intertwined 5-nm strands. Fractions S5 and S6 also yielded filamentous structures when treated similarly, whereas fractions S1-S4 yielded amorphous aggregates. Chemical analysis identified S4-S6 as multimeric and monomeric beta-amyloid. Immunochemical analyses revealed alpha 1-antichymotrypsin and non-beta-amyloid segments of the beta-amyloid precursor protein within fractions S1 and S2. Several saccharide components were identified within plaque core protein preparations by fluorescence and electron microscopy, as seen with fluorescein isothiocyanate- and colloidal gold-conjugated lectins. We have shown previously that this plaque core protein complex is more toxic to neuronal cultures than beta-amyloid. The non-beta-amyloid components likely mediate this additional toxicity, imposing a significant influence on the pathophysiology of Alzheimer disease.

Biochemical characterization of hamster oviductin as a sulphated zona pellucida-binding glycoprotein

Oviductins are a family of glycoproteins, synthesized and released by oviductal secretory cells, which bind to the zona pellucida of the oocyte after ovulation. Hamster oviductin migrates as diffuse species of 160-350 kDa during SDS/PAGE under reducing as well as non-reducing conditions. In this report, we describe the one-step purification of hamster oviductin using either immuno- or lectin-affinity chromatography. Probing with specific lectins showed that the glycoprotein contains terminal alpha-D-GalNAc, and either terminal alpha-D-NeuAc or non-terminal beta-D-(GlcNAc)2 residues, but fails to react with concanavalin A and Ulex Europeus A-1 lectins which are specific for branched alpha-D-mannose and alpha-L-fucose moieties respectively. Intraovarian oocytes do not contain this glycoprotein and we demonstrate here that the immunoaffinity-purified oviductin readily binds to their zonae pellucidae in vitro, thus mimicking the in vivo phenomenon. Two major immunologically related forms of hamster oviductin (named alpha and beta) were characterized using one- and two-dimensional gel electrophoresis. The alpha-form (160-210 kDa) has an acidic pI of 3.5-4.5 and the beta-form (approx. 210-350 kDa) is localized at the cathodic site in the isoelectric focusing dimension; in between these two major forms lies a smear of minor-charge isomers. Peptide mapping of both major forms with papain and Staphylococcus aureus V8 protease yielded fragments of identical size. Moreover, the two forms share the same N-terminal sequence which display no significant homology with other reported proteins. Treatment with trifluoromethanesulphonic acid showed that a protein with the size and pI of the alpha-form can be generated from the beta-form. Both the alpha- and beta-forms are sulphated on O-linked oligosaccharide side chains but are not phosphorylated. Collectively, these results suggest that the hamster oviductin polymorphism observed in two-dimensional PAGE is a consequence of different glycosylation patterns and not the polypeptide chain itself. Hamster oviductin is mostly O-glycosylated and contains a few N-linked oligosaccharide side chains (approx. 10 kDa). We propose that hamster oviductin is a mucin-type glycoprotein which might act as a protective secretion influencing the first steps of the reproductive process necessary for the normal triggering of fertilization and early embryonic development.

Identification and characterization of an acidic major surface glycoprotein from procyclic stage Trypanosoma congolense

Monoclonal antibodies (mAbs) were derived against the procyclic culture form of Trypanosoma congolense and 14 were selected which bound to the surface of living procyclics in immunofluorescence assays. These antibodies bound to procyclics and epimastigotes of T. congolense (both savannah-type and Kilifi-type) and procyclics of Trypanosoma simiae, but not to procyclics of other species of trypanosomes, to bloodstream forms of several species of trypanosomes or to Leishmania, and were thus life cycle stage- and subgenus-specific. Fluorescence-activated cell sorter analysis with these antibodies showed that the kinetics of expression of the surface antigen during transformation from bloodstream to procyclic forms was similar to that of procyclin or procyclic acidic repetitive protein (PARP) of T. brucei spp. appearing at the cell surface as early as 8 h after initiating transformation. All fourteen antibodies detected broad bands of 40-44 and 28-32 kDa in immunoblot analysis of whole procyclic lysates and were specific for carbohydrate epitopes. The antigen was purified by cation-exchange chromatography and gel electrophoresis, and was shown to be an acidic glycoprotein. Amino acid microanalysis of the purified antigen showed an abundance of glutamic acid/glutamine and alanine. Sequences of peptides produced by cyanogen bromide cleavage matched amino acid sequences predicted by the nucleotide sequence of a gene described in the accompanying paper by Bayne et al. [26]. No sequence similarity to T. brucei procyclin/PARP or to any other protein was found. However, its stage and subgenus specificity, surface disposition, immunodominance, acidity and kinetics of expression during transformation from bloodstream to procyclic forms indicate that the molecule is an analog of procyclin/PARP described in T. brucei spp.

Modulation of sialic acid-binding proteins of rat uterus in response to changing hormonal milieu

A group of sialic acid binding (SAS) agglutinins has been isolated from the rat uteri at different stages [Proestrus (P), estrus (E) and diestrus (D)] of estrous cycle. Studies of biochemical properties indicate that SAS agglutinins are glycoprotein in nature having molecular weights between 28-31 Kd and microheterogenous pI. Function-based characterization revealed that inspite of the fact that all three proteins exhibit sialic acid binding property, the sialic acid binding affinities, calculated from Scatchard analysis, using 4-methylumbelliferyl sialic acid as a ligand, varied in stage specific manner (Ka:D-SAS-9.03 x 10(5) M-1, P-SAS-2.33 x 10(5) M-1, E-SAS-2.13 x 10(5) M-1). Circular dichroism spectra of these three agglutinins suggested that differences exist in the secondary structures of the proteins isolated from different stages. Removal of carbohydrate moiety by trifluoromethane sulfonic acid treatment and CNBr cleavage studies showed some homology between these proteins, however, the variation in the carbohydrate moiety was apparent from the sugar analysis data. Functionally and immunologically these proteins can be grouped as estrogenic and progestogenic SAS agglutinins.

