Isolation and partial characterization of nigrin b,a non-toxic novel type 2 ribosome-inactivating protein from the bark ofSambucus nigra L.

The bark ofSambucus nigra L. contains a non-toxic novel type 2 ribosome-inactivating protein that we named nigrin b.In vitro, nigrin b strongly inhibited mammalian protein synthesis but did not affect plant nor bacterial protein synthesis. The protein (M _r 58 000) contains two subunits, A (M _r 26 000) and B (M _r 32 000); linked by disulphide bridge(s). Nigrin b was found to be an rRNA N-glycosidase of the rRNA of intact mammalian ribosomes and shares a very good N-terminal amino-acid sequence homology with the anti-HIV-1 proteins TAP 29 and trichosanthin.     

Properties of γ-aminobutyraldehyde dehydrogenase from Escherichia coli

γ-Aminobutyraldehyde dehydrogenase from Escherichia coli K-12 has been purified and characterized from cell mutants able to grow in putrescine as the sole carbon and nitrogen source. The enzyme has an M_r of 195 000±10 000 in its dimeric form with an M_r of 95 000±1000 for each subunit, a pH optimum at 5.4 in sodium citrate buffer, and does not require bivalent cations for its activity. K_m values are 31.3±6.8 μM and 53.8±7.4 μM for Δ-1-pyrroline and NAD⁺, respectively. An inhibitory capacity for NADH is also shown using the purified enzyme.     

Characterization and cellular localization by monoclonal antibodies of the 60 kDa mannose specific lectin of human promyelocytic cells,HL60

Myelomonocytic lineage cells express anM _r 60 000 mannose specific lectin, MR60 (Pimpaneauet al. (1991),Carbohydr Res 213: 95–108). Under non-reducing conditions, this protein migrates as a 120 000 protein. MR60 does not contain anyN-glycan moiety cleavable by the action ofN-glycanase. MR60 induces a sugar selective aggregation of beads coated with glycosylated albumin: beads bearing -d-mannosyl residues are aggregated while beads bearing -d-glucosyl residues are not. A monoclonal antibody Lec101B, specific for MR60, recognizes a singleM _r 60 000 protein by Western blotting. This monoclonal antibody does not label the cell surface of cells expressing MR60, but decorates intracellular vesicles upon permeabilization of these cells.     

Variation in endoplasmic-reticulum-associated glycoproteins of carrot cells cultured in vitro

Glycoproteins extracted from microsomes of in-vitro-cultured cells of Daucus carota L. cv. US-Harumakigosun were analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and detected by peroxidase-conjugated concanavalin A. The appearance of a glycoprotein with M_r 31 000 (GP 31) was correlated with the ability of cells to form somatic embryos. GP 31 appeared in embryogenic cells cultured in 2,4-dichlorophenoxyacetic acid (2,4-D)-containing medium, but not in somatic embryos and non-embryogenic cells; it disappeared when the cultures were transferred to auxin-free medium. Another glycoprotein with M_r 32 000 (GP 32) was detected only in non-embryogenic cells, regardless of the presence or absence of 2,4-D. Both glycoproteins, GP 31 and GP 32, were associated with the rough endoplasmic reticulum and were extractable with 0.05% deoxycholate.Abbreviations Con A concanavalin A - 2,4-D 2,4-dichlorophenoxyacetic acid - ER endoplasmic reticulum - GP 31, GP 32 a glycoprotein with an apparent molecular mass of 31 or 32 kdalton - kDa kilodalton - MS Murashige and Skoog - M_r apparent molecular mass - SDS-PAGE sodium dodecylsulfate-polyacrylamide gel electrophoresis     

