Binding of human fibroblast interferon to concanavalin A-agarose. Involvement of carbohydrate recognition and hydrophobic interaction.

Human fibroblast interferon binds to a concanavalin A-agarose (Con A-Sepharose) equilibrated with methyl alpha-D-mannopyranoside, or levan; in contrast, it is only partially retarded on a similar column equilibrated with ethylene glycol. Interferon does not bind, however, to a lectin column equilibrated with both methyl alpha-D-mannopyranoside and ethylene glycol. Thus, a hydrophobic interaction between fibroblast interferon and the immobilized lectin seems to account for a large portion of the binding forces involved. Other hydrophobic solutes, such as dioxane, 1, 2-propanediol, and tetraethylammonium chloride, were found equally or more efficient than ethylene glycol in displacing interferon from the lectin column. The elution pattern of interferon from a concanavalin A-agarose (Con A-Sepharose) column, at a constant ehtylene glycol concentration and with an increasing mannoside concentration, reveals the existence of four distinct interferon components. The selective adsorption to and elution from a concanavalin A-agarose (Con A-Sepharose) column resulted in about a 3000-fold purification of human fibroblast interferon and complete recovery of activity. The specific activity of the partially purified interferon preparation is about 5 X 10(7) units per mg of protein. The chromatographic behavior of human leukocyte interferon is remarkable in that it does not bind to concanavalin A-agarose at all indicating the absence of carbohydrate moieties recognizable by the lectin, or if present, their masked status. When concanavalin A was coupled to an agarose matrix (cyanogen bromide activated) at pH 8.0 and 6.0 human fibroblast interferon bound to both lectin-agarose adsorbents and could be recovered with methyl alpha-D-mannopyranoside. Concanavalin A, immobilized directly on agarose matrix at pH 8.0 and 6.0, thus displays only carbohydrate recognition toward interferon. By contrast, unless a hydrophobic solute was included in the solvent containing methyl mannoside, human fibroblast interferon could not be recovered from concanavalin A-agarose coupled at pH 9.0. When concanavalin A was immobilized via molecular arms, in tetrameric as well as dimeric forms, the binding of interferon again occurred exclusively through carbohydrate recognition. Thus, the hydrophobic interaction can be eliminated by appropriate immobilization of the lectin, and then adsorbed glycoproteins, as exemplified here by interferon, can be recovered readily with methyl mannoside alone.     

Affinity of human leukocyte interferon for polyribonucleotides.

Human leukocyte interferon (HL-IF)binds to AGPOLY(A)TM, AGPOLY(U)TM and AGPOLY(I)TM. The bound interferon could be displaced from all three polyribonucleotides by including sodium chloride in the eluant. The nature of interaction of HL-IF with polyribonucleotides is electrostatic and not hydrophobic since its binding was not prevented in the presence of 50% ethylene glycol. The binding of HL-IF on AGPOLY(I)TM is stronger at lower pH since an increase in ionic strength is required to displace it.     

Effect of interferon on the increased reduction of nitroblue tetrazolium (NBT)]

Human leukocyte interferon (HL-IF) enhanced the NBT reduction of human peripheral neutrophil in vitro. Dose relation between IF activity and the NBT reduction was recognized. Heat-inactivated HL-IF, HL-IF neutralized by anti-IF serum or heterologous IF could not increase the NBT reduction.     

Isolation and properties of an NAD- and guanidine-dependent ADP-ribosyltransferase from turkey erythrocytes