Suggestive evidence for two different mucin genes in rat intestine

In the present report we describe the isolation and sequence of a partial cDNA (M2-798) for a rat intestinal mucin designated M2. A rat intestinal lambda ZAP II cDNA library was screened using a polyclonal antiserum which was prepared against deglycosylated high-molecular-mass glycopeptides of the purified mucin. Mucin cDNA clones were found to contain tandem repeats of 18 nt which encoded a threonine- and proline-rich peptide having a consensus sequence of TTTPDV. This is the same sequence reported recently by Gum, Hicks, Lagace, Byrd, Toribara, Siddiki, Fearney, Lamport and Kim [(1991) J. Biol. Chem. 266, 22733-22738] for a rat intestinal cDNA called RMUC 176. A novel feature present in the cDNA M2-798 is a 246 nt unique region at the 3' end which encodes a hydrophobic sequence of 82 amino acids. RNA blots probed with M2-798 cDNA produced a single hybridization band between 7.5 and 9.0 kb in rat small intestine and colon. An identical hybridization pattern was obtained with a PCR-generated cDNA probe corresponding solely to the unique hydrophobic region of M2-798, demonstrating that this region is encoded by the authentic M2 mRNA. Our data suggest that the unique region of M2 has the potential to be either a transmembrane region, or a domain which mediates hydrophobic interactions of the mucin with other molecules. Since we have previously reported another rat intestinal cDNA which encodes the C-terminus of a mucin-like peptide (MLP) [Xu, Wang, Huan, Cutz, Forstner and Forstner (1992) Biochem. J. 286, 335-338], we wished to discover whether M2 was encoded by the same gene. RNA blotting experiments with probes specific for M2 and MLP showed different mRNAs for each. The message for M2 (7.5-8.5 kb) was smaller than that for MLP (> 9.5 kb) and, unlike MLP, gave no signal in human colonic LS174T cells. The results of DNA blots probed with M2-798 and an MLP-probe suggest that M2 and MLP are likely to be single-copy genes. It would appear therefore that normal rat intestine, like human intestine, may express two different mucin genes.

The sea urchin egg receptor for sperm: isolation and characterization of the intact, biologically active receptor

The species-specific binding of sea urchin sperm to the egg is mediated by an egg cell surface receptor. Although earlier studies have resulted in the cloning and sequencing of the receptor, structure/function studies require knowledge of the structure of the mature cell surface protein. In this study, we report the purification of this glycoprotein to homogeneity from a cell surface complex of Strongylocentrotus purpuratus eggs using lectin and ion exchange chromatography. Based on the yield of receptor it can be calculated that each egg contains approximately 1.25 x 10(6) receptor molecules on its surface. The receptor, which has an apparent M(r) of 350 kD, is a highly glycosylated transmembrane protein composed of approximately 70% carbohydrate. Because earlier studies on the partially purified receptor and on a pure, extracellular fragment of the receptor indicated that the carbohydrate chains were important in sperm binding, we undertook compositional analysis of the carbohydrate in the intact receptor. These analyses and lectin binding studies revealed that the oligosaccharide chains of the receptor are sulfated and that both N- and O-linked chains are present. Functional analyses revealed that the purified receptor retained biological activity; it inhibited fertilization in a species-specific and dose-dependent manner, and polystyrene beads coated with it bound to acrosome-reacted sperm in a species-specific manner. The availability of biochemical quantities of this novel cell recognition molecule opens new avenues to studying the interaction of complementary cell surface ligands in fertilization.

Deglycosylation with trifluoromethanesulfonic acid differentially affects inhibitor activities of turkey ovomucoid

Turkey ovomucoid is an inhibitor of both trypsin and chymotrypsin. Treatment of this glycoprotein with trifluoromethanesulfonic acid in anisole resulted in time-dependent removal of carbohydrate and altered its biological activity. After 6 h of treatment the apparent molecular mass obtained by SDS-PAGE decreased from 38 to 30 kDa. Carbohydrate analyses indicated loss of 94% of original saccharide residues. The inhibitory activity of each domain was analyzed independently by comparing enzymic activity of trypsin and chymotrypsin in the absence of inhibitor to that preincubated in the presence of varying amounts of native or deglycosylated ovomucoid, respectively. The results demonstrated that removal of saccharides with trifluoromethanesulfonic acid differentially affects the inhibitor activities of turkey ovomucoid. Decreased inhibitory activity of the trypsin domain was observed with casein and benzoyl arginine ethyl ester as substrates. In contrast, enhanced inhibitory activity of the chymotrypsin domain was observed with benzoyl tyrosine ethyl ester and methyl-O-succinyl-Arg-Pro-Tyr-p-nitroanilide, good substrates for chymotrypsin, but not with casein.

Evidence for virus-encoded glycosylation specificity

Four spontaneously derived serologically distinct classes of mutants of the Paramecium bursaria chlorella virus (PBCV-1) were isolated using polyclonal antiserum prepared against either intact PBCV-1 or PBCV-1-derived serotypes. The oligosaccharide(s) of the viral major capsid protein and two minor glycoproteins determined virus serological specificity. Normally, viral glycoproteins arise from host-specific glycosylation of viral proteins; the glycan portion can be altered only by growing the virus on another host or by mutations in glycosylation sites of the viral protein. Neither mechanism explains the changes in the glycan(s) of the PBCV-1 major capsid protein because all of the viruses were grown in the same host alga and the predicted amino acid sequence of the major capsid protein was identical in the PBCV-1 serotypes. PBCV-1 antiserum resistance is best explained by viral mutations that block specific steps in glycosylation, possibly by inactivating glycosyltransferases.

Purification and fine characterization of a major allergen from Olea europaea pollen extract

Olea europaea (olive) pollen extract was prepared by aqueous extraction and characterized by biochemical and immunochemical methods. Two components, displaying respective mol. wt. of 17,000 and 19,000, were the most reactive allergens, being the doublet (designated Ole e I) recognized by most sera tested. The 19,000 mol. wt. component, purified by conventional biochemical procedure and lectin-affinity chromatography from the Ole e I doublet, was deglycosylated and analyzed by SDS-PAGE and by ELISA inhibition. The results obtained suggest that the 19,000 mol. wt. component represents the glycosylated form of the 17,000 component.

