Carbohydrate structure and serological behaviour of "antifreeze" glycoproteins from an Antarctic fish

Comparison of alkal-labile oligosaccharide chains of M and N blood-group glycopeptides from human erythrocyte membrane

Alkali-borohydride degradation of M or N blood-group active, tryptic glycopeptides and glycoproteins was performed under conditions giving the reduced oligosaccharides in a yield significantly improved over that reported earlier. Degradation of desialosylated glycoproteins yielded beta-D-Galp-(1 leads to 3)-D-GalNAcol, D-GalNA-col, and Galol in a ratio of approximately 30:1:1. GalNAc was shown to be alpha-D-linked to the polypeptide chain. Degradation of the glycopeptides gave the tetrasaccharide, NeuAc-(2 leads to 3)-beta-D-Galp-(leads to 3)-[NeuAc-(2 leads to 6)]-D-GalNAcol, and two trisaccharides, NeuAc-(2 leads to 3)-beta-D-Galp-(1 leads to 3)-D-GalNAcol and beta-D-Galp-(1 leads to 3)-[NeuAc-(2 leads to 6)]-D-GalNAcol, in a molar ratio of approximately 8:3:1. These oligosaccharides were accompanied by minor amounts of unidentified compounds showing identical electrophoretic mobility when derived from M and N glycopeptides. During isolation of the reduced oligosaccharides, the release of sialic acid did not exceed 5.5%, indicating that only a part of the trisaccharide portion might have arisen as a result of desialosylation of the tetrasaccharide. No differences between the degradation products derived from M and N glycoproteins were found, and the presence of significant amounts of larger, alkali-labile oligosaccharides was not observed.

Studies on the fate of defined asialoglycoproteins in the circulation of the mouse

Asialoglycoproteins injected into the tail vein of mice accumulated rapidly in the liver, as found in rats and rabbits by other authors, whereas the native glycoprotein remained in the serum for much longer periods of time. Histological examination of liver sections after the injection of radiolabelled asialoglycoproteins failed to show any binding to the hepatocyte membrane. However, silver grains were observed in the sinuses of the liver and often appeared to be bound to the sinus wall. In addition, small amounts of label in the reticulo-endothelial system of the spleen were observed. A comparison in the uptake of asialoglycoproteins by the liver, between those with alkali-labile galactose-containing (AL) chains and those with alkali-stable galactose-containing (AS) chains, showed that the former were taken up more slowly. There was no correlation between total galactose content and rate of hepatic uptake. Asialoglycoproteins with AS chains could not inhibit the uptake in the liver of those with AL chains. However, when the order was reversed, the uptake of AS containing asialoglycoproteins was inhibited by 50%. Different mechanisms to explain these results are discussed.

A new marker for neuraminidase-treated human serum glycoproteins from the haemolymph of Tridacna maxima (Röding)

Highly purified human serum glycoproteins were treated with neuraminidase. The exposed subterminal carbohydrate structures reacted strongly with an anti-galactan precipitin from the haemolymph of Tridacna maxima which detects terminal, non-reducing beta-D-galactoside residues. This invertebrate precipitin, Tridacnin, may be used as a marker for nearly two thirds of all asialo serum glycoproteins; A number of different cross-reactions with various other polysaccharides and galactans subdivides those neuraminidase-treated glycoproteins into several subgroups, indicating that the uncovered carbohydrate structures are not always completely identical. In this way, together with the cross-reacting precipitins from plant and invertebrate origin. Tridacnin may be a useful tool for elucidating and establishing the structure of the carbohydrate part of serum glycoproteins.

Studies on the membrane glycoprotein defect of En(a-) erythrocytes. I. Biochemical aspects

Discontinuous sodium dodecylsulphate-polyacrylamide gel electrophoresis, followed by periodic acid/Schiff or Coomassie staining and densitometry, spectrophotometric and gas-liquid chromatographic carbohydrate analyses as well as heterophile agglutinins are employed to study the nature of the membrane glycoprotein defect in En(a-) erythrocytes from Finland and England, heterozygous Ena red cells from Finland and the erythrocytes of two individuals from Switzerland. The results suggest that En(a-) cells lack the major membrane sialoglycoprotein, the so-called MN glycoprotein. Heterozygous Ena erythrocytes from Finland and those from Switzerland have only about half of the normal amount of MN glycoprotein. The molecular weight of the major Coomassie staining membrane protein (component III) is increased by approx. 5000 and 3000 daltons in En(a-) and the other red cells respectively. Some aspects of this membrane defect are discussed.

Immunochemical studies on the specificity of the peanut (Arachis hypogaea) agglutinin

