Purification and characterization of recombinant human pro-urokinase produced in silkworm using a baculovirus vector

Summary A recombinant baculovirus (BmNPV-pk2) was constructed by inserting the human pro-urokinase(pro-UK) cDNA into the genome of baculovirus Bombyx mori nuclear polyhedrosis virus (BmNPV) adjacent to the strong polyhedrin promoter. The recombinant virus replicated in silkworm larvae, which synthesized 30g pro-UK/ml in the haemolymph within 4 days post-infection. Purification to near homogeneity was accomplished by fractional precipitation with ammonium sulphate and immunoaffinity chromatography with an overall yield of 23% and a specific activity of 100,000IU/mg in fibrin plate assay. This purified product was comprised of a single chain protein with approximately Mr. 50kDa as determined by SDS-PAGE gel. The N-Terminal amino acids sequence revealed that the secretion signal of pro-UK was correctly processed.     

重组人尿激酶原在CHO细胞中的高效表达及其纯化

用鸡β- globin的MAR序列和人看家基因延伸因子1α(hEF-1α)的调控序列以及旱獭RNA稳定与输出序列,构建了重组人尿激酶原(recombinant human pro-urokinase,rhPro - UK)的高效表达载体,在CHO细胞中获得了rhPro - UK的高效稳定表达,rhPro - UK的表达水平达到1299 IU(以百万细胞1d的表达量计).采用阳离子交换层析、疏水层析和凝胶排阻层析的三步工艺纯化表达rhPro - UK的CHO细胞培养上清液,rhPro - UK的纯度达到98％、回收率为60％ ～70％.     

Carbohydrate linkage site in the beta-chain of human fibrin.

The beta-chain of fibrin was cleaved with trypsin or cyanogen bromide. Carbohydrate containing fragments were isolated by affinity chromatography on concanavalin A-agarose. The fragments were analysed for amino acid sequence and for amino and carbohydrate composition. The sequence of 21 amino acid residues around the carbohydrate attachment point was determined. The carbohydrate carrying amino acid was identified as aspartic acid/asparagine.     

Optimization of pro-urokinase secretion from recombinant Saccharomyces cerevisiae

Secretion of a nonglycosylated form of human pro-urokinase, also known as single-chain urinary plasminogen activator (scu-PA), from Saccharomyces cerevisiae is described. A "supersecreting" yeast strain harboring multiple copies of integrated plasmids was grown batchwise and at constant respiratory quotient (RQ) in 20-L fermenters. Because the promoters used to drive expression of the pro-urokinase genes are not tightly regulated, secretion into the culture supernatant was growth associated. Although the final cell density achieved in the perturbed-batch fermentation (45 g dry wt/L) was less than that observed in the RQ-controlled culture (77 g dry wt/L), the scu-PA titer in the perturbed-batch fermentation (1863 IU/mL) was nearly twice that attained at constant RQ (1108 IU/mL). The effects on cell growth and scu-PA titer of other process variables (pH, temperature, phosphate concentration, and medium composition) are also discussed.     

Distribution of recombinant pro-urokinase in the rabbit blocked carotid artery

Distribution of recombinant pro-urokinase (PRU) in segments of blocked carotid arteries of rabbits was measured in 10, 20 and 30 minutes after i.v. administration of the RPU. Concentration of the latter in the bloodstream taken as 100% on the 3rd minute, after the infusion decreased to 42% in 10 min., 24% in 20 min., and 13% in 30 min. The RPU concentration decreased to 2% at the artery clamp point, to 20% at 10-15 cm from the clamp point, and remained constant for 10-30 min. A thrombolytic agent accumulated at the dead-end of the blocked artery, was not subject to rapid clearance in contrast to circulating pro-urokinase.     

Carbohydrate composition of human placental N-acetylhexosaminidase A and B.

The carbohydrate composition of N-acetyl-beta-D-hexosaminidases (EC 3.2.1.52) A, B and heat-converted B was determined by g.l.c. Similar quantities of mannose, N-acetyl-glucosamine and galactose are present in the A and B isoenzymes, whereas N-acetyl-neuraminic acid is found in significant amount in only the A isoenzyme. The heat-converted hexosaminidase B also contains only trace amounts of N-acetylneuraminic acid, but is about 1.5-fold richer in mannose and N-acetylglucosamine and nearly 2-fold richer in galactose than native hexosaminidase B. Since native and converted hexosaminidase B are thought to be composed of four identical protein chains, our results suggest that there may be variable glycosylation of these chains.     