Complete structure of the tyrosine-linked saccharide moiety from the surface layer glycoprotein of Clostridium thermohydrosulfuricum S102-70

In this study, we have extended and completed a previous investigation (P. Messner, R. Christian, J. Kolbe, G. Schulz, and U. B. Sleytr, J. Bacteriol. 174:2236-2240, 1992) in which we demonstrated for the first time in prokaryotic organisms the presence of a novel O-glycosidic linkage via tyrosine. The surface layer glycoprotein of the eubacterium Clostridium thermohydrosulfuricum S102-70 is arranged in a hexagonal lattice, with center-to-center spacings of approximately 16.3 nm. Molecular weight determination by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of both glycosylated and chemically deglycosylated surface layer glycoprotein showed values for the monomeric subunits of 94,000 and 87,500, respectively. Glycopeptide fractions obtained after exhaustive pronase digestion of purified, intact glycoprotein were isolated by reversed-phase liquid chromatography. One- and two-dimensional nuclear magnetic resonance studies, together with chemical analyses and plasma desorption time-of-flight mass spectrometry, were used to elucidate the structure of the hexasaccharide moiety linked by the novel O-glycosidic linkage to tyrosine. The combined evidence suggests the following structure: beta-D-Galf-(1-->3)-alpha-D-Galp- (1-->2)-alpha-L-Rhap-(1-->3)-alpha-D-Manp-(1--3)-alpha-L- Rhap-(1-->3)-beta- D-Glcp-(1-->4)-L-Tyr.

Mucin-like glycoproteins in the equine embryonic capsule

The equine embryonic capsule replaces the zona pellucida and envelopes the conceptus during the second and third weeks of pregnancy. Although this capsule was described more than 100 years ago, its molecular structure has not been characterized. Here we present evidence that the glycoprotein(s) of the equine capsule resembles those of the mucin glycoprotein family. The resistance of the capsule to chemical and enzymatic solubilization was confirmed, and, as in mucins, protein constituted only 35-40% of its total dry mass. Determination of the sugar composition of the capsule using colorimetric assays and high-performance anion-exchange chromatography also showed it to have mucin-like characteristics. Gal, GalNAc, sulfated sugars, and sialic acid make up a high proportion of the capsular carbohydrate, while GlcNAc, Glc, and Man are minor components. These findings were verified using lectin histochemical staining of frozen sections of conceptuses. The results of amino acid analysis were also consistent with the proposal that the capsular glycoproteins belong to the mucin family. Removal of the covalently bound carbohydrate by beta-elimination under reducing conditions demonstrated that the capsule is O-glycosylated mainly on threonine residues. Affinity chromatography on jacalin-agarose confirmed that, like mucins, the capsular glycoproteins are heavily O-glycosylated. SDS-PAGE analysis revealed a prominent 21-kDa band, specific to the capsule, in preparations solubilized by trypsin but not by other proteases. Characterization of its constituent glycoprotein(s) should be helpful in elucidating the role of the capsule (and analogous blastocyst coverings in other species) during early pregnancy.

Isolation of a human biliary glycoprotein inhibitor of cholesterol crystallization

BACKGROUND

About 50% of populations in developed countries have bile supersaturated with cholesterol, which is a major risk factor for cholesterol gallstone formation. Despite the prevalence of supersaturated bile, only about 10% of these populations develop gallstones. The existence of a biliary protein that inhibits cholesterol crystallization was hypothesized to explain this discrepancy. This report outlines the purification and characterization of such a human biliary glycoprotein.

METHODS

Chromatographic methods were used for separation and characterization. Additional steps included activity analysis by crystal growth assay, electrophoresis, and deglycosylation.

RESULTS

The glycoprotein consists of a heterodimer, M(r) of 120 kilodalton, with subunits of M(r) of 63 kilodalton and 58 kilodalton. Each of the subunits is characterized by an isoelectric point of 6.6 and shows comparable inhibitory activity. Deglycosylation of the subunits show that they share a similar polypeptide backbone (M(r) of 35 kilodalton) based upon a highly similar amino acid profile. This suggests that differential subunit glycosylation alone may account for the apparent heterodimeric structure.

CONCLUSIONS

No other human biliary glycoprotein has been found thus far that shows cholesterol crystal growth-inhibiting activity. Thus, it may be of importance in preventing gallstone formation in healthy populations.

A monoclonal antibody that recognizes hyaluronic acid binding region of aorta proteoglycans

A chondroitin sulfate-dermatan sulfate proteoglycan was isolated from bovine aorta intima by extraction of the tissue with 4 M guanidine hydrochloride. The proteoglycan was purified by CsCl isopycnic centrifugation followed by gel filtration and ion exchange chromatography. A monoclonal antibody C8F4 was developed to this core protein. The characteristics and specificity of the antibody were studied by an enzyme-linked immunosorbent assay (ELISA) using an alkaline phosphatase conjugated antibody (goat anti-mouse IgG). The antibody binding to the core protein was found specific and optimal at pH 7.0. The antibody recognizes either intact chondroitin sulfate-dermatan sulfate proteoglycan monomer, chondroitinase ABC digested monomer or chemically deglycosylated proteoglycan. Free chondroitin sulfates, keratan sulfate and hyaluronic acid did not compete for the antigenic sites in ELISA. Limited hydrolysis of the core protein by trypsin resulted in three peptides and only the peptide with a molecular weight M(r) = 40,000 was found capable of binding to hyaluronic acid. The antibody C8F4 recognized this hyaluronic acid binding peptide but did not recognize the other two peptides suggesting that the epitope(s) for this antibody is in the hyaluronic acid-binding region of the core protein. The antibody recognized the core proteins from bovine nasal cartilage proteoglycan and human aorta proteoglycan but did not recognize bovine aorta link protein, bovine serum albumin, human serum albumin, human transferrin, collagen Type I and fibronectin. The antibody was found useful to localize proteoglycans in atherosclerotic lesions in human aorta by immunohistochemical techniques.

