Deglycosylation of glycoproteins by trifluoromethanesulfonic acid

Studies on the nature of the human platelet alloantigen, PlA1: localization to a 17,000-dalton polypeptide

We have examined the biochemical properties of the human platelet alloantigen system, PlA, using a preparation enriched in plasma membrane glycoproteins (GPs) IIb and IIIa as the starting material. After confirming that GPIIIa contains the PlA epitope, attempts were made to distinguish the two allelic forms of PlA (A1 and A2) using electrophoretic techniques. Whereas no difference could be discerned in the mol. wt of GPIIIa extracted from A1/A1, A1/A2 or A2/A2 platelets by one-dimensional SDS-polyacrylamide gel electrophoresis (SDS-PAGE), two-dimensional electrophoresis revealed a reproducible difference in the isoelectric point of GPIIIa derived from A2/A2 individuals. Treatment of GPIIIa with a combination of exo- and endoglycosidases resulted in apparently complete deglycosylation of the molecule, as indicated by its co-migration with chemically deglycosylated GPIIIa in SDS-PAGE. The enzymatically deglycosylated protein retained its full ability to react with anti-PlA1 antibodies. Tryptic digestion of GPIIIa resulted in the generation of a number of smaller polypeptides, including one of 17,000 daltons, that contained the PlA1 determinant. These results suggest that the carbohydrate moieties of GPIIIa are unimportant to the expression of the PlA system, and that the charge difference between the two allelic forms of GPIIIa may reflect a subtle amino acid difference(s) within a 17K polypeptide region of the GP.

Cytochrome b-245 from human neutrophils is a glycoprotein

Cytochrome b-245 is a glycoprotein. It runs as a broad band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and its apparent Mr varies with the concentration of acrylamide. It stained positively with Schiff reagent and with silver stains after oxidation with periodic acid. It preferentially bound the lectin of Phaseolus vulgaris (type III), and cleavage of carbohydrate with endoglycosidase F resulted in a sharp band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis with an apparent Mr of 55000 G.l.c. analysis of carbohydrate showed this to account for about 15% of the Mr and N-acetylglucosamine and galactose to be the major sugars.

Immunological analysis of chick notochord and cartilage matrix development with antisera to cartilage matrix macromolecules

Transverse frozen sections from the postcephalic region of stage 9-16 chick embryos and from the wing bud region of stage 17-31 embryos were stained with antibodies to the major extracellular matrix components of cartilage. These probes included unfractionated A1 and A2 antisera to the major cartilage proteoglycan, affinity-purified purified antibodies to the proteoglycan core protein and to Type II collagen, and a monoclonal antibody to keratan sulfate. In embryos as early as stage 10, notochord stained specifically with the keratan sulfate monoclonal antibody. At this stage the notochord, as well as surrounding tissues, were negative to cartilage proteoglycan and collagen antibodies. Positive staining with the latter probes was coordinately acquired by notochord cells and their accompanying sheath around stage 15, while surrounding tissues remained negative. At this stage, the ventral region of the perispinal cord sheath exhibited light staining with the proteoglycan and keratan sulfate antibodies though failing to react to Type II collagen antibodies. Positive staining of notochord and ventral spinal cord persisted through later developmental stages. As revealed by immunofluorescence, definitive vertebral chondroblasts first emerged at approximately stage 23 and definitive limb chondroblasts at stage 25. The results are discussed in terms of the possible multiple roles of notochord in early embryogenesis.

O-linked oligosaccharides of mouse egg ZP3 account for its sperm receptor activity

Previously, we reported that ZP3, one of three different glycoproteins present in the mouse egg's zona pellucida, serves as a sperm receptor. Furthermore, small glycopeptides derived from egg ZP3 retain full sperm receptor activity, suggesting a role for carbohydrate, rather than polypeptide chain in receptor function. Here, we report that removal of O-linked oligosaccharides from ZP3 destroys its sperm receptor activity, whereas removal of N-linked oligosaccharides has no effect. A specific size class of O-linked oligosaccharides, recovered following mild alkaline hydrolysis and reduction of ZP3, is shown to possess sperm receptor activity and to bind to sperm. The results presented strongly suggest that mouse sperm bind to eggs via O-linked oligosaccharides present on ZP3.

Presynaptic neurones may contribute a unique glycoprotein to the extracellular matrix at the synapse

As the extracellular matrix at the original site of a neuromuscular junction seems to play a major part in the specificity of synaptic regeneration, considerable attention has been paid to unique molecules localized to this region. Here we describe an extracellular matrix glycoprotein of the elasmobranch electric organ that is localized near the nerve endings. By immunological criteria, it is synthesized in the cell bodies, transported down the axons and is related to a glycoprotein in the synaptic vesicles of the neurones that innervate the electric organ. It is apparently specific for these neurones, as it cannot be detected elsewhere in the nervous system of the fish. Therefore, neurones seem to contribute unique extracellular matrix glycoproteins to the synaptic region. Synaptic vesicles could be involved in transporting these glycoproteins to or from the nerve terminal surface.