Carbohydrate specificity of chicken and human tandem-repeat-type galectins-8 in composition of cells

The network of adhesion/growth-regulatory galectins in chicken (chicken galectin, CG) has only one tandemrepeat-type protein, CG8. Using a cell-based assay and probing galectin reactivity with a panel of fluorescent neoglycoconjugates (glycoprobes), its glycan-binding profile was determined. For internal validation, human galectin-8 (HG8) was tested. In comparison to HG8, CG8 showed a rather similar specificity: both galectins displayed high affinity to blood group ABH antigens as well as to 3′-sialylated and 3′-sulfated lactosamine chains. The most remarkable difference was found to be an ability of HG8 (but not CG8) to bind the disaccharide Galβ1-3GlcNAc (Le^c) as well as branched and linear oligolactosamines. The glycan-binding profile was shown to be influenced by glycocalix of the cell, where the galectin is anchored. Particularly, glycosidase treatment of galectin-loaded cells led to the change of the profile. Thus, we suppose the involvement of cis-glycans in the interaction of cell-anchored galectins with external glycoconjugates.     

Carbohydrate composition of normal and variant human alpha 1-protease inhibitors.

Carbohydrate composition of normal human alpha 1-protease inhibitor (PiM₁) and several variant inhibitors (PiM₂, PiM₃, PiA, PiS, and PiZ) was determined by methanolysis of the samples followed by quantitative analysis of both neutral and amino sugars using gas-liquid chromatography. All normal and variant inhibitors contained nine mannose, seven galactose, ten N-acetylglucosamine, and eight N-acetylneuraminic acid residues per molecule, and no significant difference was found in their carbohydrate compositions. PiA is a variant with the fastest anodal electrophoretic mobility, and PiZ is a variant with the slowest mobility thus far reported. The differences in electrophoretic mobility of these Pi variants are entirely due to their amino acid substitutions determined previously. These amino acid substitutions have no effect on the carbohydrate structure of the protease inhibitor.     

Carbohydrate binding specificity of the recombinant chitin-binding domain of human macrophage chitinase

The chitin-binding domain of human macrophage chitinase was expressed as a fusion protein with glutathione S-transferase in Escherichia coli and assayed for its binding activity. The purified recombinant chitin-binding domain bound to chitin, but not to glucan, xylan, or mannan. The binding of the recombinant chitin-binding domain to chitin was inhibited by N-acetylglucosamine, di-N-acetylchitobiose, and hyaluronan, but not by N-acetylgalactosamine or chondroitin. Furthermore, a solid-phase binding assay showed that the recombinant domain interacts specifically with hyaluronan and hybrid-type N-linked oligosaccharide chains on glycoproteins, and that the oligosaccharide-binding characteristics are similar to those of wheat germ agglutinin, a lectin that binds to chitin. The results suggest that human chitinase chitin-binding domain may be involved in tissue remodeling through binding to polysaccharides or extracellular matrix glycoproteins, and this recombinant protein can be used to elucidate biological functions of the enzyme.     

Carbohydrate structures of recombinant soluble human CD4 expressed in Chinese hamster ovary cells

Infection of T-lymphocytes and macrophages by human immunodeficiency virus (HIV) is mediated by the binding of the HIV envelope glycoprotein to the cell-surface receptor glycoprotein CD4. A soluble, recombinant CD4 molecule (rCD4), produced by expression of a truncated CD4 gene in Chinese hamster ovary (CHO) cells [Smith et al. (1987) Science 238, 1704-1707], is in clinical trials as a potential therapeutic agent in the treatment of acquired immunodeficiency syndrome (AIDS). In the present study, the structures of the Asn-linked oligosaccharides of soluble rCD4 have been elucidated. The rCD4 molecule has two potential sites for N-glycosylation, Asn-271 and Asn-300. Tryptic glycopeptides containing either of the sites were purified by reversed-phase HPLC, and their oligosaccharides were released enzymatically. The structures of the oligosaccharides were determined by methylation analysis, high-pH anion-exchange chromatography, fast-atom bombardment mass spectrometry, and 1H NMR spectroscopy at 500 MHz. Asn-271 was found to carry diantennary N-acetyllactosamine-type ("complex") oligosaccharides, of which 8% were asialo, 55% were monosialyl, and 37% were disialyl. Approximately 18% of these structures contained fucose alpha(1-->6) linked to the reducing GlcNAc residue. Two different hybrid structures were found to account for 34% of the oligosaccharides attached to Asn-300. The remainder of the oligosaccharides attached to Asn-300 were diantennary N-acetyllactosamine-type, of which 10% were asialo, 61% were monosialyl, and 29% were disialyl. Approximately 9% of the hybrid structures and 40% of the N-acetyllactosamine structures at Asn-300 were found to contain fucose alpha(1-->6) linked to the innermost GlcNAc residue.     