Self-aggregation of squid cranial cartilage proteoglycans

Squid cranial cartilage has been found to contain three different proteoglycan populations, two of which form aggregates (Vynios, D.H. and Tsiganos, C. P., Biochim. Biophys. Acta 1033: 139-147, 1990). The aggregation involves interaction of their protein cores as assessed by electron microscopy and biochemical data. Aggregating oligopeptides were isolated after mild trypsin digestion which inhibited self-aggregation of proteoglycans. The aggregation does not involve interaction of the side chains of polar amino acids and evidence is provided that it is mediated through hydrophobic interaction. It is enhanced upon concentration or incubation of the samples at 37 degrees C.

Cross-reactivity of sperm-binding proteins from chicken, turkey, and duck oocytes

Binding and penetration of spermatozoa through the perivitelline layer (PL) overlying the hen's ovum have been studied more frequently in the chicken than in other domesticated avian species. Species-specific action of the binding process was tested using an in vitro competition assay in which spermatozoa from the cock, tom, and drake were pretreated with solubilized PL protein (PL-P) from the chicken, turkey, and duck ovum. Spermatozoa were pretreated with PL-P for 20 min at 39 C and co-incubated in vitro with a .5 cm2 section of intact PL from the homologous sperm donor species for an additional 10 min at 39 C. Effectiveness of PL-P pretreatment was assessed quantitatively by the number of spermatozoa bound to the PL, and was expressed as a percentage of the control [minimum essential medium (MEM) pretreated sperm = 100%] binding. Pretreatment of cock spermatozoa with chicken, turkey, or duck PL-P resulted in 21, 40, and 48% binding, respectively. Similarly, pretreatment of tom spermatozoa with PL-P from chicken, turkey, or duck resulted in 45, 51, and 39% binding, and that of drake spermatozoa resulted in 38, 32, and 21% binding, respectively. Incubation of spermatozoa with PL-P from chicken, turkey, and duck ova indicated cross-reactivity and suppression of binding between avian spermatozoa and PL that was not species-specific.

Purification of two chitinases from Rhizopus oligosporus and isolation and sequencing of the encoding genes

Two chitinases were purified from Rhizopus oligosporus, a filamentous fungus belonging to the class Zygomycetes, and designated chitinase I and chitinase II. Their N-terminal amino acid sequences were determined, and two synthetic oligonucleotide probes corresponding to these amino acid sequences were synthesized. Southern blot analyses of the total genomic DNA from R. oligosporus with these oligonucleotides as probes indicated that one of the two genes encoding these two chitinases was contained in a 2.9-kb EcoRI fragment and in a 3.6-kb HindIII fragment and that the other one was contained in a 2.9-kb EcoRI fragment and in a 11.5-kb HindIII fragment. Two DNA fragments were isolated from the phage bank of R. oligosporus genomic DNA with the synthetic oligonucleotides as probes. The restriction enzyme analyses of these fragments coincided with the Southern blot analyses described above and the amino acid sequences deduced from their nucleotide sequences contained those identical to the determined N-terminal amino acid sequences of the purified chitinases, indicating that each of these fragments contained a gene encoding chitinase (designated chi 1 and chi 2, encoding chitinase I and II, respectively). The deduced amino acid sequences of these two genes had domain structures similar to that of the published sequence of chitinase of Saccharomyces cerevisiae, except that they had an additional C-terminal domain. Furthermore, there were significant differences between the molecular weights experimentally determined with the two purified enzymes and those deduced from the nucleotide sequences for both genes. Analysis of the N- and C-terminal amino acid sequences of both chitinases and comparison of them with the amino acid sequences deduced from the nucleotide sequences revealed posttranslational processing not only at the N-terminal signal sequences but also at the C-terminal domains. It is concluded that these chitinases are synthesized with pre- and prosequences in addition to the mature enzyme sequences and that the prosequences are located at the C terminal.

A novel keratan sulphate proteoglycan from a human embryonal carcinoma cell line

We describe here the purification and partial characterization of a 200 kDa keratan sulphate proteoglycan found in the pericellular matrix of human embryonal carcinoma cells. Previously we have shown that this molecule is recognized by a monoclonal antibody (GCTM-2). The antigen was isolated using ion-exchange chromatography and gel filtration, purification being monitored by e.l.i.s.a. using GCTM-2. Metabolic labelling of GCT 27 C-4 embryonal carcinoma cells with sodium [35S]sulphate resulted in the incorporation of [35S]sulphate into the purified molecule. Throughout the purification procedure, the peaks of 35S radioactivity were coincident with the peaks of immunoreactivity, and this label was released both by digestion with keratanase and chondroitinase, confirming the proteoglycan nature of the antigen. The intact molecule ran as a single broad band of 200 kDa, which has been identified by silver staining and immunoblotting following gel electrophoresis. Amino acid analysis of the purified antigen indicated a high content of serine, glycine and aspartic acid/asparagine residues. Visualization by rotary-shadowing electron microscopy suggests that the purified material forms large aggregates, even under denaturing conditions. Deglycosylation of this preparation with trifluoromethanesulphonic acid yielded a major band of 55 kDa and a minor band of 48 kDa. The biochemical nature of the molecule described here, along with tissue distribution studies using GCTM-2, indicates that the antigen is not related to previously described keratan sulphate proteoglycans.