Wheat-germ agglutinin is synthesized as a glycosylated precursor

The biosynthesis and processing of wheat-germ agglutinin (WGA) were studied in developing wheat (Triticum aestivum L. cv. Marshall) embryos using pulse-chase labeling, subcellular fractionation and immunocytochemistry. A substantial amount of newly synthesized WGA was organelle-associated. Isolation of WGA on affinity columns of immobilized N-acetylglucosamine indicated that it was present in a dimeric form. When extracts from embryos pulse-labeled with [³⁵S]cysteine were fractionated on an isopycnic sucrose gradient, radioactivity incorporated into WGA was detected at a position coincident with the endoplasmic reticulum (ER) marker enzyme NADH-cytochromec reductase. The WGA in the ER could be slowly chased into the soluble, vacuolar fraction, with a half-life of approx. 8 h. Immunolocalization studies demonstrated the accumulation and distribution of WGA throughout the vacuoles.Four forms of the WGA monomer were characterized using immunoaffinity purification and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In-vitro translation of polyadenylated RNA isolated from developing wheat embryos produced a polypeptide with M_r 21 000. In-vivo labeling of embryos with radioactive amino acids resulted in the formation of a polypeptide of M_r 23 000 and the mature monomer of M_r 18000. When [³H]mannose was used in labeling studies, only the polypeptide of M_r 23 000 was detected. In-vivo labeling in the presence of tunicamycin yielded an additional polypeptide of M_r 20 000. These results indicate that WGA is cotranslationally processed by the removal of a signal peptide and the addition of a glycan, presumably at the carboxy-terminus (N.V. Raikhel and T.A. Wilkins, 1987, Proc. Natl. Acad. Sci. USA 84, 6745–6749). The glycosylated precursor of WGA is post-translationally processed to the mature form by the removal of a carboxyl-terminal glycopeptide.Abbreviations ER endoplasmic reticulum - IgG immunoglobulin G - M_r relative molecular mass - poly(A)⁺RNA polyadenylated RNA - SDS-PAGE sodium dodecyl sulfatepolyacrylamide gel electrophoresis - WGA wheat-germ agglutinin     

Purification of an elicitor-induced glucan synthase (callose synthase) from suspension cultures of French bean (Phaseolus vulgaris L.): purification and immunolocation of a probable Mr-65 000 subunit of the enzyme

Membrane preparations from suspension-cultured cells of French bean (Phaseolus vulgaris L.) contained callose synthase (EC 2.4.1.34) activity which was preserved upon solubilisation. Following elicitor treatment of cell cultures, increased activity could be extracted and this increase was maintained during purification. The enzyme was purified by high-pressure liquid chromatography and active fractions showed a variable association of two polypeptides of relative molecular masses (M_r) 55 000 and 65 000, the latter being in excess. The M_r-65 000 polypeptide was purified to homogeneity and an antibody raised to it. This antibody showed complex effects on callose synthase activity when incubated with membrane and soluble extracts. In comparison with other systems, the M_r-55 000 subunit is likely to represent the catalytic subunit while the M_r-65 000 polypeptide is a possible regulatory subunit. The M_r-65 000 polypeptide was immunolocated in membranes at sites of callose synthesis in the plant, in cell plates, in sieve plates, at the plasma membrane-wall interface of wounded cells and in papillae in infected cells. Received: 18 January 1997 / Accepted: 8 May 1997     

Cloning and expression of theClostridium thermocellum celS gene inEscherichia coli

Clostridium thermocellum ATCC 27405 produces an extremely complicated multi-component cellulase aggregate (cellulosome) highly active on crystalline cellulose. From the cellulosome, two subunits, CelS (or S _s ;M _r = 82 000) and CelL (or S _l , CipA;M _r = 250 000), have been identified as essential for crystalline cellulose degradation [Wu et al. (1988) Biochemistry 27:1703]. We have determined the DNA sequence of thecelS gene from four cloned DNA fragments encompassing this gene [Wang et al. (1993) J Bacteriol 175:1293]. To express the entirecelS gene inEscherichia coli, thecelS structural gene was amplified by the polymerase chain reaction (PCR) employing the PCR primers corresponding to sequences flanking the desired gene. This PCR product (2.1 x 10³ bases; 2.1 kb) was cloned into anE. coli expression vector pRSET B. Subsequent expression of the cloned gene resulted in a fusion protein (rCelS;M _r = 86 000) as inclusion bodies. The rCelS protein was recognized specifically by an anti-CelS antiserum in a Western blot analysis. The inclusion bodies were purified and solubilized in 5m urea. The refolded rCelS produced very little reducing sugar from carboxymethylcellulose. However, it showed a higher activity on the crystalline cellulose (Avicel) and an even higher activity on phosphoricacid-swollen Avicel. These results indicate that the CelS is an exoglucanase.     

