A monoclonal antibody against human urokinase: the epitope structure and sequence homology with a human tissue-type plasminogen activator

Our previous study showed that an epitope defined by a monoclonal antibody against human urokinase is located on the 33-Kdalton catalytic domain of the enzyme (Nakamura, M. et al., Cell Struct Funct., 9, 167-179, 1984). The epitope structure was further determined and characterized on one-dimensional SDS-polyacrylamide slab gel maps of CNBr-cleaved polypeptide fragments as well as on their Western blots. A single homogeneous polypeptide with an approximate molecular weight of 3.4-Kdaltons was found to be antigenic. The monoclonal antibody exhibited a stronger inhibition of the enzyme activity than the polyclonal antibodies tested, and cross-reacted with a 65-Kdalton tissue-type plasminogen activator present in Detroit 562 cells. From these results and data made up with the help of a computer comparison of known sequences of urokinase and a tissue-type plasminogen activator, we concluded that the epitope is Cys-Gln-Gly-Asp-Ser-Gly-Gly-Pro-Leu-Val-Cys and contains a catalytically active residue, serine.     

One-step immunopurification and lectinochemical characterization of the Duffy atypical chemokine receptor from human erythrocytes

Duffy antigen/receptor for chemokines (DARC) is a glycosylated seven-transmembrane protein acting as a blood group antigen, a chemokine binding protein and a receptor for Plasmodium vivax malaria parasite. It is present on erythrocytes and endothelial cells of postcapillary venules. The N-terminal extracellular domain of the Duffy glycoprotein carries Fy(a)/Fy(b) blood group antigens and Fy6 linear epitope recognized by monoclonal antibodies. Previously, we have shown that recombinant Duffy protein expressed in K562 cells has three N-linked oligosaccharide chains, which are mainly of complex-type. Here we report a one-step purification method of Duffy protein from human erythrocytes. DARC was extracted from erythrocyte membranes in the presence of 1% n-dodecyl-β-D-maltoside (DDM) and 0.05% cholesteryl hemisuccinate (CHS) and purified by affinity chromatography using immobilized anti-Fy6 2C3 mouse monoclonal antibody. Duffy glycoprotein was eluted from the column with synthetic DFEDVWN peptide containing epitope for 2C3 monoclonal antibody. In this single-step immunoaffinity purification method we obtained highly purified DARC, which migrates in SDS-polyacrylamide gel as a major diffuse band corresponding to a molecular mass of 40-47?kDa. In ELISA purified Duffy glycoprotein binds anti-Duffy antibodies recognizing epitopes located on distinct regions of the molecule. Results of circular dichroism measurement indicate that purified DARC has a high content of α-helical secondary structure typical for chemokine receptors. Analysis of DARC glycans performed by means of lectin blotting and glycosidase digestion suggests that native Duffy N-glycans are mostly triantennary complex-type, terminated with α2-3- and α2-6-linked sialic acid residues with bisecting GlcNAc and α1-6-linked fucose at the core.     

增殖细胞核抗原蛋白在Spodoptera frugiperda昆虫细胞中的表达及纯化

目的:利用昆虫细胞表达系统生产重组的人增殖细胞核抗原(proliferating cell nuclear antigen,PCNA),并进行纯化和抗体结合特性鉴定。方法:以HeLa细胞逆转录的cDNA为模板,扩增人PCNA基因,并插入杆状病毒载体AcMNPV。利用昆虫细胞得到PCNA基因的重组杆状病毒。病毒感染细胞表达蛋白,联合镍柱亲和层析和离子交换层析获得高纯度的重组人PCNA蛋白。ELISA法测定抗体结合特异性。结果:以HeLa细胞cDNA为模板得到的基因序列同GenBank的人PCNA基因序列一致。草地贪夜蛾细胞(Spodoptera frugiperda,Sf9)表达重组人PCNA(recombinant human PCNA,rPCNA)的最佳感染值(MOI)和感染时间分别为0.05h和144h。rPCNA的产量高达110mg/L细胞,纯度95%。间接ELISA法检测抗体结合特性,rPCNA的敏感性和特异性分别为93.3%和85.0%。结论:建立了rPCNA的表达和纯化方法,获得了高效表达、高度抗体结合特异性的PCNA蛋白,该蛋白质能进一步开发为PCNA相关疾病的体外诊断试剂盒,具较大的应用价值。     