Structure and metabolism of multiple heparan sulphate proteoglycans synthesized by the isolated rat glomerulus

Metabolism of biosynthetically [35S]sulphate-labelled heparan sulphate proteoglycan (HSPG) was studied in the isolated glomerulus. Chromatography and electrophoresis resolved HS into 5 components, designated HS1a, HS1b, and HS2 to HS4 in order of increasing Kd. Both HS1a (250 kDa) and HS1b (130 kDa) are present in the glomerular basement membrane and have glycosaminoglycan chains of 25-45 kDa. Chemical analysis of glycosaminoglycan chains indicated a similar content of 50% N-sulphation and 30% 6-O-sulphation on the hexosamine residues of all HSs, with the remaining 20% of sulphate likely at the 2-O-position of uronic acid residues. By pulse-chase analysis, the basement-membrane fraction was found to have a half-life of residency in the glomerulus of 37 h. Both HS1a and HS1b are mainly released intact into the medium and are not further broken down in that compartment. In contrast, HS2 is almost completely released into the medium immediately after synthesis and is not normally recovered from the tissue. It is a 90-kDa HSPG with a hydrophobic core protein and glycosaminoglycan chains similar in size to those of HS1. In addition to these larger PGs, HS3 and HS4 represent glycosaminoglycan chains with little or no core protein. HS1a, HS1b and HS2 were iodinated and deglycosylated. Each has a 30-kDa core protein in addition to 18 kDa of chondroitinase ABC- and nitrous-acid-resistant O-linked carbohydrate. This suggests the possibility of a single core protein with variable glycosylation and destination. HS1a has 5-6 glycosaminoglycan chains, HS1b 2-3 and HS2 1-2. We propose that basement-membrane HSPG (HS1a and HS1b) and a related, underglycosylated secreted HSPG (HS2) are the major HSPGs synthesized by the isolated glomerulus. Other molecular species may represent discrete steps in the turnover of basement-membrane HSPG.

Role of carbohydrate moieties in cross-reactivity between different components of Parietaria judaica pollen extract

Cross-reactivity between the different components in Parietaria judaica pollen extract has been investigated by polyclonal as well as monoclonal antibodies before and after chemical deglycosylation obtained by trifluoromethanesulphonic acid (TFMS) treatment of the extract. In western blotting a polyclonal rabbit antiserum, obtained by injecting purified Par j I, was able to recognise many components of the native extract. However, its reactivity was restricted, after chemical deglycosylation of the extract, to the major allergen alone, indicating that its cross-reactivity was due to sugar moieties. Moreover, out of several monoclonal antibodies raised by injecting the whole Parietaria judaica extract, one (1A4/2F8) was also able in western blotting to recognise an epitope shared by many components of the extract except the major allergen Par j I. However, in this case the broad reactivity of the antibody was not affected by the deglycosylating procedure. When the reactivity of Parietaria judaica extract was tested before and after sugar removal, against specific IgE from a pool of patient sera, no differences could be demonstrated, thus indicating that carbohydrates are not strongly involved in the binding of Parietaria judaica-specific IgE. The results indicate that both proteic and carbohydratic cross-reactive epitopes are shared by many components of Parietaria judaica pollen extract.

Vacuolar chitinases of tobacco: a new class of hydroxyproline-containing proteins

The fungicidal type I chitinases contribute to the defense response of plants against pathogens. Two tobacco chitinases represent a different class of hydroxyproline-containing proteins. Hydroxyproline-rich proteins are predominantly extracellular, structural glycoproteins proteins that lack enzymatic activity and contain many hydroxyproline residues. In contrast, type I chitinases are vacuolar enzymes. They are not glycosylated and contain a small number of hydroxyproline residues restricted to a single, short peptide sequence.

Structure of the glycan chain from the surface layer glycoprotein of Clostridium thermohydrosulfuricum L77-66

The thermophilic eubacterium Clostridium thermohydrosulfuricum L77-66 is covered by a crystalline surface layer composed of identical glycoprotein subunits which are arranged in a hexagonal lattice with centre-to-centre spacings of approx. 14.3 nm. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of cell wall preparations showed the presence of several broadened, carbohydrate-containing bands in a molecular mass range of 90 to 200 kDa. A total carbohydrate content of approx. 14% was determined in the purified surface layer glycoprotein. Chemical deglycosylation of this material by trifluoromethanesulfonic acid resulted in the disappearance of the complex banding pattern. Only a single band with a molecular mass of 82 kDa remained visible upon Coomassie staining. After proteolytic digestion of the surface layer glycoprotein a single glycopeptide fraction with an apparent molecular mass of approx. 25 kDa was obtained by gel filtration. Composition analysis, methylation, periodate oxidation and a combination of homonuclear and 1H-detected heteronuclear shift-correlated nuclear magnetic resonance experiments established the following structure for the glycan chain of the surface layer glycoprotein.

Crystallization and preliminary X-ray study of minor glucoamylase from Aspergillus awamori variant X-100/D27

Crystals of the reduced form of glucoamylase were obtained from polyethylene glycol 6000 solution by the hanging-drop method. The protein was treated with alpha-mannosidase to partly remove the sugar component. The crystals belong to the space group P2(1)2(1)2(1) with cell dimensions a = 116.7 A, b = 104.3 A, c = 48.5 A and diffract beyond 2.5 A resolution.

Structure of the axonal surface recognition molecule neurofascin and its relationship to a neural subgroup of the immunoglobulin superfamily

The chick axon-associated surface glycoprotein neurofascin is implicated in axonal growth and fasciculation as revealed by antibody perturbation experiments. Here we report the complete cDNA sequence of neurofascin. It is composed of four structural elements: At the NH2 terminus neurofascin contains six Ig-like motifs of the C2 subcategory followed by four fibronectin type III (FNIII)-related repeats. Between the FNIII-like repeats and the plasma membrane spanning region neurofascin contains a domain 75-amino acid residues-long rich in proline, alanine and threonine which might be the target of extensive O-linked glycosylation. A transmembrane segment is followed by a 113-amino acid residues-long cytoplasmic domain. Sequence comparisons indicate that neurofascin is most closely related to chick Nr-CAM and forms with L1 (Ng-CAM) and Nr-CAM a subgroup within the vertebrate Ig superfamily. Sequencing of several overlapping cDNA probes reveals interesting heterogeneities throughout the neurofascin polypeptide. Genomic Southern blots analyzed with neurofascin cDNA clones suggest that neurofascin is encoded by a single gene and its pre-mRNA might be therefore alternatively spliced. Northern blot analysis with domain specific probes showed that neurofascin mRNAs of about 8.5 kb are expressed throughout development in embryonic brain but not in liver. Isolation of neurofascin by immunoaffinity chromatography results in several molecular mass components. To analyze their origin the amino-terminal sequences of several neurofascin components were determined. The NH2-terminal sequences of the 185, 160, and 110-135 kD components are all the same as the NH2 termini predicted by the cDNA sequence, whereas the other neurofascin components start with a sequence found in a putative alternatively spliced segment between the Ig- and FNIII-like part indicating that they are derived by proteolytic cleavage. A combination of enzymatic and chemical deglycosylation procedures and the analysis of peanut lectin binding reveals O- and N-linked carbohydrates on neurofascin components which might generate additional heterogeneity.