A new lectin from tulip (Tulipa) bulbs

A lectin was isolated from tulip (Tulipa) bulbs by affinity chromatography on fetuin-agarose and partially characterized. The tulip lectin is a tetrameric protein composed of four identical subunits of M_r 28 000, which are not held together by disulphide bonds. It is not glycosylated and has an amino-acid composition typified by a high content of asparagine-aspartic acid, leucine, glycine and serine. Tulip lectin agglutinates human red blood cells, but has a much higher specific activity with rabbit erythrocytes. In hapten-inhibition assays with the latter type of red blood cell the lectin exhibits a complex specificity, whereas its agglutination with human erythrocytes is readily inhibited by N-acetylgalactosamine, lactose, fucose and galactose.Abbreviations DEAE diethylaminoethyl - PBS phosphate-buffered saline - TL Tulipa lectin - M_r relative molecular mass - SDS-PAGE sodium dodecyl sulphate-polyacrylamide gel electrophoresis     

A nuclear protein associated with cell divisions in plants

A nuclear protein, present in carrot meristems and rapidly proliferating cultured cells of carrot (Daucus carota L.) has been identified by the use of a monoclonal antibody (MAb 21D7). By combining the techniques of two-dimensional polyacrylamide gel analysis and blotting separated proteins onto nitrocellulose sheets, it was shown that the antibody detected a single polypeptide of apparent molecular mass (M _r) of 45000 and an isoelectric focusing point (pI) of 6.7. This protein was found by subcellular fractionation and immunofluorescence to be highly concentrated in the nucleoli of somatic and zygotic embryos of a wide range of plants. It was not detectable in logarthmically growing cells ofEscherichia coli, yeast, embryos ofDrosophila melanogaster or cultured C3H mouse cells. These data indicate that this protein is a highly conserved non-histone protein associated with nuclei of rapidly dividing plant cells.Abbreviations M _r apparent molecular mass - Da dalton - Ig immunoglobulins - MAb monoclonal antibody - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - 2-D gel two-dimensional gel electrophoresis - 2,4-D 2,4-dichlorophenoxyacetic acid     

Identification of the insulin receptor in undifferentiated and differentiated NB-15 mouse neuroblastoma cells by affinity labeling

Plasma membranes prepared from clonal NB-15 mouse neuroblastoma cells were sequentially incubated with ¹²⁵I-labeled insulin (10 nM) and the bifunctional cross-linking agent disuccinimidyl suberate. This treatment resulted in the cross-linking of ¹²⁵I-labeled insulin to a polypeptide that gave an apparent M_r of 135 000 on a sodium dodecyl sulfate-polyacrylamide gel electrophoresed in the presence of 10% β-mercaptoethanol. Affinity labeling of this polypeptide was inhibited by the presence of 5 μM unlabeled insulin, but not by 1 μM unlabeled nerve growth factor. Using the same affinity labeling technique, ¹²⁵I-labeled nerve growth factor (1 nM) did not label any polypeptide appreciably in the plasma membranes of NB-15 cells but labeled an M_r 145 000 and an M_r 115 000 species in PC-12 rat pheochromocytoma cells. The number of insulin binding sites per cell in the intact differentiated NB-15 mouse neuroblastoma cells was approx. 6-fold greater than that in the undifferentiated NB-15 mouse neuroblastoma cells as measured by specific binding assay, suggesting an increase of the number of insulin receptors in NB-15 mouse neuroblastoma cells during differentiation.     

Subcellular distribution of carbonic anhydrase in Solanum tuberosum L. leaves

The intracellular compartmentation of carbonic anhydrase (CA; EC 4.2.1.1), an enzyme that catalyses the reversible hydration of CO₂ to bicarbonate, has been investigated in potato (Solanum tuberosum L.) leaves. Although enzyme activity was mainly located in chloroplasts (87% of total cellular activity), significant activity (13%) was also found in the cytosol. The corresponding CA isoforms were purified either from chloroplasts or crude leaf extracts, respectively. The cytosolic isoenzyme has a molecular mass of 255 000 and is composed of eight identical subunits with an estimated M _r of 30000. The chloroplastic isoenzyme (M _r 220000) is also an octamer composed of two different subunits with M _r estimated at 27 000 and 27 500, respectively. The N-terminal amino acid sequences of both chloroplastic CA subunits demonstrated that they were identical except that the M _r-27 000 subunit was three amino acids shorter than that of the M _r-27 500 subunit. Cytosolic and chloroplastic CA isoenzymes were found to be similarly inhibited by monovalent anions (Cl^–, I^–, N ₃ ^- and NO ₃ ^- ) and by sulfonamides (ethoxyzolamide and acetozolamide). Both CA isoforms were found to be dependent on a reducing agent such as cysteine or dithiothreitol in order to retain the catalytic activity, but 2-mercaptoethanol was found to be a potent inhibitor. A polyclonal antibody directed against a synthetic peptide corresponding to the N-terminal amino acid sequence of the chloroplastic CA monomers also recognized the cytosolic CA isoform. This antibody was used for immunocytolocalization experiments which confirmed the intracellular compartmentation of CA: within chloroplasts, CA is restricted to the stroma and appears randomly distributed in the cytosol.Abbreviations BSA bovine serum albumin - CA carbonic anhydrase - PMSF phenylmethylsulphonyl fluoride - BAM benzamidine - DTT dithiothreitol - 2-ME 2-mercaptoethanol - PVDF polyvinylidene difluoride The authors thanks P. Carrier and Dr. B. Dimon for technical assistance with the mass-spectrometry measurements.     