Identification, immunoaffinity purification and partial characterization of a human decidua-associated protein

A crude extract of pooled early-pregnancy decidual tissue was enriched for soluble decidual proteins by exhaustive affinity absorption with antibodies to human serum proteins immobilized on Eupergit C. The partly purified extract was used to prepare monoclonal antibodies. A monoclonal antibody was obtained recognizing an antigen present in extract of decidual tissue and not in extract of proliferative endometrium. The monoclonal antibody was used for immunoaffinity purification of the decidua-associated protein. By SDS-PAGE analysis, under reducing conditions it yielded 2 bands at apparent molecular weights of 55,000 and 25,000. Under non-reducing conditions a single protein band at apparent molecular weight of 200,000 was observed. The Mr 200,000 protein was named hDP200 and the Mr 55,000 protein was named hDP55. It is suggested that hDP55 is a subunit of the hDP200. The hDP200 did not react with polyclonal antibodies specific for PP12 and PP14. PP14 has been shown to be immunologically indistinguishable from PEP and alpha 2-PEG. Our data therefore suggest that hDP200 is a novel human decidua-associated protein.     

血管内皮生长因子全长抗体在毕赤酵母中的表达与活性鉴定

目的:构建血管内皮生长因子(VEGF)全长抗体表达载体pPICZαA-VH-CH-VL-CL,评价其在毕赤酵母中的表达产物与抗原的结合特性,及其抑制细胞增殖的活性。方法:利用基因合成分别获得VEGF抗体CL和CH序列,分别构建pPICZαA-CH和pPICZαA-CL重组质粒,再利用同尾酶特性构建双启动子表达盒的重组pPICZαA-CH-CL载体,用Westen印迹对其进行表达鉴定后将VH和VL序列插入该载体,获得VEGF的全长抗体表达载体pPICZαA-VH-CH-VL-CL;通过膜筛和ELISA进行菌株筛选,并对VEGF抗体表达阳性菌株进行小量表达和纯化,采用CCK-8法对其抑制人脐静脉内皮细胞(HUVEC)增殖的活性进行初步评价。结果:获得表达轻、重链的VEGF抗体表达载体,ELISA实验证明pPICZαA-VH-CH-VL-CL具有一定的VEGF抗原结合特性;体外增殖实验表明,该抗体可以以剂量依赖性抑制HUVEC增殖。结论:在毕赤酵母中表达、纯化了具有一定功能活性的VEGF全长抗体,为后续比较研究酵母糖基化改造对VEGF抗体的药效学和药代学的影响提供了基础。     

Human tumor necrosis factor-alpha receptor. Purification by immunoaffinity chromatography and initial characterization

The receptor for human tumor necrosis factor-alpha (TNF-alpha) was isolated from a subclone of the human histiocytic lymphoma cell line U937. These cells exhibit a single class of high affinity receptors (Kd = 0.51 +/- 0.25 nM) with an average density of 55,000 +/- 5,000 binding sites/cell. After solubilization with detergent, the receptor retained its ability to bind free TNF-alpha but failed to bind to TNF-alpha immobilized on various solid supports. For receptor purification, 125I-TNF-alpha was covalently attached to the receptor on intact cells by the bifunctional cross-linking reagents ethylene glycolbis(succinimidylsuccinate) or 3,3-dithiobis(sulfosuccinimidylpropionate). The cells were then solubilized with the nonionic detergent Triton X-100, and the supernatants, clarified by centrifugation, were passed over an IgG-Sepharose column prepared from TNF-alpha antiserum. The receptor-rich fraction from the antibody column was further purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These two steps together provided approximately 165,000-fold purification of the TNF-alpha receptor. The TNF-alpha receptor-ligand complex obtained by this method had a subunit molecular weight of 100,000 +/- 5,000 when examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis but on gel filtration the complex migrated with an apparent molecular weight of 480,000 +/- 32,000. However, the receptor showed a molecular weight of 65,000 +/- 32,000 when gel filtration was performed in the absence of ligand. Additional characteristics of the receptor are discussed.     