An NAD- and guanidine-dependent ADP-ribosyltransferase has been purified more than 500,000-fold from turkey erythrocytes with an 18% yield. The enzyme in the 100,000 X g supernatant fraction was bound to phenyl-Sepharose, eluted with 50% propylene glycol, and further purified by sequential chromatographic steps on carboxymethylcellulose, NAD-agarose and concanavalin A-agarose. The transferase was specifically eluted from concanavalin A-agarose with alpha-methylmannoside. The enzymatic activity was extremely labile following the first purification step. Both propylene glycol and NaCl stabilized the transferase; significant increases in enzyme recovery were obtained by conducting the NAD- and concanavalin A-agarose chromatography in buffer containing propylene glycol. The purified protein exhibits one predominant protein band on SDS-polyacrylamide gels with an estimated molecular weight of 28,300. On Ultrogel AcA54 chromatography, single coincident peaks of ADP-ribosyltransferase activity and protein were observed. Enzyme activity was independent of DNA; the highly purified transferase was inhibited by thymidine, nicotinamide, and theophylline. The specific activity of the purified enzyme (350 mumol of ADP-ribose transferred from NAD to arginine methyl estermin-1mg-1) is comparable to that reported for purified NAD glycohydrolases and poly(ADP-ribosyl)transferases.     

Physico-chemical characterization of hamster interferon.

The glycoprotein nature of Syrian hamster interferon was tested on several immobilized lectins. The specific retention of a small portion (20%) of interferon activity was observed only on concanavalin A-agarose; Component I of the interferon (not retained) has an apparent molecular weight of 23,500 whereas Component II (retained) is larger, 31,500. The apparent hydrophobicity of Syrian hamster interferon was probed by its chromatography on: (a) straight chain hydrocarbons of varied length; (b) aromatic ligands (aminobenzene, benzylamine, beta-phenylethylamine, gamma-phenyl-propylamine); ligands listed in (a) and (b) were immobilized to cyanogen bromide-activated agarose (isourea linkage); and (c) phenyl-agarose (Phenyl-Sepharose CL-4B), an aromatic ligand immobilized via a 2-hydroxypropyl arm to the agarose (ether linkage).     

High molecular weight forms of adrenocorticotropic hormone are glycoproteins.

Mouse pituitary tumor cells (AtT-20/D-16v) were incubated in medium containing [3H] glucosamine or [3H] mannose. By analyzing immunoprecipitates of cell extracts and culture medium it was shown that [3H] glucosamine and [3H] mannose were incorporated into all three high molecular weight forms of ACTH; label was not incorporated into Mr=4,500 ACTH (which is thought to be similar to the 39 amino acid polypeptide form of ACTH, alpha(1-39)). Based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis the apparent molecular weights of these glycoprotein forms of ACTH were 31,000, 23,000, and 13,000. Gel filtration in 6 M guanidine HCl indicated that the molecular weights of these forms of ACTH were substantially lower; sodium dodecyl sulfate-polyacrylamide gel electrophoresis has often been found to overestimate the molecular weight of glycoproteins. A significant fraction of the high molecular weight ACTH in tumor cell extracts binds to columns of concanavalin A-agarose and can be eluted with 0.2 M alpha-methyl-D-mannopyranoside; porcine alpha(1-39) does not bind to concanavalin A-agarose. High molecular weight glycoprotein ACTH can be detected in extracts of mouse and bovine pituitary by using concavalin A affinity chromatography.     

Separation of an isoenzyme of polyphenol oxidase from Duranta plumieri by expanded bed chromatography

Aqueous extracts of seeds of Duranta plumieri were found to be rich in polyphenol oxidase activity. The anion-exchange chromatography of the crude extract on Streamline DEAE resolved the activity into three fractions. The major fraction (77% of the total activity) was further purified by treating it with concanavalin A-agarose in the batch mode. The enzyme preparation eluting with alpha-methylmannoside showed a single band on SDS-PAGE. The minimum molecular weight corresponded to 14,000 Da. The K(m) and V(max) of this isoenzyme were found to be 7.1 mM and 73.5 U ml(-1) min(-1) respectively. The k(cat) of this isoenzyme was calculated to be 8235 s(-1). The isoenzyme also showed the phenomenon of latency and the activity could be enhanced by 196% on heating it at 55 degrees C for 30 min.     