Isolation, characterization and protein and polar lipid compositions of Paracoccus denitrificans outer membrane

Sucrose density gradient centrifugation of Paracoccus denitrificans strains ATCC 13543 and ATCC 17741 cell envelopes plus poly-β-hydroxybutyrate, isolated from organisms broken using a French pressure cell, revealed three bands of densities: I, 1.16 g/ml; II, 1.19 g/ml; III, 1.24 g/ml. On the basis of chemical and enzymatic assays and sodium dodecyl sulfate-polyacrylamide gel electrophoresis the bands were identified as: I, cytoplasmic membrane; II, poly-β-hydroxybutyrate; III, outer membrane plus poly-β-hydroxybutyrate. Poly-β-hydroxybutyrate was removed by increased low-speed centrifugation before deposition of cell envelopes. Density gradient centrifugation of cell envelopes gave a simple pattern of two bands, cytoplasmic and outer membranes. In both strains outer membranes showed a broad protein band at M_r 70 000–83 000 upon SDS-polyacrylamide gel electrophoresis of samples solubilized at 25°C, which was not present in samples solubilized at 100°C, where a single major band was present of M_r 32 000 in strain ATCC 13543 and 35 000 in strain ATCC 17741. The major outer membrane protein stained positively for lipid in both strains, as did an M_r 70 000 protein, which was the second major protein in strain ATCC 17741. The second major outer membrane protein of stain ATCC 13543 had an M_r of 20 000 in unheated samples but 23 000 in heated samples. This protein was not present in strain ATCC 17741. Quantitative data on the polar lipid compositions of cell envelope fractions are presented.     

Affinity labeling of high-affinity α-thrombin binding sites on the surface of hamster fibroblasts

The serine proteinase α-thrombin potently stimulates reinitiation of DNA synthesis in quiescent Chinese hamster fibroblasts (CCL39 line). ¹²⁵I-labeled α-thrombin binds rapidly and specifically to CCL39 cells with high affinity (K_d ≈ 4 nM). Binding at 37°C was found to remain stable for 6 h or more during which time no receptor down-regulation, ligand internalization and/or degradation could be detected. The structure of α-thrombin receptors on CCL39 cells was identified by covalently coupling ¹²⁵I-α-thrombin to intact cells using a homobifunctional cross-linking agent, ethylene glycol bis(succinimidyl succinate). By resolution in sodium dodecyl sulfate polyacrylamide gel electrophoresis we observed the specific labeling of a major α-thrombin-binding site of M_r ≈ 150 000 revealed as a ¹²⁵I-α-thrombin cross-linked complex of M_r ≈ 180 000. Independent of chemical cross-linking, ¹²⁵I-α-thrombin also formed a covalent complex with a minor, 35 000 M_r, membrane component identified as protease nexin. Two derivatives of α-thrombin modified at the active site are 1000-fold less than α-thrombin for mitogenicity. These two non-mitogenic derivatives bound to cells with similar affinity and maximal binding capacity as native α-thrombin, and affinity-labeled the receptor subunit of M_r 150 000. When present in large excess, during incubation of cells with α-thrombin, these binding antagonists were ineffective in blocking α-thrombin-induced DNA synthesis. These data suggest that the specific 150 000 M_r binding sites that display high affinity for α-thrombin do not mediate induction of the cellular mitogenic response.     