A novel TNFalpha antagonizing peptide-Fc fusion protein designed based on CDRs of TNFalpha neutralizing monoclonal antibody

The variable regions of antibody molecules bind antigens with high affinity and specificity. The binding sites are imparted largely to the hypervariable portions (i.e., CDRs) of the variable region. Peptides derived from CDRs can bind antigen with similar specificity acting as mimic of antibody and become drug-designing core, although with markedly lower affinity. In order to increase the affinity and bioactivity, in this study, a novel peptide (PT) designed on CDRs of a TNFalpha neutralizing monoclonal antibody Z12 was linked with Fc fragment of human IgG1. The interaction mode of PT-linker-Fc (PLF) with TNFalpha was analyzed with computer-guided molecular modeling method. After expression in Escherichia coli and purification, recombinant PT-linker-Fc could bind directly with the TNFalpha coated on the ELISA plates. Furthermore, PLF could competitively inhibit the binding of Z12 to TNFalpha and also inhibit the TNFalpha-induced cytotoxicity on L929 cells. The TNFalpha antagonizing activity of PLF was significantly higher than that of the free peptide. This study highlights the potential of human Fc to enhance the potency of peptides designed on the CDRs of antibodies and could be useful in developing new TNFalpha antagonists.     

Two satisfactory methods for purification of human acrosin

Acrosin has been purified from human sperm cells by two alternative procedures which give purer products and in higher yields than could be achieved previously. The products were characterized by their molecular weight, catalytic action, sensitivity to inhibitors, and reaction with a polyclonal anti-acrosin antibody. After acid extraction of the cells, one method involves removal of acrosin inhibitors by vacuum dialysis, followed by affinity chromatography on a soybean trypsin inhibitor (SBTI) column, and therefore requires that the acrosin be in an active form capable of binding to the inhibitor. The other method involves affinity chromatography on a column of a monoclonal anti-acrosin antibody (MAb) and can be used to provide either active or proenzyme forms of acrosin, by choice of extraction conditions and inclusion of appropriate inhibitors. The yield of human acrosin from the SBTI method was 104% and from the MAb column was 75%. It is hoped that these procedures will make the very scarce human acrosin more readily available for further study.     

Purification and characterization of a chimeric bifunctional antibody specific for human carcinoembryonic antigen and indium-benzyl-EDTA

We describe the purification and characterization of a genetically engineered mouse/human chimeric bifunctional antibody specific for human carcinoembryonic antigen and indium-benzyl-EDTA. A clone expressing the bifunctional antibody has been previously described by our group and was found in this investigation also to express monospecific antibodies as well as Ig forms with mismatched light and heavy chains. The physicochemical properties of these various chimeric immunoglobulins were nearly identical. Isoelectric focusing showed that all these immunoglobulins have pI values between 8.47 and 8.80. A purification method that separates the bifunctional antibody from other Ig forms expressed in the same clone has been devised by relying on a unique interaction between the metal chelate binding region of these antibodies and the sulfopropyl functional group of a TSK SP 5-PW column.     

