Partial deglycosylation of blood-group-specific glycoproteins.

The time course for the partial deglycosylation of blood-group-specific glycoproteins from human ovarian-cyst fluids with 0.25 M-H2SO4/acetic acid and 6 M-HCl in methanol was studied. Either reagent readily removed about 80% of the carbohydrate from the glycoproteins to leave non-diffusible glycopeptides that contain N-acetylgalactosamine as the predominant sugar. Some changes in amino acid distribution were observed during the deglycosylation, which were attributed to an accelerated break-up of the nonglycosylated regions of the parent glycoprotein. The N-acetylgalactosaminyl-peptides isolated were judged to be polydisperse by gel filtration, and ion-exchange chromatography divided the glycopeptide population into several fractions with differing amino acid compositions. A Lumbricus terrestris hexosaminidase preparation was successful in removing almost all the remaining sugar from the glycopeptides, but caused further rupture of the peptide. When a per O-acetylated glycoprotein was treated with the H2SO4/acetic acid reagent the glycopeptide contained, in addition to N-acetylgalactosamine, about 50% of the sialic acid present in the parent glycoprotein, indicating that most of this sugar is located near the peptide end of the carbohydrate chains.     

Studies on glycopeptides derived from acidic glycoproteins of guinea-pig serum

1. Fraction I, a fraction containing acidic glycoproteins, isolated from guinea-pig serum, was digested with Pronase after removal of sialic acid and a major and a minor glycopeptide fraction were isolated by chromatography with Sephadex G-25 and G-50. 2. The major fraction was examined by various methods and shown to contain several glycopeptides. Estimates of molecular weight of the glycopeptide fractions were obtained. Although some variation appeared to occur, the glycopeptides were not grossly heterogeneous with respect to size. An average prosthetic group was estimated to contain about 15 sugar residues. 3. Aspartic acid was the principal amino acid present in the fractions and in all subfractions of the major fraction investigated. Where examined, ammonia was liberated on acid hydrolysis in approximately equimolar amounts to the aspartic acid present. The carbohydrate composition of the fractions was also determined. 4. The glycopeptides showed relatively little degradation in alkaline solution. 5. These results suggest that an N-acylglycosylamine bond involving aspartic acid forms the major type of linkage between carbohydrate and polypeptide. The isolation of a compound with the composition and chromatographic properties of 2-acetamido-1-(l-beta-aspartamido)-1,2-dideoxy-beta-d-glucose supports this view, and indicates that N-acetylglucosamine is the sugar involved in at least many linkages. 6. Fraction I contains some glycoproteins that are susceptible to Pronase and one or more others that resist digestion before the removal of sialic acid. A brief examination revealed some similarities between prosthetic groups derived from both kinds of glycoprotein.     

Characterization of the oligosaccharide units of the bovine erythrocyte membrane glycoprotein.

The major glycoprotein of the bovine erythrocyte membrane was purified by extraction of the ghosts with lithium 3,5-diiodosalicylate followed by phenol-water extraction and acidification. The glycoprotein contains 20% protein and 80% carbohydrate by weight and gives a single band on sodium dodecyl sulfate-polyacrylamide gels with an estimated molecular weight of 230000 daltons. The carbohydrate composition of the glycoprotein was determined to be (in residues relative to sialic acid): sialic acid, 1.0; fucose, less than 0.01; mannose, 0.1; galactose, 3.3; N-acetylgalactosamine, 0.9; and N-acetylglucosamine, 2.4. Pronase digestion of the isolated glycoprotein followed by Sephadex G-75 gel filtration resulted in the separation of a small pool of glycopeptides (pool III), which included all of the mannose-containing glycopeptides, from the bulk of the glycopeptide material which was in the void fractions of the column (pool I). Alkaline borohydride treatment released over 95% of the oligosaccharide units in pool I and approximately 30% of the oligosaccharide units in pool III. These oligosaccharides were isolated by gel filtration and ion-exchange chromatography. The oligosaccharides released from pool I had molecular weights of 1100-1400 daltons and contained sialic acid, galactose, and N-acetylglucosamine in molar ratios of 0.5-1:3:2 as well as a partial residue of N-acetylgalactosaminitol. The oligosaccharides released from pool III by alkali had molecular weights of 1300-1600 daltons and contained sialic acid, galactose, N-acetylglucosamine, N-acetylgalactosamine and N-ACETYLgalactosaminitol in molar ratios of 1-2:2:1:1:1. These data indicate that the majority of the oligosaccharide units of the bovine erythrocyte glycoprotein are linked O-glycosidically to the peptide backbone of the molecule.     