The synthesis and in vivo assembly of functional antibodies in yeast

The yeast Saccharomyces cerevisiae can synthesize, process and secrete higher eukaryotic proteins. We have investigated the expression of immunoglobulin chains in yeast and demonstrate here the synthesis, processing and secretion of light and heavy chains, the glycosylation of heavy chain, the intracellular localization of these foreign proteins by immunofluorescence, and the detection of functional antibodies in cells co-expressing both chains. This may provide the basis of a microbial fermentation process for the production of monoclonal antibodies. The co-expression of light and heavy chains in Escherichia coli has been reported but functional antibodies were not assembled in vivo. Furthermore, only low-level assembly of these chains was found in vitro.

Purification and partial characterization of a megakaryocyte colony-stimulating factor from human plasma

Human plasma obtained from patients with hypomegakaryocytic thrombocytopenia contains a factor that promotes megakaryocyte colony formation by normal human marrow cells. This megakaryocyte colony-stimulating factor was purified from such a plasma specimen. A four-step purification scheme which included ammonium sulfate precipitation, diethylaminoethyl-Sepharose chromatography, affinity chromatography on wheat germ lectin-Sepharose 6MB, and reverse-phase high performance liquid chromatography resulted in a recovery of 16.6% of the initial biological activity and an increase in specific activity by 3,489-fold. The purified protein produced a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Purified megakaryocyte colony-stimulating factor was capable of promoting megakaryocyte colony formation at a concentration of 7.6 X 10(-8) M. Megakaryocyte colony-stimulating factor was shown to be a glycoprotein and had an apparent 46,000 mol wt. Deglycosylation of megakaryocyte colony-stimulating factor by treatment with trifluoromethane-sulfonate resulted in the loss of its ability to promote megakaryocyte colony formation. Megakaryocyte colony-stimulating factor appears to be an important regulator of in vitro human megakaryocytopoiesis at the level of the colony-forming unit megakaryocyte and may be of importance physiologically.

Generation and characterization of mouse monoclonal antibodies to the myelin-associated glycoprotein (MAG)

A panel of mouse monoclonal antibodies to rat and human myelin-associated glycoprotein (MAG) was developed. Normal mice were unresponsive to rat MAG, and successful immunization with rat MAG was only achieved in autoimmune NZB mice. By contrast, all strains of mice were responsive to human MAG. The monoclonal antibodies developed differ with respect to immunoglobulin type, their specificity for human and/or rat MAG, and their recognition of protein or carbohydrate epitopes in MAG. In general, the antibodies that react with the protein backbone recognize both rat and human MAG, whereas a large number of the monoclonal antibodies recognize a carbohydrate determinant in human MAG that is not in rat MAG. Immunocytochemical staining of adult human spinal cord with the monoclonal antibodies resulted in periaxonal staining of myelin sheaths similar to that produced by well-defined, rabbit, polyclonal anti-MAG serum. In addition, the antibodies recognizing carbohydrate determinants in human MAG strongly stained oligodendrocyte cytoplasm. These monoclonal antibodies will be of value for the further chemical and biological characterization of MAG.

Deglycosylation of chondroitin sulfate proteoglycan by hydrogen fluoride in pyridine

The original deglycosylation procedure using HF/pyridine has been modified for maximal removal of carbohydrate from chondroitin sulfate proteoglycan, with minimal alteration of the core protein. Gas-liquid chromatography analysis after treatment for various times showed that 95% of xylose and mannose and 70-85% of other sugars were removed within 30 min, indicating that almost all chondroitin sulfate chains and about 80% of N- and O-linked oligosaccharides were removed. In contrast to the loss of carbohydrate, no change in amino acid composition or loss of immunoreactivity occurred. Longer treatment of up to 16 h resulted in little additional removal of carbohydrate, but did cause a significant decrease in solubility and recovery of the deglycosylated product. Optimal removal of xylose residues after about 1 h was also shown by maximal acceptor activity of the product in a xylosyltransferase assay. Rapid removal of the HF reagent by vacuum evacuation and ion-exchange chromatography, coupled with the reduced time of treatment allowed recovery of an intact, homogenous protein core that is amenable to structural and sequence studies.

T helper cell recognition of idiotopes on lambda 2 light chains of M315 and T952: evidence for dependence on somatic mutations in the third hypervariable region

Previous work has indicated that BALB/c T helper cells (Th) recognize an idiotope expressed on a 88-114/117 fragment of V lambda 2 of BALB/c myeloma protein 315. In the present study the antigenic structure of this idiotope was further analyzed. Conventional carrier-specific Th elicited by immunization of BALB/c mice with free lambda 2(315) did not cross-react with the free lambda 2 chain of the BALB/c myeloma protein T952 which differs from lambda 2(315) in five amino acid positions (38, 94, 95, 96, 99). Similarly, Th primed with free lambda 2T952 did not respond to a boost with free lambda 2(315). Thus, BALB/c lambda 2(315)-specific Th recognize an idiotope that depends on some or all of the residues at positions 94, 95, 96 and 99. Furthermore, free lambda 2T952 contains an idiotope immunogenic to Th that depends on some or all of residues 38, 94, 95, 96 and 99. Th recognition of the free lambda 2T952 idiotope was quenched upon H + L chain assembly because Th elicited by free lambda 2T952 did not respond to a boost with the complete T952 myeloma protein. In contrast to the lack of Th cell cross-reactivity, some of the antisera from BALB/c mice immunized with free lambda 2T952 cross-reacted with free lambda 2(315), free lambda lJ558 and free lambda 3CBPC49 but not with free kappa W3129 or polyclonal L chains. The H chain of T952 (alpha, kappa 2) myeloma protein was abnormally short (Mr = 48 000) and T952 existed as a halfmere probably due to this H chain deletion. Furthermore, H and L chains were disulfide bonded to each other.