Molecular characterisation and structural relationship of the synapse-enriched glycoproteins gp65 and gp55

gp65 and gp55 are glycoprotein components of CNS synapses that are recognised by a single monoclonal antibody, SMgp65. This antibody has now been used to investigate the molecular properties of these two glycoproteins and the structural relationship between them. Both gp65 and gp55 occur in most brain regions as doublets of apparent molecular masses of 63 and 67 kDa, and 52 and 57 kDa, respectively. Striatal samples, however, are enriched in a novel gp65 isoform of 69 kDa. Removal of oligosaccharide residues from gp65 and gp55 with trifluoromethanesulphonic acid shows that gp65 and gp55 are composed of single polypeptide chains of 40 and 28 kDa, respectively. Removal of sialic acid residues with neuraminidase lowers the apparent molecular mass of both glycoproteins by 5-6 kDa. Triton X-114 phase partitioning and alkaline extraction of synaptic membranes indicate that both gp65 and gp55 are integral membrane glycoproteins. Treatment of synaptic membranes with phosphatidylinositol-specific phospholipase C does not solubilise either glycoprotein. One-dimensional peptide and epitope maps obtained by digestion of gp65 and gp55 with endoproteinase lys C or subtilisin are consistent with a close structural relationship between the two molecules. Tryptic digestion of samples enriched in gp65 and/or gp55 results in the formation of a novel immunoreactive 53-kDa species that is resistant to further trypsin degradation except in the presence of 0.1% (wt/vol) sodium dodecyl sulphate. Trypsin treatment of cultures of forebrain neurones in situ lowers the apparent molecular mass of gp65 to 53 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Chitin-binding proteins in potato (Solanum tuberosum L.) tuber. Characterization, immunolocalization and effects of wounding

Tubers of potato (Solanum tuberosum L.) contain a number of chitin-binding proteins which have possible functions in defence against pathogens. A major protein of the tuber is the chitin-binding lectin which has been further characterized with respect to its antigenicity and N-terminal amino acid sequence. By using an antiserum monospecific for tuber lectin in unwounded potato the protein was found in the cytoplasm and vacuole, unusually for a hydroxyproline-rich glycoprotein, but consistent with its soluble nature in subcellular extracts. Little increased synthesis of the lectin precursor or the post-translationally modified form could be demonstrated in excised potato tuber discs. However, after wounding there is increased synthesis of another hydroxyproline-containing glycoprotein of Mr 57,000, which binds to chitin and shares common epitopes with the lectin. In comparison with the tuber lectin, this novel glycoprotein contains less hydroxyproline, but from its overall composition it is clearly not an underhydroxylated form of the tuber lectin. It differed in its N-terminal amino acid sequence and was much less glycosylated, although arabinose was still present. Synthesis of the Mr-57,000 polypeptide began after the initial burst of protein synthesis and increased, reaching a peak at 24 h after wounding. The protein was produced with its enzymes of post-translational modification, prolyl hydroxylase and arabinosyltransferase, concomitantly with the marker enzymes for wounding, phenylalanine ammonia-lyase and membrane-bound phenol oxidase and peroxidase.

Isolation and characterization of isolectins from Erythrina variegata seeds

Three isolectins were isolated from seeds of Erythrina variegata (Linn.) var. Orientalis by ion-exchange chromatography, followed by affinity chromatography on lactose-Sepharose 4B and acid-treated Sepharose 4B columns. The purified isolectins (EVLI, EVLII and EVLIII) are all specific for galactopyranosides and N-acetylgalactosamine, and their affinities for simple sugars are EVLIII greater than EVLII greater than EVLI. EVLI and EVLIII are homodimers made up of an A-subunit of molecular mass 36,000 and a B-subunit of molecular mass 33,000, whereas EVLII is a heterodimer composed of the A- and B-subunits. Upon treatment with trifluoromethansulphonic acid, the molecular masses of both subunits decreased to 31,000. Rechromatography of EVLII on the acid-treated Sepharose 4B column again produced the homodimeric lectins (EVLI and EVLIII). It is suggested that the constituent subunits of Erythrina variegata isolectins are eschangeable with each other in vitro.

Leucine aminopeptidase from Arabidopsis thaliana. Molecular evidence for a phylogenetically conserved enzyme of protein turnover in higher plants

Leucine aminopeptidases are exopeptidases which are presumably involved in the processing and regular turnover of intracellular proteins; however, their precise function in cellular metabolism remains to be established. Towards this goal, a full-length complementary DNA encoding a plant leucine aminopeptidase was isolated from a cDNA library of Arabidopsis thaliana and sequenced. The nucleotide sequence showed 49.5% identity to the Escherichia coli xerB-encoded leucine aminopeptidase. Sequence analysis revealed that the cDNA encodes a polypeptide of 520 amino acids with a calculated molecular mass of 54,506 Da. The C-terminal part (amino acids 200-520) of the deduced amino acid sequence showed 43.8% sequence identity to the xerB-encoded leucine aminopeptidase and 42.6% sequence identity to the amino acid sequence of bovine lens leucine aminopeptidase (EC 3.4.11.1). No sequence similarity (not even over short sequence elements) was observed with any other known peptidase or proteinase sequence. The cDNA was expressed as a fusion protein from the lacZ promoter in E. coli. Enzymatic analysis proved that the cloned cDNA encoded an active leucine aminopeptidase. The properties of this enzyme, including metal requirements, inhibitor sensitivity, pH optimum and the remarkable temperature stability, are very similar to those reported for leucine aminopeptidases from other tissues. Amino acids involved in metal and substrate binding in bovine lens aminopeptidase are completely conserved in the plant enzyme as well as in the XerB protein. Our results show that leucine aminopeptidases form a superfamily of highly conserved enzymes, spanning the evolutionary period from the bacteria to animals and higher plants. This is the first aminopeptidase cloned from a plant.