Carbohydrate structure of recombinant human uterine tissue plasminogen activator expressed in mouse epithelial cells

Recombinant human uterine tissue plasminogen activator (tPA), in part metabolically labeled with [6-3H]glucosamine or [35S]sulfate, was isolated from mouse epithelial cells (C127). Oligosaccharides present were liberated by treatment of tryptic glycopeptides with endo-beta-N-acetylglucosaminidase H or peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F and fractionated by high-performance liquid chromatography. The glycans were characterized by digestion with exoglycosidases, methylation analysis and, in part, by acetolysis and 1H-NMR spectroscopy. Glycopeptides comprising individual glycosylation sites were identified by N-terminal amino acid sequencing. The results demonstrate that recombinant tPA from C127 cells carries at Asn117 oligomannosidic glycans with 5-8 mannose residues as well as small amounts of hybrid-type species. Asn184 is only partially glycosylated and substituted by fucosylated triantennary and small amounts of diantennary N-acetyllactosaminic glycans. Likewise, Asn448 carries predominantly fucosylated triantennary species, in addition to, small amounts of diantennary and tetraantennary oligosaccharides. As a characteristic feature, part of the triantennary glycans at Asn184 and Asn448 contain additional Gal(alpha 1-3) substituents and/or sulfate groups linked to position six of beta-galactosyl residues forming NeuAc(alpha 2-3)[HO3S-6]Gal(beta 1-4) units. Oligosaccharides attached to Asn448 are almost completely substituted by (alpha 2-3)- or (alpha 2-6)-linked sialic acid residues and carry the majority of sulfate groups present. Glycans at Asn184 were found to be less sialylated and sulfated.     

Carbohydrate composition and taxonomy of the genusDipodascus

Carbohydrates released during acid hydrolysis of intact cells ofDipodascus were studied by gas-liquid chromatographic analysis as their trimethylsilyl derivatives. In addition, cells were characterized by pyrolysis gas-liquid chromatography and pyrolysis mass spectrometry. The data obtained support the classification ofDipodascus uninucleatus in a separate genusDipodascopsis. Glucuronic acid is present inD. uninucleatus and, therefore, a possible affinity to fungi classified in the Zygomycetes is considered.Dipodascus aggregatus andDipodascus australiensis were found to be rather different, but very close toGeotrichum candidum and related species.     

Stable production of recombinant pro-urokinase by human lymphoblastoid Namalwa KJM-1 cells: Host-cell dependency of the expressed-protein stability

Human pro-urokinase (pro-UK) gene was engineered for expression in mammalian cells. The stability of recombinant pro-UKs produced by two kinds of cells, Chinese hamster ovary (CHO) and human lymphoblastoid Namalwa KJM-1 cells, were compared. The pro-UK expressed in CHO cells in serum-free medium was degraded by cysteine endopeptidase secreted by CHO cells. This endopeptidase was inhibited by pchloromercuribenzonate (PCMB) and leupeptin more efficiently than by aprotinin. On the other hand, the pro-UK expressed in Namalwa KJM-1 cells was not degraded, resulting in the stable production of pro-UK at a rate of 2–3 g/10⁶ cells/day by use of a gene amplification method with dihydrofolate reductase (DHFR) in serum-free medium. Thus, Namalwa KJM-1 cells showed the desired characteristics as a host cell for the production of recombinant proteins. The stability of recombinant proteins produced in heterologous systems may vary depending on the host cells.Abbreviations ABTS 2,2-azino-di-(3-ethylbenzothiazoline) sulfonic acid diammonium salt - AMC 7-amino-4-methylcoumarin - CHO Chinese hamster ovary - DFP diisopropylfluorophosphate - DHFR dihydrofolate reductase - ELISA enzyme-linked immunosorbent assay - MCA 4-methylcoumaryl-7-amide - MTX methotrexate - NEAA non essential amino acid - NEM N-ethylmaleimide - PCMB p-chloromercuribenzonate - PMSF phenylmethanesulfonyl fluoride - pro-UK pro-urokinase     

Carbohydrate composition of bovine rhodopsin.

The carbohydrate content of bovine rhodopsin was investigated and found to be different from previously reported values. Rod outer segments were isolated from dark-adapted bovine retinas by sucrose flotation and purified by sucrose density contrifugation. Rhodopsin was extracted with detergents and purified by chromatographic procedures involving calcium phosphate/celite chromatography followed by affinity chromatograpy on concanavalin A-Sepharose (or in some cases, gel filtration on agarose). Purified preparations of rhodopsin had A278/A498 ratios of 1.6 to 2.0. After treatment of the rhodopsin with chloroform/methanol (2/1) to remove lipids and detergents, the carbohydrate content was measured by gas-liquid chromatography, colorimetric and enzymatic analyses, paper chromatography, and electrophoresis. Rhodopsin was found to have about 9 mol of mannose and 5 mol of glucosamine per mol of visual pigment. A molar ratio of mannose/glucosamine of about 2 was also found in samples of rhodopsin obtained from two other laboratories. The amino acid analysis was similar to previously published values.