Monoclonal antibodies to proteokeratan sulfate of rabbit corneal stroma

Hybridomas were developed that secreted monoclonal antibodies against two proteokeratan sulfates (PKS) from rabbit corneal stroma. A total of 28 antibodies were isolated, all of the IgG type with kappa light chains. All were found to react with both PKSs. As judged by immunohistochemical staining, none of them reacted with scleral or conjunctival components, nor with sections of skin, but all reacted with nasal cartilage. When tested by enzyme-linked immunosorbent assays, against components of the proteoglycans, all of the antibodies reacted with keratan sulfate-peptide (isolated from papain digests of PKS or of cartilage proteoglycan), and all but two reacted with oligosaccharide-containing protein cores (prepared by keratanase treatment of PKS). Reactivity with cores was probably due to residual portions of the keratan sulfate chains since the endogenous oligosaccharide-peptides (non-sulfated, non-keratan sulfate oligosaccharides isolated after papain digestion of PKS) were not active. None of the antibodies reacted with protein cores made by removal of carbohydrate by hydrolysis with trifluoromethanesulfonic acid. All except one reacted with fragments of keratan sulfate (made by keratanase digestion). These observations are evidence for structural requirements at three different levels of completeness of the antigen for recognition among the various antibodies. In addition, none of the antibodies reacted immunohistochemically with macular dystrophic corneas, confirming the finding of others that the defect lies in the keratan sulfate portion of the proteoglycans.

Nerve growth factor biosynthesis: isolation and characterization of a guinea pig prostate kallikrein

Guinea pig prostate contains one major soluble esteropeptidase activity. The protein has been purified and characterized and found to be a glycoprotein comprised of a single polypeptide chain. The molecular has a similar Km for lysine and arginine synthetic substrates, although the Vmax for arginine is much greater than that for lysine. Amino-terminal sequence analysis has also revealed a marked degree of homology to mouse gamma-nerve growth factor (NGF) and the kallikrein family of serine proteases. In contrast to gamma-NGF, however, the guinea pig enzyme does not appear to form stable complexes with beta-NGF.

The role of the carbohydrate moiety on the size heterogeneity and immunologic determinants of human testosterone-estradiol-binding globulin

Human testosterone-estradiol-binding globulin (hTeBG) has been purified to apparent homogeneity by several laboratories using procedures which, in most instances, were labor intensive. In this report, hTeBG was purified from pregnancy serum by a newly developed two step procedure involving sequential affinity chromatography and ion-exchange high performance liquid chromatography (ion-exchange HPLC). The purity of the final product was confirmed by silver stained SDS-polyacrylamide gel and reverse phase HPLC monitored at 206 nm. hTeBG purified by ion-exchange-HPLC maintained binding activity by Dextran coated charcoal (DCC) assay and size heterogeneity on SDS-polyacrylamide gels which were indistinguishable from those of the proteins purified by conventional chromatography. Removal of the carbohydrate moiety from the molecule by both enzymatic and chemical treatment reduced the apparent molecular size and eliminated lectin binding of hTeBG subunits. Deglycosylation did not, however, abolish or alter the distribution of the protomeric forms of this subunit. We conclude that hTeBG is a dimer whose monomer exhibits two protomeric forms which is not a result of carbohydrate heterogeneity. In addition, disialylated and deglycosylated hTeBG exhibited antigenic determinants identical to the native protein.

Molecular weight heterogeneity of bovine serum transferrin

Cattle transferrin (Tf) was purified from serum of variant A and four bands were isolated. The peptide patterns of these bands when cleaved by proteases and by cyanogen bromide (BrCN) were compared, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Variant A displays two groups of molecules--large (L) and small (S)--on SDS-PAGE; the molecular weight of the L bands is 78,400 +/- 1700 and that of the S bands is 72,000 +/- 1700. However, S-band molecules could not be produced artificially by heat treatment of L bands in the presence of SDS and 2-mercaptoethanol. Since deglycosylated Tf also showed molecular weight heterogeneity, the sugar moieties of Tf other than sialic acids were not the cause of the heterogeneity. These results suggest that heterogeneity within a given variant is due to the presence of two kinds of molecule of different molecular weight. The peptide patterns of L and S bands produced by proteases and those produced by BrCN were distinctly different from each other. However, the stepwise degradation patterns of L and S bands resembled each other when treated with both chymotrypsin and BrCN. This suggests that L-band molecules differ from S-band molecules only in the presence of an additional carboxyl-terminal peptide.