Synergistic action of monoclonal antibodies directed at p55 and p75 chains of the human IL-2-receptor

TU27, a mouse IgG1 mAb directed at the p75 chain of the human IL-2R, was analyzed for its ability to interact with IL-2 binding on isolated p75 chains (YT-2C2 cells) and high affinity p55/p75 receptors (human alloreactive T cell clone 4AS), to inhibit IL-2-induced proliferation (4AS cells) and to cooperate with an anti-p55 chain mAb (33B3.1) for inhibiting IL-2 binding and proliferation. TU27 and IL-2 bound to the isolated p75 chain expressed by YT-2C2 cells with respective dissociation constants (Kd) of 1.3 and 1 nM. They cross-inhibited each other for binding with inhibition constants (Ki) in agreement with their respective Kd values. The nature of the interaction was, however, not purely competitive and suggested nonidentical epitopes for the two ligands on the p75 chain. On 4AS cells, IL-2 bound with high affinity (Kd = 50 pM) and TU27 with an affinity similar to that found on YT-2C2 cells. The binding of TU27 and IL-2 were also mutually exclusive on 4AS cells. However, the mechanism of interaction of TU27 with IL-2 was complex since the inhibitory potency of the antibody depended on temperature, antibody preincubation and time of assay. Data obtained at 4 degrees C in the presence of suboptimal, tracer-like concentrations of IL-2 indicated that the intrinsic affinity of TU27 for the high affinity configuration was 15-fold lower than for the isolated p75 chain and argued in favor of the affinity-conversion model (as opposed to the preformed complex model) in which p55 and p75 are dissociated in the absence of IL-2. At 37 degrees C, TU27 inhibited IL-2 binding only on short time assays (6 min). Longer time (30 min) of IL-2 binding resulted in an almost complete disappearance of the effect of TU27, suggesting that internalization of the high affinity p55/p75/IL2 complex enables the cells to escape from the inhibitory effect of TU27. In the presence of the 33B3.1 mAb, the interaction of TU27 with IL-2 resembled the one observed on YT-2C2 cells, suggesting that 33B3.1 is able to inhibit the IL-2-induced association of p55 and p75. Both antibody were found to synergize on 4AS cells, as a result of a cooperative mechanism in which 33B3.1 blocks the formation of the high affinity complex hence allowing TU27 to bind with higher affinity, and TU27 blocks IL-2 binding to the p75 chain. Proliferation studies corroborated the binding experiments.(ABSTRACT TRUNCATED AT 400 WORDS)     

A purification of microsomal glucose-6-phosphatase from human tissue

Glucose-6-phosphatase, an enzyme of the microsomal fraction, is a major intermediate in the mobilization of glucose from liver cells. Lack of a purified preparation of this enzyme has hampered efforts to understand the molecular details of Glycogen Storage Disease Type Ia (von Gierke's disease). The present study was undertaken to purify this membrane-bound enzyme from human placenta and liver using Sepharose affinity chromatography with glucose-6-phosphate as the bound ligand. Of the two tissues tested, the placenta gave the better results, perhaps because the purification began with fresh tissue. Protein eluting from the affinity column for a placental preparation gave three peaks of specific activity representing 45-, 33-, and 600-fold purification with a yield of about 2%. Specific activity determined for liver tissue was far more variable and represented a purification of about 5-fold. SDS-PAGE of protein from both tissues indicated only three bands in the range of 58–64,000 molecular weight. Although not purified to homogeneity, the scheme reported here represents a significant advance in the purification of functional G6Pase from human sources.     

High-performance liquid chromatography of proteins on deformed nonporous agarose beads: immuno-affinity chromatography, exemplified with human growth hormone as ligand and a combination of ethylene glycol and salt for desorption of the antibodies

An affinity chromatography column packed with nonporous agarose beads derivatized with human growth hormone via carbonyldiimidazol was used for the purification of antibodies against human growth hormone from antiserum. Desorption with 1 M sodium chloride in 60% ethylene glycol at pH 9.8 gave 100% total recovery of the antibodies, as measured by radioimmunoassay. The adsorption/desorption process is discussed in terms of hydrophobic and electrostatic interaction (these interactions may be involved in the bond between antibody and antigen in a cooperative fashion). The binding capacity of the column was estimated at about 50 micrograms of antibodies per gram sedimented agarose beads.     