Nucleotide sequence of a cDNA clone encoding the precursor of the peridinin-chlorophyll a-binding protein from the dinoflagellate Symbiodinium sp.

mRNA from the dinoflagellate Symbiodinium sp. isolated from the staghorn coral Acropora formosa was used for the construction of cDNA libraries. A cDNA clone was identified which encoded the precursor of peridinin-chlorophyll a-binding protein (PCP), including a 52 amino acid transit peptide and the 313 amino acid mature protein. The deduced amino acid sequence clearly contains an internal duplication, implying that amongst dinoflagellates the M _r 35 000 form of PCP has arisen by duplication and fusion of genes encoding the M _r 15 000 form. This is the first reported sequence of a dinoflagellate light-harvesting protein. The anatomy of the mature protein and the transit peptide are discussed.Abbreviations PCP peridinin-chlorophyll a-binding protein; cab, chlorophyll a/b-binding protein - LHC light-harvesting complex - FCP fucoxanthin-chlorophyll a/c-binding protein     

Structure and expression of the mouse homologue of the XK gene

 The human Kx blood group antigen is carried by a 37 000 M _r apparent molecular mass membrane polypeptide which is deficient in rare individuals with the McLeod syndrome. The X-linked human XK gene is transcribed in many tissues including adult skeletal muscle and brain, sieges of disorders observed in McLeod syndrome. We report here the cloning of the orthologous mouse XK mRNA. Comparison of XK from human and mouse revealed 80% sequence similarity at the amino acid level. The mouse XK gene is organized in two exons and is expressed in many tissues, but its expression pattern is slightly different from that of the human gene. The presence in mouse erythrocyte membrane of a 43 000 M _r Kx-related protein was demonstrated by immunoblotting with a rabbit antiserum directed against the human protein. With non-reduced samples, a 140 000 M _r species was detected instead of the 43 000 M _r protein, suggesting that, as demonstrated in the Kx polypeptide might be complexed with another protein in mouse red cells, presumably the homologue of the human Kell protein of 93 000 M _r. Received: 22 February 1999 / Revised: 8 June 1999     

Characteristics of intracellular proteolytic activities ofBacillus megaterium

Intracellular proteolytic activities ofB. megaterium KM occur soluble in the cytoplasm and periplasm and insoluble in the membrane. Two proteolytic enzymes were found in the cytoplasmic fraction by gel filtration on Sephadex G 150 and by polyacrylamide gel electrophoresis. The first enzyme called C_I was stable, had a relative molecular mass ofM _r=105000 (M=105 kg/mol) and was inhibited by EDTA and PMSF, whereas the second, designated C_II, was labile and had a relative molecular mass ofM _r=46000 (M=46 kg/mol). Because of its lability it could not be characterized in detail. In the “periplasm” only a single proteolytic enzyme P (M _r=28000;M=28 kg/mol) inhibited by EDTA could be demonstrated. The extracellular enzyme exhibited similar properties. The membrane proteolytic activity was sensitive to PMSF and EDTA. The membrane enzymes have not yet been solubilized. In cells of the mutant KM 12 that does not produce the extracellular proteinase, only one type of proteinase, in all its properties identical with the cytoplasmic proteinase C_I, could be demonstrated.     

Selected low-cohesion variants of Actinobacillus actinomycetemcomitans and Haemophilus aphrophilus lack distinct antigens recognized by human antibodies

Actinobacillus actinomycetemconitans OMZ 346 A and Haemophilus aphrophilus OMZ 384 A, isolated on a synthetic selective and differentiating agar, show the highly cohesive and wall adherent growth in liquid medium which is typical for all primary oral isolates of these species. From each of them a low cohesion variant, OMZ 346 F and OMZ 384 F, respectively, was obtained by selection for cells growing in suspension. Screening of Western blots of these four strains with several human sera revealed the loss of a 4000 M_r antigen in both F strains. Human antibodies bound to the 400 M_r band material on preparative Western blots of the A strains were cluted with 4M magnesium chloride. These antibodies showed no cross-reaction between the 4000 M_r material of the two closely related species.     