Synthesis and secretion of colonic glycoproteins: Evidence for shedding in vivo of low molecular weight membrane components

In vivo glycoprotein synthesis and secretion was studied in rat colonic epithelial cells using precursor labelling with radiolabelled glucosamine. Sepharose 4B gel filtration of radiolabelled glycoproteins obtained from isolated colonic epithelial cells revealed two major fractions: (1) high molecular weight mucus in the excluded fraction and (2) lower molecular weight glycoproteins in the included volume. These glycoproteins were further fractionated by affinity chromatography on concanavalin A-Sepharose. The low molecular weight [³H]glucosamine-labelled glycoproteins contained a major subfraction which specifically adhered to concanavalin A, and could be eluted with 0.2 M α-methylmannoside. Fractionation of the concanavalin A-reactive glycoproteins on Sephadex G-100 revealed a major peak with a molecular weight of 15 000. In contrast, high molecular weight mucus glycoprotein did not adhere appreciably to concanavalin A-Sepharose. Perfusion experiments indicated that colonic secretions contained both mucus and concanavalin A-reactive glycoproteins. The major concanavalin A-reactive glycoprotein in the colonic perfusate was not derived from serum, but was released directly from the colonic membrane into the lumen.     

Effect of interferon on the inhibition of tumor cell growth by human peripheral leukocytes

Human leukocyte interferon (HL-IF) enhanced the growth inhibition of tumor cells by the human peripheral leukocytes. There was a dose relation between the enhancement of the growth inhibition of tumor cells and the antiviral activity of interferon. When the ratio of lymphocyte to tumor cell was 10:1 or 50:1, it was recognized that HL-IF enhanced the growth inhibition of tumor cells by lymphocyte. The heterologous IFs--mouse and rabbit IFs--or heat-inactivated or trypsinized IF did not enhance the growth inhibition of tumor cells by lymphocytes. RNase treatment did not reduce the antiviral activity and the growth inhibition.     

Large scale purification of human fibroblast interferon

Human fibroblast interferon was partially purified, about 4,000-fold, on a chromatographic tandem of columns: concanavalin A-agarose leads to phenyl-agarose, to a specific activity of ca 4 x 10(7). The overall recovery of interferon activity was ca 60%.     

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.     

Molecular weight of the functional unit of human leukocyte, fibroblast, and immune interferons

There is good agreement between the target molecular weight and the known molecular weight of human leukocyte interferons (about 20,000). The target molecular weight of fibroblast interferon, 31,000 to 42,000, is significantly larger than the monomer molecular weight of 21,000 to 24,000, suggesting that the dimer may be the predominant active functional unit in solution. A range from 63,000 to 73,000 for the target molecular weight of several different fractions of immune interferon (including natural crude as well as the recombinant form) indicates that the functional form of the immune interferon may be a trimer or tetramer. Thus, these studies indicate that the functional unit of leukocyte interferon is the monomer, that of fibroblast interferon is a dimer, and that of immune interferon is probably a tetramer (or trimer).     

Hydrophobic interaction of human, mouse, and rabbit interferons with immobilized hydrocarbons.

Interferons of human, mouse, and rabbit origin bind to straight chain hydrocarbons immobilized on agarose. The hydrophobic nature of binding is established by the following observations: (a) a positive correlation between the length of hydrocarbon ligand and the strength of interaction; (b) a stronger interaction with hydrocarbon ligands terminated with apolar rather than polar head groups; (c) a lack of dependence of binding on ionic strength and pH of the solvent; (d) a reversal of binding by ethylene glycol, a hydrophobic solute; (e) an increasing eluting efficacy of tetraalkylammonium ions with the length of their alkyl substituents. The hydrophobic interactions of human interferon underlie the efficiency of two-step chromatographic procedures. For example, human embryo kidney interferon can be purified about 3,600-fold by sequential chromatography on (a) concanavalin A-agarose, (b) octyl-agarose. Another two-step procedure: (a) concanavalin A-agarose, (b) L-tryptophan-agarose, gives about 10,000-fold purification. The overall recovery of interferon in both cases in close to 90%.     