Characterization and partial purification of beta-N-acetylgalactosaminyltransferase from urine of Sd(a+) individuals

Urine from Sd(a+) individuals was found to contain a beta-N-acetylgalactosaminyltransferase that transfers N-acetylgalactosamine (GalNAc) from UDP-GalNAc to 3'-sialyllactose and glycoproteins carrying the terminal NeuAc alpha-3Gal beta group. This enzyme has been purified 174-fold by affinity chromatography on Blue Sepharose and DEAE-Sephacel chromatography in a yield of 33%. Neither endogenous incorporation nor sugar nucleotide degrading enzymes were found in the purified preparation. The transferase had a pH optimum of pH 7.5 and a requirement for Mn2+ but not for detergents. The Km for UDP-GalNAc was 66 X 10(-6) M, using fetuin as an acceptor. Like beta-GalNAc-transferase from other sources the urinary enzyme had a strict requirement for sialylated acceptors. On the basis of enzymatic and chemical treatment of the product obtained by the transfer of [3H]GalNAc to 3'-sialyllactose, we propose that the enzyme attaches GalNAc in beta-anomeric configuration to O-4 of the galactose residue that is substituted at O-3 by sialic acid. A preparation of Tamm-Horsfall glycoprotein from a Sd(a-) donor lacking beta-GalNAc was found to be the best acceptor among the glycoproteins tested. Studies on the transferase activity toward fetuin, human chorionic gonadotropin, and glycophorin A indicated that the enzyme preferentially adds the sugar to the sialylated terminal end of N-linked oligosaccharides. Unlike the beta-GalNAc-transferase bound to human kidney microsomes (F. Piller et al. (1986) Carbohydr. Res. 149, 171-184) the urinary transferase is able to transfer beta-GalNAc to the NeuAc alpha-3Gal beta-3(NeuAc alpha-6)GalNAc chains bound to the native glycophorin.     

Carbohydrate Structure of Sindbis Virus Glycoprotein E2 from Virus Grown in Hamster and Chicken Cells

Sindbis virus was used as a probe to examine glycosylation processes in two different species of cultured cells. Parallel studies were carried out analyzing the carbohydrate added to Sindbis glycoprotein E2 when the virus was grown in chicken embryo cells and BHK cells. The Pronase glycopeptides of Sindbis glycoprotein E2 were purified by a combination of ion-exchange and gel filtration chromatography. Four glycopeptides were resolved, ranging in molecular weight from 1,800 to 2,700. Structures are proposed for each of the four glycopeptides, based on data obtained by quantitative composition analyses, methylation analyses, and degradation of the glycopeptides using purified exo- and endoglycosidases. The largest three glycopeptides (S1, S2, and S3) have similar structures but differ in the extent of sialylation. All three contain N-acetylglucosamine, mannose, galactose, and fucose, in a structure similar to oligosaccharides found on other glycoproteins. Glycopeptide S1 has two residues of sialic acid, whereas glycopeptides S2 and S3 contain 1 and 0 residues of sialic acid, respectively. The smallest glycopeptide, S4, contains only N-acetyglucosamine and mannose, and is also similar to mannose-rich oligosaccharides found on other glycoproteins. Each of the complex glycopeptides (S1, S2, or S3) from virus grown in BHK cells is indistinguishable from the corresponding glycopeptides derived from virus grown in chicken cells. Glycopeptide S4 is also very similar in size, composition, and sugar linkages from virus derived from the two hosts. These results suggest that chicken cells and BHK cells have similar glycosylation mechanisms and glycosylate Sindbis glycoprotein E2 in nearly identical ways.     

Purification and composition of the proteins from Sindbis virus grown in chick and BHK cells.

Procedures are described for the purification of the Sindbis virus structural proteins. The amino acid and carbohydrate compositions of the purified proteins are presented for virus grown in BHK-21/13 and chicken embryo cells. Glycoprotein E1 from virus grown in BHK cells is deficient in a mannose-rich glycopeptide found on that glycoprotein when virus is grown in chicken embryo cells. The complex glactose-containing glycopeptides appear similar for virus grown in both hosts. However, when virus is grown in BHK cells, both glycoproteins are enriched in those glycopeptides containing more sialic acid. Since the two viral glycoproteins are difficult to separate cleanly during purification, it is suggested that there may be strong, but noncovalent, interactions between glycoproteins E1 and E2. It is also suggested that there may be an interaction between glycoprotein E2 and a component of the nucleocapsid.     