Rapid Purification of a New Humanized Single-chain Fv Antibody／Human Interleukin-2 Fusion Protein Reactive against HER2 Receptor

Overexpression of the proto-oncogene c-erbB-2, neuor HER2 has been shown in many human tumor cells,especially in breast cancer cells [1–5], which is thought tobe important in human carcinogenesis. c-erbB-2 geneencodes a 185 kD transmembrane glycoprotein …     

抗P-选择蛋白人源性单克隆抗体的制备

目的:获得人源性抗P-选择蛋白(selectin)特异性抗体,为相关疾病治疗奠定基础。方法:在HEK293细胞中真核分泌表达人P-选择蛋白功能性片段,以此蛋白片段作为抗原,利用本室构建的大容量全合成人源性噬菌体抗体库进行筛选,经过3轮固相筛选后,阳性克隆得到富集;将其中富集效果最好的一株单链抗体A1改造成全抗体(IgG1),重组质粒转染H293细胞后,抗体得到表达;表达后在全抗体水平上用ELISA和Western印迹分别验证了A1抗体的特异性,并通过非竞争ELISA方法初步测定这株抗体的亲和力。结果:3轮筛选得到3株特异性噬菌体抗体,其中富集效果最好的单链抗体A1改造成全抗体形式后特异性良好,抗体亲和力Kd=2×10-8 mol/L。结论:筛选得到一株特异性较好的抗P-选择蛋白人源性单克隆抗体A1,其特异性和亲和力较好,有继续开发的价值。     

A combination of cation exchange and ligand-affinity chromatography for purification of two molecular species of the folate binding protein in human milk,one equipped with a hydrophobic glycosyl phosphatidylinositol tail: characterization of hydrophobicity and electrical charge

Cation exchange chromatography combined with ligand (methotrexate) affinity chromatography on a column desorbed with a pH-gradient was used for separation and large scale purification of two folate binding proteins in human milk. One of the proteins, which had a molecular size of 27 kDa on gel filtration and eluted from the affinity column at pH 5-6 was a cleavage product of a 100 kDa protein eluted at pH 3-4 as evidenced by identical N-terminal amino acid sequences and a reduction in the molecular size of the latter protein to 27 kDa after cleavage of its hydrophobic glycosylphosphatidyl-inositol tail that inserts into Triton X-100 micelles. Chromatofocusing showed that both proteins possessed multiple isoelectric points within the pH range 7-9. The 100 kDa protein exhibited a high affinity to hydrophobic interaction chromatographic gels, whereas this was only the case with unliganded forms of the 27 kDa protein indicative of a decrease in the hydrophobicity of the protein after ligand binding.     

Characterization of the human IL-5 receptors on eosinophils

Interleukin 5 (IL-5) receptors on the cell surface of human eosinophils and other hematopoietic cells were characterized using radiolabeled recombinant IL-5. The binding of 35S-labeled murine IL-5 to eosinophils from normal human peripheral blood was rapid and saturable within a 30-min incubation at both 4 and 37 degrees C. The binding of 35S-labeled murine IL-5 to eosinophils was inhibited by an excess of unlabeled murine and human IL-5 or by an anti-murine IL-5 monoclonal antibody (NC17) but not by other human cytokines. Scatchard plot analysis revealed that human eosinophils have a single class of high affinity receptor (Kd 170-330 pM; number of binding sites: 260-380/cell). IL-5 receptors on eosinophils from four patients with eosinophilia displayed similar characteristics. Affinity cross-linking experiments resulted in the identification of human IL-5 receptor on eosinophils with a molecular mass of 55-60 kDa. Among the various cells besides eosinophils and cell lines that we could test, a subline of HL-60 (YY-1 cells) was found to display a significant number of IL-5 receptor. These results suggest that IL-5 may act on limited types of cells in the human system.     