Glycosylation variants of endopeptidase-24.11 ('enkephalinase')

Anion exchange chromatography resolves two charge variants of rat kidney endopeptidase-24.11 (designated NEP 1 and NEP 2); each was purified to homogeneity using immunoaffinity chromatography. In addition to charge differences the subunit molecular weights of NEP 1 and NEP 2 differ and are 89 and 96 kDa, respectively. Isoelectric focusing resolved 8-10 pl species in the pH range of 5.95-6.20 for NEP 1 and 5.46-6.06 for NEP 2. Removal of sialic acid residues converted the multiple pl species to one form with a pl of 6.32 for NEP 2, and two forms with pls of 6.27 and 6.32 for NEP 1. Endoglycosidase H or F, capable of removing high-mannose and biantennary branched N-linked oligosaccharides, produced a 2-3 kDa decrease in the molecular weight of both NEP 1 and NEP 2. Peptide-N-glycosidase F, capable of removing all classes of N-linked oligosaccharides, produced 8 and 11 kDa decreases in NEP 1 and NEP 2, respectively. Removal of all N-linked and O-linked oligosaccharides with trifluoromethanesulfonic acid resulted in 10 and 15 kDa decreases in NEP 1 and NEP 2, respectively. Tryptic epitope maps demonstrated that NEP 2 was cleaved at a slower rate than NEP 1. These analyses demonstrate that rat kidney NEP exhibits sialic acid microheterogeneity resulting in two distinct change variants. The data also indicate that NEP 2 contains more N- and O-linked carbohydrate mass than NEP 1 and may contain a larger polypeptide backbone giving rise to molecular weight differences between these enzyme forms.

Molecular characterization of interleukin 12

Interleukin 12 (IL-12), formerly known as cytotoxic lymphocyte maturation factor and natural killer cell stimulatory factor, is a cytokine secreted by a human B lymphoblastoid (NC-37) cell line when induced in culture with phorbol ester and calcium ionophore. This factor has been purified to homogeneity and shown to synergize with low concentrations of interleukin 2 in causing the induction of lymphokine-activated killer cells. In addition, purified IL-12 stimulated the proliferation of human phytohemagglutinin-activated lymphoblasts by itself and exerted additive effects when used in combination with suboptimal amounts of interleukin 2. The protein is a heterodimer composed of a 40- and a 35-kDa subunit. Amino acid sequence analysis confirmed predicted sequences from the cloned cDNAs of each subunit. Chemical and enzymatic deglycosylation of the heterodimer demonstrated that the 40- and 35-kDa subunits contain 10 and 20% carbohydrate, respectively. Structural analysis of IL-12 using site-specific chemical modification revealed that intact disulfide bonds are essential for bioactivity. The 40-kDa subunit of IL-12 was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and confirmed by immunoblotting as being present in NC-37 cell supernatant solutions in relatively large amounts uncomplexed to the 35-kDa subunit. Previously it had been shown that the 40-kDa subunit alone does not cause the proliferation of activated human T lymphocytes or enhance the cytolytic activity of human natural killer cells. However, results obtained by site-specific chemical modification suggesting that a tryptophan residue is at or near the active site of IL-12 may imply a direct role of the subunit in interacting with the IL-12 receptor. These data may support the recent proposal (D.P. Gearing and D. Cosman (1991) Cell 66, 9-10) that IL-12 consists of a complex of cytokine and soluble receptor.

Polypeptide N-acetylgalactosaminyltransferase activity in tracheal epithelial microsomes

Pig tracheal epithelium, a site of extensive mucin biosynthesis, contained polypeptide N-acetylgalactosaminyltransferase activity directed towards L-threonine residues. The enzyme preparation was broadly similar in properties to preparations from other tissues, e.g. pig and bovine submaxillary glands, bovine colostrum, BW5147 mouse lymphoma and baby-hamster kidney cells. Enzyme was membrane-bound and was released from microsomal preparations by extraction with Triton X-100. Extracted enzyme had a pH optimum of 7.5, had a requirement for Mn2+ (10 mM) and was inhibited by Na2EDTA. The Km for UDP-N-acetylgalactosamine was 110 microM and that for an octapeptide acceptor (VTPRTPPP) was 3.0 mM at 37 degrees C. Using a range of synthetic peptides of known structure related to TPPP it was established that L-threonine residues were specifically O-glycosylated probably in the alpha-configuration. Synthetic peptides containing the TPPP sequence required a peptide length of five or more for significant acceptor activity. In VTPRTPPP the two threonine residues were similarly glycosylated, as revealed by tryptic cleavage of the glycosylated product and separation of the 3H-labelled fragments. The enzyme preparation also specifically catalysed the transfer of N-acetylgalactosaminyl residues from UDP-N-acetyl[1-3H]galactosamine to bovine submaxillary mucin core protein and to myelin basic protein.

Binding of Pseudomonas cepacia to normal human intestinal mucin and respiratory mucin from patients with cystic fibrosis

Although not as prevalent as Pseudomonas aeruginosa, Pseudomonas cepacia is another opportunistic pathogen which colonizes the lungs of at least some patients with cystic fibrosis. A subgroup of these patients exhibits the "cepacia syndrome", i.e., a rapid clinical deterioration and death within one year. To investigate potential early sites of bacterial attachment, we have measured the specific binding of P. cepacia isolates from cystic fibrosis (CF) sputa to both CF and non-CF mucins purified from respiratory and intestinal secretions, respectively. As shown in microtiter binding assays, clinical isolates from 19/22 patients were found to bind to both mucins, with the highest specific binding exhibited by isolates from eight patients, seven of whom later died with the cepacia syndrome. No differences were observed in the binding capacity of the two (CF versus non-CF) mucins. Binding was specific, saturable, and not influenced by tetramethylurea, a disruptor of hydrophobic associations. Individual sugars were ineffective as hapten inhibitors, as were several lectins. Mucins treated by reduction/alkylation or chloroform/methanol extraction showed enhanced bacterial binding, findings which were attributed to exposure of underlying binding sites. Deglycosylation procedures indicated that mucin receptors for P. cepacia include N-acetylglucosamine and N-acetylgalactosamine, probably linked together as part of core oligosaccharide structures. P. cepacia isolates also bound to buccal epithelial cells, and mucin partially inhibited the binding of those isolates of P. cepacia that also had the ability to bind to mucin. We speculate that specific binding of P. cepacia to secreted mucins may be an early step in the pathogenesis of the cepacia syndrome.