Isolation and characterization of two oncofetal glycoproteins from hamster pancreas using concanavalin A and preparative electrophoresis

Pancreatic fetal acinar antigens in the Syrian golden hamster, which are associated with development of the pancreas, have been previously described. In this study, two major antigens were isolated from fetal pancreas using affinity chromatography on Con A-Sepharose and preparative electrophoresis. Homogenates from fetal and adult pancreas were analyzed for their ability to bind to concanavalin A. This lectin allowed obtention of eluted fractions accounting for 2 and 0.7%, respectively, of the protein content in crude extracts. Concanavalin A-positive fraction from fetal pancreas contained two major carbohydrate-reactive glycoproteins of relative molecular weight (Mr) 80 000 and 58 000 in SDS-polyacrylamide gel electrophoresis. Both behaved as fetal antigens in nitrocellulose blot immunoassay. Similar experiments with chemically induced tumors of the pancreas led to a concanavalin A fraction containing the 80 and 58 kDa fetal glycoproteins; but in this case, the fraction was quite heterogeneous. Our data provide new support for the existence of differentiation antigens in the acinar cells of the pancreas, and indicate that two major ones are glycoproteins. Moreover, both are expressed in pancreatic tumors.     

Zein of maize grain: I — isolation by gel filtration and characterization of monomeric and dimeric species

Unreduced zein chromatographed on Sephadex G 200 in 8 M urea, on G 100 in 1.5 or 2.5% sodium dodecyl sulfate (SDS) and on hydroxypropylated G 100 in 70% ethanol was resolved into two minor fractions A and B and two major ones D and M irrespective of the medium. The quantitative importance of the fraction M was dependent on the isolation conditions of zein. It decreased from 53% of the proteins contained in ethanolic extract and chromatographed as they were extracted, to 40% of the purified zein. The molecular weight values obtained from SDS-polyacrylamide gel electrophoresis and amino acid compositional data indicated that fractions D and M, as isolated from purified zein in the presence of ethanol, represented respectively dimeric and monomeric forms of a mixture of M_r 22 000 and 24 000 polypeptides with threonine or phenylalanine as NH₂-terminal residue.Electrophoretic analysis of selectively carbamylated fraction M on starch gel at pH 3.5 revealed that zein subunits comprised several polypeptides differing in the number and the nature of basic amino acids. At least one of these polypeptides contained one lysyl residue.     

Isolation and characterization of human placenta fibronectin

Fibronectin was isolated from human placenta tissues and compared with human plasma fibronectin. Placenta and plasma fibronectins had similar amino acid compositions, immunological properties, and cell attachment-promoting activities, but differed in apparent molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, which could be accounted for at least partly by the difference in carbohydrate composition. Unlike plasma fibronectin, placenta fibronectin failed to form a precipitin line with concanavalin A in a double diffusion system. The non- or low-reactivity of placenta fibronectin with this lectin was also demonstrated by affinity chromatography with concanavalin A-agarose, in which more than 90% of the radiolabeled glycopeptides derived from placenta fibronectin was not retained on the gel. The two fibronectins also differed in the reactivity with Lens culinaris agglutinin of their glycopeptide fractions. These data indicate that placenta and plasma fibronectins are different in their carbohydrate structures and, therefore, suggest the presence of a tissue- or cell-specific mechanism for processing the carbohydrates of this glycoprotein.     

Partial purification and characterization of a neutral protease which cleaves the N-terminal propeptides from procollagen

A rapid assay procedure was developed for cleavage of the N-terminal propeptides of procollagen. With the assay a neutral procollagen N-protease was purified about 300-fold from chick embryo tendon extract. The enzyme had an apparent molecular weight of 260 000 and a pH optimum of 7.4. Ca2+ was required for enzymic activity but this requirement was partially replaced by Mg2+ or Mn2+. The enzyme was bound to concanavalin A-agarose and therefore was presumably a glycoprotein. The N-propeptides released from type I procollagen were of about 23 000 and 11 000 daltons as estimated by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The partially purified enzyme was also found to cleave type II procollagen and the N-propeptide obtained was about 18 000 daltons. Heat denaturation of either type I or type II procollagen decreased the rate at which the proteins were cleaved by the N-protease.     