Identification of glycosphingolipid-glycoprotein hybrids in gastric epithelium

A glycolipid fraction, obtained from dog gastric epithelium by detergent solubilization, was found to contain the glycoconjugates with features common to both glycosphingolipids and glycoproteins. Three such compounds have been purified to homogeneity and their composition and structural characteristics determined. The purified glycosphingolipid-glycoprotein hybrids had a molecular weight in the range of 14,000 and contained 88.2 - 91.1% carbohydrate, 3.1 - 4.5% protein, 2.0 - 2.4% sphingosine, and 1.1 - 1.9% fatty acids. The oxidation of the olefinic bond of sphingosine followed by beta-elimination reaction led to the release from each compound of glucose and mannose containing oligosaccharides. Deglycosylation with trifluoromethanesulfonic acid exposed the core regions of the hybrid molecules which were found to consist of sphingosine, glucose, N-acetylglucosamine and amino acids. The data suggest that glycosphingolipid-glycoprotein hybrid molecules are held together by amide linkages between the sphingosine and aspartic or glutamic acid.

Human monoclonal antibodies to myelin-associated glycoprotein are directed against the polypeptide and not the carbohydrate moiety

We have used an approach which combines the technique of electrophoretic blotting of polyacrylamide gels with methods for the degradation of carbohydrates, to study the myelin-associated glycoprotein (MAG)-specific antibodies found in 5 patients with demyelinating neuropathy. Our results show that it is possible to deglycosylate proteins on nitrocellulose blots and then to examine their antigenicity and lectin-binding properties. With MAG, our findings suggest that the monoclonal IgM antibodies from all the patients studied have specificity for the polypeptide and not the carbohydrate moiety.

Studies on the subunits of human myeloperoxidase

The subunit composition of human myeloperoxidase was studied with the use of sodium dodecyl sulphate/polyacrylamide-gel electrophoresis and gel filtration. The subunit pattern observed depended on the manner in which the enzyme was treated before analysis. Reduction before heat treatment in detergent led to two main protein species (Mr 57 000 and 10 500), whereas reduction during or after heat treatment yielded an additional species of Mr 39 000. Heating without any reductive pretreatment yielded the 39 000-Mr form as the major electrophoretic species. Carbohydrate staining showed large amounts of sugar on the 57 000-Mr species and little on the 10 500-Mr form. Significant amounts of haem were associated with this latter subunit. Haem also seemed to be associated with the 57 000-Mr form but not with the 39 000-Mr one. These three subunit forms were isolated and their amino acid composition analysed. The 57 000-Mr and 39 000-Mr forms had very similar amino acid composition and yielded an apparently identical collection of fragments on incubation with CNBr. Once separated, the subunits could not be interconverted. Generally, minor amounts of other molecular-mass forms were observed. The nature of the various molecular-mass forms originating from myeloperoxidase is discussed.

Structure and interactions of heparan sulfate proteoglycans from a mouse tumor basement membrane

Various forms of heparan sulfate proteoglycan were solubilized from the mouse Engelbreth-Holm-Swarm (EHS) sarcoma by extraction with 0.5 M NaCl, collagenase digestion and extraction with 4 M guanidine. They could be separated into high (greater than or equal to 1.65 g/ml) and low (1.38 g/ml) buoyant density variants. The high-density form from the NaCl extract and collagenase digest had Mr = 130000 and So20,W = 4.5 S and contained 4-10% protein, indicating Mr = 5 000-12 000 for the protein core. This proteoglycan exhibited polydispersity as shown by rotary shadowing electron microscopy and ultracentrifugation. An average molecule consisted of four heparan sulfate chains (Mr = 29 000) each with a length of 32 +/- 10 nm. The low-density form (Mr about 400 000) could not be completely purified and contained about 50% protein. As shown by radioimmunoassay, the various proteoglycans shared similar protein cores. Labeling of the tumor in vivo or in vitro demonstrated preferential incorporation of radioactive sulfate in the high-density form. The high-density proteoglycan interacted in affinity chromatography by virtue of its heparan sulfate chains with laminin, fibronectin, the globular domain NC1 and the triple helix of collagen IV. These interactions were abolished at moderate concentrations of NaCl (0.1-0.2 M) and in the presence of heparin, chondroitin sulfate or dextran sulfate. Interactions with the globule NC1 could also be demonstrated by velocity band centrifugation in sucrose gradients and a binding constant of about 10(6) M-1 was derived.