Preparation of glycopeptides and oligosaccharides from thyroxine-binding globulin.

Over 99% of thyroxine (T4), the major form of thyroid hormone in plasma, is bound to the plasma glycoprotein thyroxine-binding globulin (TBG). The carbohydrate composition of TBG (14.6% by weight) consists of mannose, galactose, N-acetylglucosamine, and N-acetylneuraminic acid in the molar ratios of 11:9:16:10 per mol of glycoprotein. No fucose or N-acetylgalactosamine were detected. Amino acid analyses were performed. Glycopeptides, prepared by exhaustive pronase treatment of the glycoprotein, were separated by gel filtration and ion exchange chromatography. All glycopeptides contained the four sugars present in the native glycoprotein. One-fourth of the glycopeptide fraction was resolved into a discrete component, glycopeptide I. The remaining glycopeptides were a mixture termed glycopeptides II and III. Glycopeptides II and III were resolved into two discrete carbohydrate units, termed oligosaccharides A and B, by alkaline-borohydride treatment and DEAE-cellulose chromatography. We propose that TBG contains four oligosaccharide chains as calculated from the molecular weights of the glycopeptides and from compositional data assuming 1 asparagine residue/glycopeptide. The carbohydrate structures of the glycopeptides and relative affinities of TBG, glycopeptides and oligosaccharides for hepatocyte plasma membrane binding are presented in the accompanying paper (Zinn, A.B., Marshall, J.S., and Carlson, D.M. (1978) J. Biol. Chem. 253, 6768-6773.     

Glycopeptide fractions prepared from purified central and peripheral rat myelin

Myelin was purified from rat brain and sciatic nerve after invivo labeling with [³H]fucose and [¹⁴C]glucosamine to provide a radioactive marker for glycoproteins. The glycoproteins in the isolated myelin were digested exhaustively with pronase, and glycopeptides were isolated from the digest by gel filtration on Bio-Gel P-10. The glycopeptides from brain myelin separated into large and small molecular weight fractions, whereas the glycopeptides of sciatic nerve myelin eluted as a single symmetrical peak. The large and small glycopeptide fractions from central myelin and the single glycopeptide fraction from peripheral myelin were analyzed for carbohydrate by colorimetric and gas liquid chromatographic techniques. The glycopeptides from brain myelin contained 2.4 μg of neutral sugar and 0.59 μg of sialic acid per mg total myelin protein, whereas sciatic nerve myelin glycopeptides contained 10 μg of neutral sugar and 3.8 μg of sialic acid per mg total protein. Similarly, the gas-liquid chromatographic analyses showed that the glycopeptides from peripheral myelin contained 4- to 7-fold more of each individual per mg total myelin protein than those from central myelin. Most of the sialic acid and galactose in the glycopeptides from central myelin were in the large molecular weight fraction, and the small molecular weight glycopeptides contained primarily mannose and $\text{N-}\text{acetylglucosamine}$. The considerably higher content of glycoprotein-carbohydrate in peripheral myelin supports the results of gel electrophoretic studies, which indicate that the major protein in peripheral myelin in glycosylated while the glycoproteins in purified central myelin are quantitatevely minor components.     

Characteristics of a mucin-type sialoglycopeptide produced by B16 mouse melanoma cells.

The glycopeptides produced by B16 mouse melanoma cells grown in the presence of [³H]glucosamine were isolated and fractionated into two classes (I and II) with cetyl pyridinium chloride. The class I glycopeptides were of higher molecular weight and of higher negative charge (sialic acid content) than those in class II. Class I glycopeptides contained N-acetyl neuraminic acid, galactose and N-acetylgalactosamine and on treatment with alkaline-borohydride were degraded to apparently tri- and tetrasaccharides. The presence of this mucin-type glycoprotein on the cell surface was detected by mild trypsinization of intact cells.     