Chemical characterization of recombinant human leukocyte interferon A using fast atom bombardment mass spectrometry

Proteolytic digests of biologically active fractions of recombinant human leukocyte interferon A expressed in large quantities in Escherichia coli were analyzed by fast atom bombardment mass spectrometry and high-performance liquid chromatography. The values observed in the mass spectra of digests of the major fraction of recombinant human leukocyte interferon A with trypsin and Staphylococcus aureus protease V8 accounted for 93% of the amino acid sequences of human leukocyte interferon A predicted from the nucleotide sequence of the gene encoding the protein, indicating that the major fraction of recombinant human leukocyte interferon A was expressed with the same amino acid sequence as that translated from the nucleotide sequence of the gene encoding the protein. Mass spectrometry of proteolytic digests of two minor fractions of recombinant human leukocyte interferon A and mass and amino acid analyses of their high-performance liquid chromatography fractions showed that the amino group of the N-terminal amino acid residue of interferon was in part acetylated, and the Cys-1 and Cys-98 residues were oxidized to cysteic acid or linked to glutathione. These findings suggest that amino acid residues in recombinant proteins prepared in large quantities in E. coli are modified post-translationally.     

Physico-Chemical Characterization of Hamster Interferon

The glycoprotein nature of Syrian hamster interferon was tested on several immobilized lectins. The specific retention of small portion (20%) of interferon activity was observed only on concanavalin A-agarose; Component I of the interferon (not retained) has an apparent molecular weight of 23,500 whereas Component II (retained) is larger, 31,500. The apparent hydrophobicity of Syrian hamster interferon was probed by its chromatography on: (a) straight chain hydrocarbons of varied length; (b) aromatic ligands (aminobenzene, benzylamine, β-phenylethylamine, γ-phenyl-propylamine); ligands listed in (a) and (b) were immobilized to cyanogen bromide-activated agarose (isoure linkage); and (c) phenyl-agarose (Phenyl-Sepharose CL-4B), an aromatic ligand immobilized vi 2-hydroxypropyl arm to the agarose (ether linkage).

For a hydrophobic interaction to occur under physiological solvent conditions, the hydrocarbon arm (isourea 1inkage) must be C₉ to C₁₀ carbon atoms long, whereas the aromatic ligand (isourea linkage) must be removed from the agarose matrix by a molecular arm of C₃ carbon atoms. There is no significant binding of hamster interferon to phenyl-agarose (ether linkage) near neutral pH.

The apparent hydrophobicity of Syrian hamster interferon can be profoundly influenced by the pH of the solvent. At lower pH values, interferon binds to both octyl-agarose and phenyl-agarose. The midpoint of transition between binding of interferon and its release from these ligands is about the same, pH 6.0, suggesting the identity of the binding site on the interferon molecule for both aliphatic and aromatic hydrocarbons.     

Purification and partial characterization of plasminogen activator from human uterine tissue.

A procedure was developed for the purification of a plasminogen activator from human uterine tissue. It involves six consecutive steps: (1) extraction of the plasminogen activator from delipidated uterine tissue with 0.3 M potassium acetate buffer, pH 4.2; (2) ammonium sulphate precipitation; (3) zinc chelate-agarose chromatography; (4) n-butyl-agarose chromatography; (5) concanavalin A-agarose chromatography; and (6) gel filtration on Sephadex G-150. The specific activity of the final plasminogen activator preparation was increased by a factor 4500 as compared with the crude extract. The purified plasminogen activator showed a strong tendency to adsorb to surfaces. This could be effectively prevented by Tween-80. The molecular weight of the plasminogen activator was 64 000 as estimated by gel filtration in 1.0 M NaCl and 69 000 as estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The plasminogen activator consisted of two chains (molecular weights 31 000 and 38 000) connected by disulphide bridges. The smallest chain contained the serine residue of the active site as deduced from the incorporation of the tritium label of [3H]diisopropylphosphofluoridate.