High-performance liquid chromatographic separation of glycopeptides from Nereis cuticle collagen

To facilitate the structural studies of invertebrate collagens, a sensitive and effective method was developed, using reverse-phase high-performance liquid chromatography for preparative isolation of the collagen subunits and their clostridial collagenase-derived peptides; the methods have been applied to Nereis cuticle collagen. The two subunits of denatured Nereis cuticle collagen, termed A and B, were initially separated by high-performance liquid chromatography. These polypeptides, with Mr of about 0.5 million, were each exhaustively digested with clostridial collagenase. The digest of the A subunit, which contains all of the uronic acid, was enriched for the uronic acid-containing glycopeptides by means of gel filtration. These glycopeptides were resolved into 23 major peaks, using reverse-phase HPLC, over a 5-h elution time, with an acetonitrile gradient (0-20%) containing 0.1% TFA. The amino acid composition data suggests that the peptides are of variable length, from 5 to 17 residues, while beta-elimination studies show that the uronic acid-containing moieties are all O-glycosidically linked to threonine residues, in the peptides examined. The amino acid sequence of one of the major glycopeptides was determined and found to be Gly-Hyp-Ala-Gly-Gly-Ile-Gly-Glu-Thr-Gly-Ala-Val-Gly-Leu-Hyp. The amino acid compositions of glycosylated and nonglycosylated peptides which had eluted, numbering about 100, showed a correspondence between hydrophobicity or hydrophilicity and emergence time from the column. We also found that the peptides most enriched in 4-hydroxyproline emerged earliest. These studies provide a foundation for elucidating the detailed structures of the large, unusual subunits of a well-characterized cuticle collagen.

Deglycosylation by trifluoromethanesulphonic acid of endopeptidase-24.11 purified from pig kidney and intestine

Endopeptidase-24.11, an integral microvillar membrane enzyme, exists in differently glycosylated forms when purified from pig kidney and intestine [Fulcher, Chaplin & Kenny (1983) Biochem. J. 215, 317-323]. When these glycoproteins, and another form of the kidney enzyme prepared from the Yucatan dwarf strain of piglet, were treated, under controlled conditions, with trifluoromethanesulphonic acid, the proteins were freed of carbohydrate and all had the same apparent subunit Mr (77 000) even though the untreated forms varied from Mr 89 000 to Mr 95 000.

Molecular characteristics of the epitope in myelin-associated glycoprotein that is recognized by a monoclonal IgM in human neuropathy patients

The antigen for the IgM monoclonal antibody from patients with IgM paraproteinemia and peripheral neuropathy is the myelin-associated glycoprotein (MAG), a minor protein component of both human PNS myelin and human CNS myelin. Sera from five patients were found to react with identical proteolytically derived fragments of MAG indicating that the monoclonal IgM from these patients is recognizing a common epitope. Furthermore, the lectin concanavalin A reacts with these fragments and deglycosylation of isolated MAG abolishes the recognition of MAG by the patient monoclonal IgM. Therefore, it appears that the monoclonal IgM from these five patients recognizes a common epitope which contains carbohydrate moieties. These data are consistent with the idea that the peripheral myelin sheath is involved in an autoimmune response directed against MAG.

Deglycosylated ovine lutropin: preparation and characterization by in vitro binding and steroidogenesis

Ovine lutropin (oLH) subunits were deglycosylated in anhydrous hydrofluoric acid. All possible combinations of native and deglycosylated alpha- and beta-subunits were prepared and characterized. The two native plus deglycosylated counterpart preparations showed properties intermediate between the native only and the deglycosylated subunit hybrid. For brevity, only the properties of the latter hybrid were described in detail. Deglycosylation did not alter subunit-subunit recombination, protein conformation (circular dichroism) or the peptide chains (N-termini). Deglycosylation enhanced receptor-binding activity, but the carbohydrate moieties are important for maximal steroidogenesis (Leydig cell testosterone production). The deglycosylated hybrid molecule acts as an antagonist or agonist to native hormone action depending on the test system and conditions. The deglycosylated hormone binds to the receptor much more rapidly than the native hormone and binding plateaued at a higher level in the case of the deglycosylated hormone, although cross-labeling of tracers (either native or deglycosylated) indicated that competition was for the same type of receptors. To eliminate internalization of the hormone as a factor in the binding studies we used broken cell (membrane) preparations of Leydig cells. Differences in the preparations are thus attributable to a greater 'on-rate' for the deglycosylated hormone. The 'off-rate' from the receptor was essentially equal for both native and deglycosylated hormones. For this reason the deglycosylated hormone has only limited antagonistic action for native hormone activity.

A 45-kDa human T-cell membrane glycoprotein functions in the regulation of cell proliferative responses

A 45-kDa human T cell surface glycoprotein which is tightly bound in the membrane of the resting T cell is released into the cell medium in soluble form after cell growth activation by phytohemagglutinin or neuraminidase/galactose oxidase treatments. In limited proteolysis by Staphylococcus aureus V8 protease, two major 35-kDa and 27-kDa peptide fragments of the surface-iodinated 45-kDa protein are common to the membrane-bound and the released forms, but a third 18-kDa fragment is observed exclusively with the released protein. The apparent molecular masses of the deglycosylated peptide backbones of the membrane-bound and the released molecule are 30 +/- 1 kDa, although a small size difference cannot be excluded. A polyclonal rabbit anti-(T cell membrane protein) antiserum precipitates the 45-kDa protein. A monoclonal anti-(45-kDa protein) antibody precipitates the membrane-bound 45-kDa protein solubilized with octyl glucoside, but does not precipitate the released protein. In cell culture assays, the monoclonal anti-(45-kDa protein) antibody specifically enhances the cell proliferative responses in phytohemagglutinin-treated and mixed lymphocyte cultures. These observations suggest that the 45-kDa protein has a specific receptor function in the regulation of cell proliferative responses.