Purification of a 130-kDa T cell glycoprotein that binds human interleukin 4 with high affinity

The interleukin 4 (IL-4) receptor was purified from the gibbon T cell line MLA 144. These cells were found to express high numbers of human IL-4-binding proteins (5000-6000 sites/cell) with an affinity constant (Kd) similar to that measured in human cell lines (Kd = 40-70 pM). Affinity cross-linking of 125I-IL-4 to human cell lines and MLA 144 cells demonstrated the labeling of three proteins of approximately 130, 75, and 65 kDa. Human IL-4-binding sites were solubilized from MLA 144 cells using Triton X-100 and then purified by carboxymethyl chromatography, which removed 50% of the protein without loss of IL-4-binding activity. Then sequential affinity purification over wheat germ agglutinin and a single IL-4 Affi-Gel 10 column resulted in a final 8000-fold purification of the IL-4 receptor. When analyzed on a silver-stained sodium dodecyl sulfate-polyacrylamide gel, the purified receptor migrated as a single molecular species of 130 +/- 5 kDa. Identification of the 130-kDa protein as the IL-4 receptor was demonstrated by cross-linking experiments and specific binding of 125I-IL-4 to nitrocellulose membranes after electrophoretic transfer of the purified receptor on sodium dodecyl sulfate-polyacrylamide gel.     

人源抗狂犬病毒中和性全抗体在昆虫细胞中的表达

将来源于噬菌体抗体库的人源狂犬病毒糖蛋白特异性单抗G10Fab的基因 ,克隆入杆状病毒人源IgG抗体表达载体 ,通过转染将重组质粒导入昆虫细胞 ,以全抗体的形式表达了一株人源抗狂犬病毒基因工程抗体G10。用亲和层析的方法纯化了表达产物 ,经与一株鼠源糖蛋白特异性单抗竞争证实 ,该单克隆抗体特异性识别狂犬病毒糖蛋白 ,亲和力约为 10 -9M。体外中和实验证明 ,该单抗对狂犬病毒aG株具有体外中和活性     

Partial purification of the 5-hydroxytryptamine-reuptake system from human blood platelets using a citalopram-derived affinity resin [corrected

This paper describes a procedure for the synthesis and application of a citalopram-derived affinity resin in purifying the 5HT-reuptake system from human blood platelets. A two-step scheme has been developed for partial purification, based on wheat germ agglutinin-lectin (WGA) affinity and citalopram affinity chromatographies. Upon solubilization of the carrier with 1% digitonin, a 50-70-fold increase in specific [3H]imipramine binding activity with a 70% recovery could be accomplished through WGA-lectin chromatography. The WGA pool was then subjected to affinity chromatography on citalopram-agarose. At least 90% of the binding capacity adsorbed to the column. Specific elution using 10 microM citalopram resulted in a 22% recovery of binding activity. A 10,000-fold overall purification was obtained by using this two-step procedure. Analysis of the fractions on SDS-PAGE after 125I labeling revealed specific elution of 78- and 55-kDa proteins concomitant with the appearance of [3H]imipramine binding activity. The pharmacological profile of the partially purified reuptake system correlated well with that derived from the crude membrane-bound reuptake system, suggesting a copurification of the 5HT binding activity and [3H]imipramine binding activity.     

Identification and immunohistochemical localization of a tryptophan binding protein in nuclear envelopes of rat liver

A tryptophan binding protein which was identified by binding studies has been purified to apparent homogeneity from rat liver nuclear envelopes. Two affinity matrices, namely, concanavalin A-agarose and tryptophan-agarose, were utilized for purification of the binding protein. Findings with lectin affinity chromatography suggested that the binding entity was a glycoprotein since it could be eluted off the column with methyl alpha-D-mannopyranoside (0.2 M). Eluates from both columns, when electrophoresed separately (under denaturing conditions) on polyacrylamide gels, revealed the presence of a protein with an apparent molecular weight of approximately 33,000-34,000 which is the same as that observed when covalently bound (i.e., crosslinked) [3H]-tryptophan is analyzed on polyacrylamide gels under denaturing conditions and then autoradiographed. Polyclonal antibodies raised against the binding protein recognized polypeptides with molecular weights of 64,000 and 33,000-34,000 when analyzed by the Western blot technique, suggesting that the protein was probably a dimer. Immunohistochemical studies revealed that the antigen is localized in the nuclear membranes, thereby corroborating our biochemical premise that the binding protein was present in the nuclear envelopes.