Identification and characterization of a mouse cell surface antigen with alternative molecular forms

We present the characterization of a new mouse cell surface protein, recognized by the 3138-specific monoclonal antibody. The expression of this antigen is predominantly restricted to the hematopoietic and lymphoid tissues: bone marrow, spleen, lymph node, and thymus. Immunoblot analyses show that the 3138 determinant is present on molecules with different apparent relative masses. The 3138 antigen migrates on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band of M _r 115 000 for normal nonstimulated spleen cells and thymocytes and as two bands of M _r 115 000 and M _r 125 000 for bone marrow cells and mitogen-stimulated spleen cells. The multiple sizes of the 3138 antigens (isoforms) found on various cell lines are not due to allelic polymorphism, but instead may reflect the specific cell type or reflect the cell's state of activation or maturation. Results from lectin chromatography and N-glycanase and neuraminidase studies suggest that the 3138 antigen is a heavily sialylated O-linked glycoprotein. The unusual features of this antigen indicate that it may be the mouse homologue of the rat W3/13 antigen and the human leukosialin/sialophorin antigens.Abbreviations used in this paper Con A concanavalin A - Gal galactose - Ga1Nac N-acetyl galactosamine - Ig immunoglobulin - IL-2 interleukin 2 - 2-ME 2-mercapto-ethanol - M _r relative mass - PAGE polyacrylamide gel electrophoresis - PMSF phenylmethylsulfonyl fluoride - SDS sodium dodecyl sulfate - Th T helper - TX-100 Triton X-100 - TTS 0.3% TX-100, 0.01 M Tris, pH 7.4, 0.15 M NaCl     

Biochemical complexity of serum HLA class I molecules

Human serum was found to contain a variety of class I-like molecules by Western blotting with anti-class I heavy chain reagents: major bands usually are observed around M _r 44 000, 40 000, and 35 000–37 000. HLA-A24-positive individuals are distinguished by higher serum levels of M _r 44 000 and 40 000 class I-like molecules than those found in HLA-A24-negative individuals. The M _r 44 000 serum molecules are probably intact class I molecules that have been shed from the cell membrane, because they contain both a transmembrane segment (TM), as deduced from detergent-binding experiments, and a cytoplasmic tail (CT), as inferred from reactivity with an antipeptide serum specific for the cytoplasmic domain of class I antigens (RaCT). The M _r 35 000 and 37 000 molecules contain neither a TM nor a CT region and therefore are probably proteolytic breakdown products of cellular and/or serum M _r 44 000 molecules, although the existence of Q10-like molecules in man cannot be ruled out. The M _r 40 000 molecules do not contain a TM region. M _r 40 000 molecules reactive with the RaCT serum were found in the minority (2/13) of sera tested. We conclude that alternative splicing resulting in a precise excision of the TM exon plays a minor role in the generation of serum HLA class I antigens.Abbreviations used in this paper B2m beta-2 microglobulin - BSA bovine serum albumin - EBV-BLCL Epstein-Barr virus-transformed B lymphoblastoid cell line - mAb monoclonal antibody - SDS-PAGE sodium dodecyl sulfate-polyacrylamide gel electrophoresis - TCA trichloroacetic acid     

Purification of GP57, and auxin-regulated extracellular glycoprotein of carrots,and its immunocytochemical localization in dermal tissues

A glycoprotein (GP57) was purified by ion-exchange and hydroxylapatite column chromatography from the 70%-ethanol precipitate of culture medium of non-embryogenic carrot cells (Daucus carota L.) grown with 2,4-dichlorophen-oxyacetic acid (2,4-D). Its apparent molecular mass (M _r) was estimated to be 57000 by sodium dodecylsulfate-polyacrylamide gel electrophoresis and 50000 by gel filtration. GP57 contained 14% (w/w) carbohydrate; the M _r of the peptide portion was estimated to be 55000 after deglycosylation by trifluoromethanesulfonic acid. GP57 is composed of two polypeptides with the same M_r and with very similar amino-acid composition but different pI values, 8.8 and 9.5. Both are rich in aspartic acid, serine and threonine, and may possess N-linked oligosaccharide chains, including fucose and xylose. A monoclonal antibody (MAb) against the purified GP57 reacted with both the pI 8.8 and the 9.5 components, as well as the deglycosylated GP57. Immunoblotting with the MAb indicated that GP57 is synthesized in and released from cultured cells which have been supplied with auxin. In immunocytochemical studies, GP57 was found in the space between the embryo and the endosperm of dry seeds, and its content decreased during germination. GP57 was also found in the endodermis and epidermis of young roots, the periderm of mature taproots, and the epidermis of petioles and young leaves.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - GP57 M _r-57000 glycoprotein - GP65 M _r-65000 glycoprotein - MAb monoclonal antibody - M _r apparent molecular mass - SDS-PAGE sodium dodecylsulfate-polyacrylamide gel electrophoresis - TFMS trifluoromethanesulfonic acid