A comparison of tomato (Lycopersicon esculentum) lectin with its deglycosylated derivative

A deglycosylated derivative of tomato (Lycopersicon esculentum) lectin was prepared with the use of trifluoromethanesulphonic acid. Its properties were generally similar to those of the native lectin, but differences were evident in terms of relative agglutinating activity towards sheep, (untreated) human and trypsin-treated human erythrocytes. The two forms of tomato lectin were used in conjunction with a battery of specific antisera to investigate structural relatedness among solanaceous lectins. Immunological cross-reactivity between tomato, potato and Datura lectins depends on the integrity of the glycosylated region of those lectins; that between Datura lectin and other seed lectins, however, has a separate structural basis.

Monoclonal antibodies to the major structural glycoprotein of the Chlamydomonas cell wall

A family of monoclonal antibodies (McAb) has been raised to the major cell-wall structural glycoprotein of the green alga Chlamydomonas reinhardii. The work represents an approach using McAb to the structure and function of plant cell wall-components. On the basis of cross-competition assays, the McAb have been subdivided into six groups. Various lines of evidence indicate that some of these group's e.g. group III, contain McAb which recognise specific oligosaccharide side chains of the glycoprotein. Heterogeneity of the oligosaccharide side chains is demonstrated, by probing 'Western' blots of separated glycoproteins and glycopeptides with the McAb. The results are discussed in relation to the possibility of raising McAb as probes for the structure and function of higher-plant cell-wall oligosaccharides, which are increasingly being shown to be important in cell-cell recognition phenomena and host-pathogen interactions.

Immunochemical characterization of the androgen-dependent spermine-binding protein of the rat ventral prostate

A solid-phase radioimmunoassay was developed to measure the level of the androgen-dependent spermine-binding protein (SBP) in the cytosol fraction of the rat ventral prostate during endocrine manipulation. The concentration of SBP and immunologically cross-reacting material (CRM) in the ventral prostate was at least 5000 times higher than the level of CRM detected in rat serum or cytosol from other rat tissues. Cytosol from the ventral prostate of intact rats was separated by DEAE-cellulose chromatography into three major fractions of CRM. One of these fractions corresponded to the elution position of SBP. Cytosol prepared from rats 48 h after castration lacked SBP and one of the two other fractions of CRM. This loss coincided with an increase in CRM in the remaining fraction. No significant difference was detected in the total level of CRM when intact and 48 h-castrated rats were compared. Injection of rats with 5 alpha-dihydrotestosterone (DHT) immediately after castration prevented these changes in the profile of CRM. Several proteins cross-reacting with antibodies to purified SBP were detected in cytosol by using an immunoblot procedure. The highest-Mr band corresponded to SBP. The effect of short- and long-term castration and subsequent DHT treatment on CRM was studied by using the immunoblot technique. Short-term castration (2 days) led to the disappearance of CRM coinciding with SBP (Mr 35 000-38 000) and an increase in smaller forms of CRM (Mr 24 000 and 22 000). Injection of rats with DHT 2 days after castration led to the reappearance of CRM corresponding to SBP, which returned to normal levels within 4 to 5 days of treatment. Long-term castration (up to 14 days) led to a gradual disappearance of all CRM; subsequent DHT treatment led to the reappearance of all forms of CRM and normal levels were attained within 5 days. We have identified SBP and the various forms of CRM as a secretory product of the rat ventral prostate by immunohistochemical staining and by DEAE-cellulose fractionation of prostatic fluid. Prostatic fluid is rich in proteolytic activity and these proteinases may be responsible for processing SBP to small forms of CRM.

IgM in a human neuropathy related to paraproteinemia binds to a carbohydrate determinant in the myelin-associated glycoprotein and to a ganglioside

The IgM in three patients with paraproteinemia and peripheral neuropathy was shown to bind to human myelin-associated glycoprotein (MAG) that had been purified to homogeneity by gel filtration on Sepharose CL-6B. The antigenic determinant reacting with the IgM from all three patients was in the carbohydrate part of the MAG molecule. In addition, the IgM from the same three patients bound to a single ganglioside of human sciatic nerve. The results indicate that the IgM paraproteins in these patients react with a carbohydrate determinant that is shared between MAG and a peripheral nerve ganglioside.

Highly phosphorylated region of chicken riboflavin-binding protein: chemical characterization and 31P NMR studies

Phosphate residues on chicken riboflavin-binding protein (RBP) have been implicated in the recognition and deposition of the protein-vitamin complex in egg yolk by the ovary. We demonstrate that all of the phosphate of RBP is linked to serine and that most if not all of the phosphoserine residues are contained in a single tryptic peptide having a composition SerP8, Glx6, His2, Leu2, Ala, Met, Lys. Despite differences in the tissue of synthesis, RBPs isolated from egg yolk and egg white yield phosphopeptides virtually identical in their amino acid composition and 101-MHz 31P NMR spectra. This implies that posttranslational phosphorylation of RBP is the same in liver and oviduct. The 31P NMR spectrum of the phosphopeptide is quite different from that of the phosphoprotein. The 31P NMR spectra of egg yolk and egg white RBP are quite similar but not identical and are unaffected by the binding of riboflavin. Optimal resolution of seven phosphorus resonances was obtained near pH 7.0. The titration behavior of all the phosphoserine residues is similar. We propose that this highly anionic peptide, exposed at the surface of RBP, is the principal determinant for the uptake of RBP by the vitelline membrane of the ovarian follicle.