Purification and characterization of a soluble beta-fructofuranosidase from Daucus carota

Soluble beta-fructofuranosidase with an intracellular location and an isoelectric point of 3.8 (isoenzyme I) was purified and characterized from dry seeds and seedlings of carrot (Daucus carota). The enzyme hydrolyzed sucrose with a Km of 5 mM and a broad pH optimum around 5.0. The purified protein, which was N-glycosylated with high-mannose-containing and high-xylose-containing complex glycans, eluted as a monomeric polypeptide with a molecular mass of 68,000 from a gel-filtration column. On SDS/PAGE, the protein separated in the presence of SDS and 2-mercaptoethanol into three polypeptides with molecular masses of 68, 43 and 25 kDa. The amount of the 68-kDa polypeptide was highest in dry seeds and decreased with increasing age of carrot seedlings. Amino acid sequence analysis and immunological studies showed that the 43-kDa and 25-kDa polypeptides were N-terminal and C-terminal proteolytic fragments of the 68-kDa polypeptide. A comparison of partial amino acid sequences of the soluble beta-fructofuranosidase with the complete sequence of carrot cell-wall beta-fructofuranosidase showed that their N-terminal sequences were different, whereas some of the internal tryptic peptide sequences were up to 70% identical.

Production of active Bacillus licheniformis alpha-amylase in tobacco and its application in starch liquefaction

As a first example of the feasibility of producing industrial bulk enzymes in plants, we have expressed Bacillus licheniformis alpha-amylase in transgenic tobacco, and applied the seeds directly in starch liquification. The enzyme was properly secreted into the intercellular space, and maximum expression levels of about 0.3% of total soluble protein were obtained. No apparent effect of the presence of the enzyme on plant phenotype was observed. The molecular weight of the enzyme produced in tobacco was around 64 kD. The difference, compared to 55.2 kD for the bacterial enzyme, was found to result from complex-type carbohydrate chains attached to the protein. Application studies on the liquefaction of starch were done with transgenic seeds containing the recombinant alpha-amylase. The resulting hydrolysis products were virtually identical with those obtained from degradation with alpha-amylase from Bacillus licheniformis.

Mapping of monoclonal antibody binding sites on CNBr fragments of the S-layer protein antigens of Rickettsia typhi and Rickettsia prowazekii

The 120 kDa surface protein antigens (SPAs) of typhus rickettsiae lie external to the outer membrane in regular arrays and chemically resemble the S-layer proteins of other bacteria. These proteins elicit protective immune responses against the rickettsiae. In order to study the immunochemistry of these proteins, purified SPAs from Rickettsia typhi and Rickettsia prowazekii were fragmented with CNBr. The fragments were separated by SDS-PAGE and were recovered on PVDF membrane following electroblotting. The origin of eight major fragments from R. prowazekii and seven major fragments from R. typhi was determined by automated N-terminal amino acid sequencing and by comparison with the DNA sequence encoding R. prowazekii SPA. The cleavage patterns and protein sequences of the two proteins differed significantly. CNBr fragments corresponding to the C-terminus (amino acid 1372-1612 of the deduced sequence from encoding gene spaP) were not present in both SPAs. This suggests that the corresponding C-terminal region was not synthesized or was removed during SPA translocation to the cell surface. Modified amino acids were detected in each protein. Eighteen monoclonal antibodies selected for varied reactivity with both native and denatured SPA proteins could be classified into eight different types based on western blot analysis of the CNBr fragments. Six of the monoclonal antibody types reacted predominantly with a single region of the SPAs. Two types of antibodies bound to several CNBr fragments which contained both limited sequence similarity and modified amino acids either of which might account for the multisite binding of these antibodies.

Isolation and expression of a gene which encodes a wall-associated proteinase of Coccidioides immitis

A chymotrypsinlike serine proteinase of Coccidioides immitis with an estimated molecular size of 34 kDa has been shown by immunoelectron microscopy to be associated with the walls of the parasitic cells of this human respiratory pathogen. The proteinase has been suggested to play a role in spherule development. We report the isolation of a 1.2-kb cDNA from an expression library of C. immitis constructed in the lambda ZAP II phage vector. The cDNA is suggested to encode the 34-kDa protein. We demonstrate identity between segments of the deduced amino acid sequence of the open reading frame of the 1.2-kb cDNA and three distinct sequences obtained from cyanogen bromide cleavage peptides of the purified proteinase. The occurrence of N-glycosyl linkage sites in the deduced sequence of 309 amino acids of the open reading frame (ORF) correlates with our identification of such linkage sites in the native glycosylated proteinase. A protein encoded by an 800-bp fragment of the 1.2-kb cDNA, which was produced by transformed Escherichia coli XL1-Blue, was recognized by the anti-34-kDa protein antibody in a Western blot (immunoblot). Northern (RNA) hybridization of total poly(A)-containing RNA of C. immitis with the labeled 1.2-kb cDNA clone revealed a single band of approximately 1.75 kb. Partial homology was demonstrated between the deduced amino acid sequence of the ORF (927 bp) and reported sequences of alpha-chymotrypsin and chymotrypsinogens. Expression of the proteinase gene was examined by Northern dot blot analysis of total RNA from different stages of parasitic cell development in C. immitis. Maximum levels of specific mRNA were detected during early endospore wall differentiation. The 34-kDa proteinase appears to be concentrated in walls of the parasitic cells at stages of active growth. We suggest that the enzyme may participate in wall plasticization and/or intussusception or in cell wall turnover.