The specificity of purified, peanut agglutinin has been studied immunochemically by quantitative precipitin and inhibition assays. The lectin showed substantial differences in precipitating with blood-group substances of the same specificity. Of the B substances tested, horse 4 25% completely precipitated the lectin, Beach phenol insoluble failed to interact, and PM phenol insoluble gave an intermediate reaction. The lectin did not precipitate with A1 substances, with hog gastric mucin A + H substance, or with A2 substance WG phenol insoluble. Another A2 substance, cyst 14 phenol insoluble, precipitated approximately 2/3 of the lectin. Of the H substances, Tighe phenol insoluble was inactive, JS phenol insoluble precipitated poorly, and morgan standard H precipitated about 80% of the lectin. However, first stage of Smith degradation, as well as Pl fractions obtained by mild acid hydrolysis of blood-group substances, gave products which precipitated strongly. The lectin was also completely precipitated by all precursor blood-group substances, as well as by cows 21 and 26, all having strong I-Ma, I-Ort, I-Step, and I-Da activities. Cow 18, which does not possess significant blood-group I activity, precipitated very slightly. Fractions of blood-group substances N-1 (Lea) and Tij (B) obtained by precipitation from 90 percent phenol at higher concentrations of ethanol interacted better with peanut agglutinin. These differences in activity are ascribable to a heterogeneity resulting from incomplete biosynthesis of carbohydrate side-chains of blood-group substances, particularly resulting in variations in the numbers of DGalbeta1 leads to 3DGalNAc or DGalbeta1 leads to 4DGlcNAc determinants. The agglutinin reacted with the hydatid cyst P1 glycoprotein, as well as with the previously studied antifreeze and sialic acid-free alpha1 acid glycoproteins, but not with pneumococcus type XIV polysaccharide. Inhibition of precipitation showed the lectin to be most specific for the disaccharide DGalbeta1 leads to 3DGalNAc, which is 14, 55, and 90 times as active as DGalbeta1 leads to 4DGlcNAc, DGal, and DGalbeta1 leads to 3DGlcNAc, respectively. DGalbeta1 leads to 3N-acetyl-D-galactosaminitol has approximately 1/25th the activity of DGalbeta1 leads to 3DGalNAc. Substitutions of DGlcNAc or LFuc on the DGal of active inhibitors completely blocked the activity, in line with the assumption that the combining site of the peanut lectin is a partial cavity. The oligosaccharides DGalbeta1 leads to 4DGlcNAcbeta1 leads to 6-hexane-1,2,4,5,6-pentol(s) and DGalbeta1 leads to 3[DGalbeta1 leads to 4DGlcNAcbeta1 leads to 6]N-acetyl-D-galactosaminitol showed the same inhibitory activity as DGalbeta1 leads to 4DGlcNAc, suggesting that the combining site of the peanut agglutinin may not be complementary to more than a disaccharide...

Alkali-labile oligosaccharides from glycoproteins of different erythrocyte and milk fat globule membranes

Phenol extraction of horse, sheep, cow, pig and human erythrocyte membranes and human milk fat globule membranes gave glycoprotein fractions, all of which were shown by gas chromatography to contain the reduced disaccharide beta-D-galactosyl (1-3)-N-acetyl-D-galactosaminital after treatment with alkaline borohydride. Cow and pig erythrocyte membrane glycoproteins were found however to contain much lower amounts than the erythrocyte membrane glycoproteins of the other species tested. After gel filtration, a tetrasaccharide was isolated from horse and sheep glycoproteins containing the disaccharide plus two molecules of sialic acid. Periodate oxidation together with paper chromatography of alkaline degraded fragments showed these two molecules of sialic acid to be linked to positions C3 and C6 of the galactosyl and N-acetylgalactosamine residues respectively. Evidence was obtained for a similar structure from pig and cow erythrocyte glycoproteins and human milk fat globule membrane glycoproteins although the complete structure was not elucidated. In all native glycoprotein fractions, the unsubstituted disaccharide beta-D-galactosyl (1-3)-N-acetyl-D-galactosamine was found to be present to different extents. Haemagglutination inhibition tests against human anti-T serum, Arachis hypogoea and Vicia graminea by desialylated glycoproteins showed the presence of the T-antigen, confirming the chemical findings. Inhibition was found to be proportional to the chemically detected amounts of disaccharide in each fraction. Evidence for a second carbohydrate chain in horse, sheep and human erythrocyte glycoproteins with a sialic acid substituted N-acetylgalactosamine residue as the terminal sequence was obtained using the agglutinin from Helix pomatia.

Binding of human hemoglobin and its polypeptide chains with haptoglobin coupled to an agarose matrix

The interactions of human haptoglobin covalently linked to agarose with human hemoglobin and with p-chloromercuribenzoic-acid-treated alpha and beta chains (alpha* and beta* chains) were studied by flow chromatography and equilibrium binding. The results indicate that in solid state, haptoglobin maintains the same binding characteristics as in solution, the order of binding affinities being: hemoglobin greater than alpha* chain greater than beta* chain. The study of the binding parameters of the alpha* chain shows an heterogeneity of binding sites on the haptoglobin and an average affinity constant Ka of 3.6 X 10(4)l/mol.

Immunochemical detection of the Thomsen-Friedenreich antigen (T-antigen) on the pig lymphocyte plasma membrane

A method for the isolation of lymphocytes from pig peripheral blood and preparation of plasma membranes was developed. The method resulted in a ten-fold increase in 5'-nucleotidase activity and neuraminic acid, relative to protein. A cholesterol/phospholipid ratio of 0.93 was obtained. Alkaline borohydride treatment of isolated plasma membrane, after desialylation, released the disaccharide beta-D-galactosyl-(1 leads to 3)-N-acetyl-D-galactosaminitol (the immunodominant group of the T-antigen), which was identified by gas chromatography using a crystalline standard. The disaccharide was not found without prior desialylation, indicating that all the disaccharide units were substituted by neuraminic acid. Serological evidence using the agglutinins from Arachis hypogoea and Helix pomatia confirmed the presence of this disaccharide (T-antigen) in the lymphocyte membrane and indicated that it was the major alkali-labile oligosaccharide of the pig lymphocyte membrane.

Studies on the receptors of the MNSs group system

Results with modified human red cell membrane sialoglycoproteins indicate that alkali-labile sialic acid and amino groups are parts of the erythrocyte receptor sites recognized by common rabbit and human anti-M and -N sera. The "N" antigen, demonstrable in MM glycoprotein preparations by rabbit anti-N, has structural properties which are similar to those of the MN receptors. Sialic acid, amino groups and carbohydrate, susceptible to periodate oxidation, are not involved in the Ss antigen sites. The specificity of the Vicia graminea lectin is dependent on free amino and carboxyl groups. Its affinity for the substances is increased by blocking of amino groups.