A novel procedure for labeling immunoglobulins by conjugation to oligosaccharide moieties

A novel method is described for the biotinylation of immunoglobulins. The procedure relies on the generation of reactive aldehydes on the carbohydrate moieties of the immunoglobulin by oxidation with sodium periodate and subsequent reaction with biotin hydrazide. The method is simple and specific and results in stable conjugates retaining full immunologic activity. It has been applied successfully to a number of mouse monoclonal antibodies of both IgG and IgM classes, and to human IgM preparations. The procedure may also be applied to conjugation of immunoglobulins with fluorescent dyes.

Structure and function of the Ca antigen

The Ca antigen, which can be detected in a wide range of malignant human tumours by means of the Cal antibody, is a glycoprotein of the mucin type. At least 95% of the carbohydrate is 0-glycosidically linked to the polypeptide which contains high proportions of glycine, serine and glutamic acid. The carbohydrate has a very simple structure: it is composed almost entirely of tetra- tri- and disaccharides having the general formula (NeuNac)n leads to [Gal leads to GalNac] alpha leads to, where n = 0, 1 or 2. In many malignant cell lines, the antigen is produced constitutively in vitro; but in one that has been examined, its synthesis can be induced by high concentrations of lactate. Evidence is presented for the view that a primary function of this glycoprotein is to shield the cells that produce it from hydrogen ion concentrations outside of the physiological range. The presence of the Ca antigen in malignant tumours may thus be a reflection of metabolic conditions that are known to be characteristics of such tumours.

The T3 complex on human thymus-derived lymphocytes contains two different subunits of 20 kDa

The human cell surface antigen T3 is involved in several T lymphocyte specific functions, as determined by the effect of monoclonal antibodies (OKT3, anti-Leu-4, UCHT1) directed at this molecular structure. The main target antigen of these monoclonal antibodies is a glycoprotein of 20 kDa. It is associated with four, less predominant, structurally distinct glycoproteins of 25-28 kDa, 37 kDa and 44 kDa. Of these molecules only the 20-kDa T3 antigen could be labeled with the hydrophobic reagent 5-iodonaphthyl-1-azide (INA). Here we present evidence that the main 20-kDa T3 antigen is comprised of, in fact, two structurally different molecules. One of these is a glycoprotein with a protein backbone of 14 kDa, the other is an unglycosylated protein of 20 kDa. This unglycosylated protein is labeled specifically with INA. Additional evidence for the existence of two different 20-kDa T3 antigens is provided by studies using the enzymes endo-beta-N-acetylglucosaminidase H and endo-beta-N-acetylglucosaminidase F and the drug tunicamycin. We hypothesize that the specific susceptibility to labeling with INA of the unglycosylated 20-kDa T3 form reflects a positioning in the lipid bilayer different from that of the glycosylated 20-kDa T3 form.

The properties of potato (Solanum tuberosum) lectin after deglycosylation by trifluoromethanesulphonic acid

Potato (Solanum tuberosum) lectin, which is a very highly glycosylated glycoprotein, has been completely deglycosylated by use of the trifluoromethanesulphonic acid reagent described by Edge, Faltnek, Hof, Reichert & Weber [(1981) Analyt. Biochem. 118, 131-137]. This shows that both hydroxyproline-arabinofuranoside and serine-galactopyranoside linkages are hydrolysed. The deglycosylated lectin is still functional and cross-reacts with one component of an anti-(potato lectin) antiserum.

Application of denatured, electrophoretically separated, and immobilized lysates of herpes simplex virus-infected cells for detection of monoclonal antibodies and for studies of the properties of viral proteins

We report the use of herpes simplex virus type 1 (HSV-1)- and HSV-2-infected cell polypeptides (ICPs) separated by electrophoresis in polyacrylamide gels and transferred to nitrocellulose to (i) detect monoclonal antibodies to viral polypeptides and to (ii) study the properties of the proteins with the monoclonal antibodies. Our results were as follows. (i) When the antigens were electrophoretically separated in denaturing gels and then immobilized on nitrocellulose strips, we detected a greater diversity of monoclonal antibodies to viral proteins than when we used the technique of immune precipitation of soluble, nondenatured viral antigens. The primary advantage of the technique is in the detection of nonprecipitating antibody and of antibody to poorly soluble antigens not available for reaction in preparations cleared by high-speed centrifugation before immune reaction. (ii) Studies of the viral polypeptides reactive with three monoclonal antibodies indicated that the technique can be used to investigate several properties of the antigens. Specifically, monoclonal antibody to ICP 4 confirmed the accumulation of viral protein in the nucleus and the mapping of the gene in the S component. The results showed, however, that HSV-1 and HSV-2 ICP 4 do have common antigenic determinants. The reaction of a nonprecipitating monoclonal antibody with electrophoretically separated, immobilized polypeptides contained in cytoplasmic and nuclear fractions, those chemically deglycosylated, or those specified by specific HSV-1 x HSV-2 intertypic recombinants identified the antigens reactive with the second monoclonal antibody as various forms of glycoprotein gC. Of particular interest was a set of four antigens, 39,000 to 46,500 in apparent molecular weight, reactive with each of several monoclonal antibodies. These studies showed that two polypeptides partition in the cytoplasm and two in the nucleus and that all comap with the previously mapped ICPs 35 and 37 in the region of the genome defined by the viral thymidine kinase gene on the left and the glycoprotein gA/B gene on the right. Unlike ICP 4 and gC, the four polypeptides are linked by intermolecular bisulfide bonds, inasmuch as the polypeptides were not at the expected locations upon denaturation and electrophoresis in the absence of reducing agents.