Synthesis of tumor-associated glycopeptide antigens

Carbohydrates and peptides linked together in glycoproteins constitute important components of the molecular communication between cells in multicellular organisms. Cell morphogenesis and tumorigenesis are accompanied by changes in the glycoprotein profiles of the outer cell membranes. Glycopeptide fragments of glycoproteins that have altered structures in tumor cells are of interest as tumor-associated antigens for the distinction between normal cells and tumor cells. In contrast to glycoproteins isolated from biological sources, synthetic glycopeptides are obtained in pure form and exactly specified structures. The methods developed for the synthesis of glycopeptides with tumor-associated antigen structure are outlined in this article by means of a series of typical examples. Beginning with O-glycopeptides of the relatively simple alpha-O-galactosamine-serine/threonine (T(N)-antigen) type, glycopeptide antigens of increasing complexity are described. The review includes syntheses of the saccharide components, the glycosylation reactions to furnish the O-glycosyl amino acid building blocks, their selective C- and N-terminal deprotection and the use of these building blocks for glycopeptide syntheses both in solution and on the solid support. Particular attention is given to glycopeptides containing sialic acid residues, whose syntheses are demanding since reversible protection of the sialic carboxylic group is required. Synthetic methods for the construction of N-glycopeptides carrying the important cell adhesion ligands sialyl Lewis x and sialyl Lewis a antigen are also described. Strategies for the construction of glycopeptides of this type require methods compatible with the presence of the sialic acid residue, as well as with the acid-sensitivity of the fucoside bonds.     

Purification of a sialic acid-specific lectin from the Indian scorpion Heterometrus granulomanus

A sialic acid-specific lectin, scorpin, has been purified to apparent homogeneity from the Indian scorpion Heterometrus granulomanus by affinity chromatography on equine submandibular gland glycopeptides linked to Sepharose and gel filtration on Sephadex G-200. The lectin has a molecular mass of 500 000 Da and was dissociated into single polypeptide chains of 15 000 Da, as determined by SDS gel electrophoresis in the presence of 2-mercaptoethanol. Scorpin is a glycoprotein containing 2.8% sugars. Its specificity was investigated by the inhibition of hemagglutination with various derivatives of sialic acid and other sugars. N-Acetylneuraminic acid gave better inhibition than N-glycoloylneuraminic acid but showed less inhibitory effect than sialyl-alpha(2----3)-lactose and disialyllactose. Among the sialoglycoconjugates tested, equine submandibular gland glycopeptide was found to be the most potent inhibitor. Scorpin showed a strong tendency to bind to carboxyl groups, since reduction of the carboxyl group of N-acetylneuraminic acid destroyed the inhibitory potency of this sugar. Furthermore, D-glucuronic acid inhibited hemagglutination whereas N-acetylglucosamine or N-acetylgalactosamine were not inhibitors.     

Morphological and conformational studies of Tamm-Horsfall urinary glycoprotein

We have studied the circular dichroic properties of normal and cystic fibrotic Tamm-Horsfall urinary glycoproteins, and the asialo-derivatives (ca. 80% removal of sialic acid with neuraminidase). There was no evidence of α-helicity in Tamm-Horsfall urinary glycoprotein, but the results do indicate a significant amount of β-structure. The circular dichroic spectra of normal and cystic fibrotic Tamm-Horsfall urinary glycoproteins and the asialo-derivatives were identical, thus suggesting that there is no major difference in the ordered secondary structure of Tamm-Horsfall urinary glycoprotein in cystic fibrosis (relative to normal Tamm-Horsfall urinary glycoprotein), and that sialic acid exerts no major effect on the β-structure. Also, the circular dichroic spectrum of Tamm-Horsfall urinary glycoprotein was not affected by Ca²⁺ at concentrations just below that required for gel formation. Electron microscopic studies reveal the presence of a supramolecular helical structure arising from subunit interactions. This structure was characterized by a repeat of 120–130 Å and a minimal helix diameter of ca. 40 Å, although this value varied depending on the number of interacting helices. The helical structure was observed for normal, cystic fibrotic, and asialo derivatives of Tamm-Horsfall urinary glycoproteins, and was independent of added Ca²⁺. Guanidine hydrochloride treatment, followed by dialysis, irreversibly destroyed this supra-molecular helical structure, but the β-structure was partially restored, as indicated by the circular dichroic spectrum. The Ca²⁺-mediated gel formation was found to be inhibited in asialo-Tamm-Horsfall urinary glycoprotein.     

Sialylated oligosaccharides O-glycosidically linked to glycoprotein C from herpes simplex virus type 1.

Glycoprotein C (gC) was purified by immunoabsorbent from herpes simplex virus type-1-infected BHK cells labeled with [14C]glucosamine for 11 h and chased for 3 h. Glycopeptides obtained by pronase digestion of gC were fractionated by Bio-Gel filtration and concanavalin A-Sepharose chromatography. Each glycopeptide fraction was analyzed for amino sugar composition by thin-layer chromatography. The majority of radioactivity was recovered as N-acetylglucosamine, but a significant amount of labeled N-acetylgalactosamine was detected and recovered preferentially in some glycopeptide species. Mild alkaline borohydride treatment of the glycopeptides resulted in the release of small degradation products which contained N-acetylgalactosaminitol as the major labeled component and a drastic reduction of N-acetylgalactosamine in the residual glycopeptides. These results demonstrated that gC carries O-glycosidically linked oligosaccharides in addition to the N-linked di- and triantennary glycans previously described (F. Serafini-Cessi, F. Dall'Olio, L. Pereira, and G. Campadelli-Fiume, J. Virol. 51:838-844, 1984). Chromatographic behavior on DEAE-Sephacel chromatography and neuraminidase digestion of O-linked oligosaccharides indicated the presence of two major sialylated species carrying one and two sialic acid residues, respectively. The characterization of a peculiar glycopeptide species supported the notion that some of the O-linked oligosaccharides are bound to a cluster of hydroxyamino acids located near an N-glycosylation site which carries one N-linked diantennary oligosaccharide.     

Isolation and partial characterization of the major sialoglycoprotein of human T-lymphoblastoid cells of a MOLT-4B cell line.

A sialoglycoprotein with an approx. mol.wt. of 95000 was isolated from human lymphoblastoid cells of a MOLT-4B cell line, which was of human T-lymphocyte origin, by ion-exchange chromatography, affinity chromatography on a column of wheat-germ agglutinin-Sepharose and preparative slab-gel electrophoresis. The localization of this glycoprotein on the cell surface was indicated by surface labelling by the periodate/NaB3H4 and lactoperoxidase-catalysed iodination methods. Carbohydrate analyses of this glycoprotein revealed that its total carbohydrate content is 28% (w/w), and it contains fucose, galactose, mannose, N-acetylglucosamine, N-acetylgalactosamine and sialic acid in molar proportions 1.0:4.0:3.7:3.5:1.2:2.5, suggesting that it has two types of sugar chain, i.e. sugar chains like those of serum glycoproteins and sugar chains of the type found in mucins. Actually, alkaline borohydride treatment of this glycoprotein yielded tri- and tetra-saccharide, the latter containing 1 molecule of fucose in addition to each molecule of galactose, N-acetylgalactosamine and sialic acid. This glycoprotein bound to Ricinus communis agglutinin and concanavalin A as well as to wheat-germ agglutinin.     

Effects of pronase and neuraminidase treatment on a myelin-associated glycoprotein in developing brain.

Rats (14 days old) were injected with [14c]fucose and young adult rats with [3H]fucose in order to label the myelin-associated glycoproteins. As previously reported, the major [14C]fucose-labelled glycoprotein in the immature myelin had a higher apparent molecular weight on sodium dodecyl sulphate/polyacrylamide gels that the [3H]fucose-labelled glycoprotein in mature myelin. This predominant doubly labelled glycoprotein component was partially purified by preparative gel electrophoresis and converted to glycopeptides by extensive Pronase digestion. Gel filtration on Sephadex G-50 separated the glycopeptides into several clases, which were designted A,B, C AND D, from high to low molecular weight. The 14C-labelled glycopeptides from immature myeline were enriched in the highest-molecular-weight class A relative to the 3H-labelled glycopeptides from mature myelin. Neuraminidase treatment of the glycoprotein before Pronase digestion greatly decreased the proportion of glycopeptides fractionating in the higher-molecular-weight classes and largely eliminated the developmental differences that were apparent by gel filtration. However, neuraminidase treatment did not decrease the magnitude of the developmental difference revealed by electrophoresing the intact glycoprotein on sodium dodecyl sulphate gels, although it did decrease the apparent molecular weight of the glycoprotein from both the 15-day-old and adult rats by an amount comparable in magnitude to that developmental difference. The results from gel filtration of glycopeptides indicate that there is a higher content of large molecular weight, sialic acid-rich oligosaccharide units in the glycoprotein of immature myelin. However, the higher apparent molecular weight for the glycoprotein from 15-day-old rats on sodium dodcyl sulphate gels is not due primarily to its higher sialic acid content.     