Identification and partial characterization of the secreted form of the fourth component of human complement: evidence that it is different from major plasma form

Immunoprecipitation of human C4 from plasma followed by NaDodSO4/polyacrylamide gel electrophoresis under reducing conditions revealed the expected alpha, beta, and gamma chains as well as a smaller quantity of a molecule containing an alpha chain (p98) approximately equal to 5,000 daltons heavier than the normal alpha chain. Further studies on p98 indicated that it covalently incorporated methyl-amine, was present at a concentration of approximately equal to 8% of the principal plasma form of the C4 alpha chain, and was found in highly purified C4 preparations. Hep G2, a human hepatoma-derived cell line, was found to secrete a C4 molecule in which the alpha chain had a molecular weight identical to that of the p98 protein found in plasma. The secreted C4 molecule possessed hemolytic activity. The 5,000-dalton difference in the alpha chain was localized to the COOH terminus and was attributed to an additional polypeptide. We propose that p98 is the alpha chain of the secreted form of C4, which is processed extracellularly by proteolytic cleavage to the principal C4 molecule found in plasma.

Biochemical comparison of the T6 antigen and HLA-A,B antigens

The human thymic differentiation antigen T6, which was found to be associated with beta 2-microglobulin, was compared to the HLA-A,B antigens. Using a heteroantiserum prepared against denatured heavy chains of HLA-A,B antigens, no cross-reactivity with denatured T6 could be detected. The molecular weight of the protein backbone of T6 was found to be 34,000 as compared to 40,000 for the HLA-A,B antigens. Also, not only was the percentage of carbohydrate of T6 (25-35%) different from the HLA-A,B antigens (10%), but lectin binding studies showed that their sugar composition may differ. The two forms of T6, which previously had been found on MOLT-4 cells, appeared to have different levels of glycosylation, but apparently had the same protein backbone. T6, like HLA, has a hydrophobic domain, since it could be labeled with [125I]iodonaphthylazide. We conclude from these studies that T6 may be a class I MHC antigen which is different from the classical HLA-A,B antigens.

A microapparatus for liquid hydrogen fluoride solvolysis: sugar and amino sugar composition of Erysiphe graminis and Triticum aestivum cell walls

The assembly and use of a simple and safe apparatus for HF solvolysis of microgram amounts of cell walls, polysaccharides, or glycoproteins are described. Using this apparatus the cell wall composition of Erysiphe graminis was compared with that of its wheat host. The HF solvolysis combined with TFA posthydrolysis considerably increased sugar yields compared with TFA hydrolysis alone, due mainly to increased yields of glucose from wheat, and glucosamine from Erysiphe, corresponding to cellulose and chitin, respectively. A potentially useful method for determining amounts of fungal hyphae in plant tissue is also provided.

Characterization of the Mr difference between secreted murine fourth component of complement and the major plasma form: evidence for carboxyl-terminal cleavage of the alpha chain

The alpha-chain of murine fourth component of complement (C4) secreted by cells in vitro and in vivo has a Mr that is larger by approximately equal to 4,000 than that of the alpha-chain of the principal form of C4 in plasma. By using in vivo labeling of C4 with [35S]methionine, C4 was shown to be first synthesized with the higher Mr ("secreted") alpha-chain, which was then quickly processed (t1/2 approximately equal to 1 hr) extracellularly to the mature ("plasma") C4 possessing the lower Mr alpha-chain. Both forms of C4 were functional as assayed by the ability of their alpha-chains to be cleaved by the protease C1, to bind methylamine, and to undergo denaturation-dependent autolysis. When secreted C4 and plasma C4 were activated to C4b, the Mr difference of 4,000 was maintained in the alpha'-chains. The Mr difference was localized to the carboxyl-terminal autolytic fragment of the alpha-chain and was unaffected by the removal of carbohydrate. C4 from resident peritoneal macrophage cultures could be converted to the plasma form by incubation with heparin/plasma. This conversion could be blocked by EDTA or 1,10-phenanthroline. These data suggest that an enzyme, presumably a neutral proteinase present in mouse plasma, cleaves the carboxyl terminus of newly synthesized C4 alpha-chains, thereby creating the major form of C4 in plasma.