Identification of intrinsic sialidase and sialoglycoprotein substrates in rat brain synaptic junctions

Sialidase activity associated with rat brain synaptic junctions (SJ) and synaptic membranes (SM) was determined. Both fractions released sialic acid from exogenous glycopeptides and gangliosides. SJ accounted for 5-10% of the total sialidase activity recovered from SM following extraction with Triton X-100, and the specific activity of SJ sialidase was 60% of that of the parent SM fraction. Intrinsic SJ sialidase hydrolysed 12-15% of the sialic acid associated with endogenous SJ glycoproteins. Sialic acid residues associated with SJ glycoproteins were labelled with sodium borotritide and SJ proteins fractionated by affinity chromatography on concanavalin A-agarose. SJ glycoproteins that reacted with concanavalin A (con A+ glycoproteins) accounted for 25% of the total SJ [3H]sialic acid. Intrinsic SJ sialidase hydrolysed 20% of the [3H]sialic acid associated with these glycoproteins. Each molecular weight class of con A+ glycoprotein previously shown to be a specific component of the postsynaptic apparatus contained sialic acid and was acted on by intrinsic SJ sialidase.     

Carbohydrate structure of the major glycopeptide from human cold-insoluble globulin

Cold-insoluble globulin (CIg) is a member of a group of circulating and cell-associated, high-molecular-weight glycoproteins termed fibronectins. CIg was isolated from human plasma by affinity chromatography on gelatin-Sepharose. SDS-polyacrylamide gel electrophoresis of the purified glycoprotein gave a double band that migrated near myosin. The CIg glycopeptides were released by pronase digestion and isolated by chromatography on Sephadex G-50. Affinity chromatography of the major G-50 peak on Con A-Sepharose resulted in two fractions: one-third of the glycopeptides were unbound and two-thirds were weakly bound (WB). Sugar composition analysis of the unbound glycopeptides by GLC of the trimethylsilyl methyl glycosides gave the following molar ratios: sialic acid, 2.5; galactose, 3.0; N-acetylglucosamine, 4.9; and mannose, 3.0. Sugar composition analysis of the WB glycopeptides gave the following molar ratios: sialic acid, 1.7; galactose, 2.0; N-acetylglucosamine, 4.1; and mannose, 3.0. The WB CIg glycopeptides cochromatographed on Sephadex G-50 with WB transferrin glycopeptides giving an estimated molecular weight of 2,800. After degradation with neuraminidase alone or sequentially with β-galactosidase the CIg and transferrin glycopeptides again cochromatographed. Methylation linkage analysis of the intact and the partially degraded glycopeptides indicated that the carbohydrate structure of the major human CIg glycopeptide resembles that of the major glycopeptide from transferrin.     

Substrate specificity of cerebral GDP-fucose: glycoprotein fucosyltransferase

Solubilized sheep brain fucosyltransferase was shown to transfer fucose from GDP-fucose onto glycoprotein and glycopeptide acceptors, such as asialofetuin, asialotransferrin, their glycopeptides and glycopeptides from ovalbumin, but not on to monosaccharides and disaccharides such as galactose, N-acetylglucosamine and lactose. Competition studies between asialofetuin and glycopeptide V from ovalbumin provided evidence that both substrates compete for a common enzyme active site. The position of the fucosyl linkage was then investigated. Endo-beta-N-glucosaminidase D digestion of fucosylated and acetylated glycopeptide V showed that fucose is not linked to asparagine-linked N-acetylglucosamine. Hydrazinolysis and nitrous acid deamination performed on asialofetuin and glycopeptide V proved that fucose is not linked to external galactose or N-acetylglucosamine either. Thus we assume that fucose is linked to the oligomannochitobiosyl core of the glycan, and probably to the second N-acetylglucosamine.     

Comparison of Membrane Protein Glycopeptides of Sindbis Virus and Vesicular Stomatitis Virus

A comparison has been made of the membrane glycoproteins and glycopeptides from two enveloped viruses, Sindbis virus and vesicular stomatitis virus (VSV). Glycopeptides isolated from Sindbis virus and VSV grown in the same host appear to differ principally in the number of sialic acid residues per glycopeptide; when sialic acid is removed by mild acid treatment, the glycopeptides of the two viral proteins are indistinguishable by exclusion chromatography. Preliminary evidence argues that the carbohydrate moiety covalently bound to different virus-specified membrane proteins may be specified principally by the host.     

Glycosylation sites of vesicular stomatitis virus glycoprotein.

Detailed analysis on DEAE-Sephadex of the tryptic digestion products of the glycoprotein from vesicular stomatitis virus grown in HeLa suspension cultures revealed the presence of two major and several minor sugar-labeled species. The minor tryptic glycopeptides were converted to one of the two major glycopeptide species by treatment with neuraminidase. Thus, vesicular stomatitis virus glycoprotein contains only two oligosaccharide side chains that are heterogeneous in their sialic acid content.