A physicochemical study of protein G, a molecule with unique immunoglobulin G-binding properties

Protein G, an IgG-binding molecule, was prepared from the cell walls of a group G streptococcal strain, G-148. The protein could be extracted from the cells by papain digestion and purified by the sequential use of ion-exchange chromatography on DEAE-Sephadex, affinity chromatography on Sepharose-coupled human IgG, and gel chromatography on Sephadex G-200. Two protein bands with similar molecular weight, 34,000 and 36,000, were obtained when analyzing the pure protein G on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The yield using this purification scheme was 27% of the protein G solubilized from the cells or 70 micrograms/ml packed bacteria. The Stokes radius and frictional ratio of protein G were determined to 3.53 nm and 1.64, respectively, suggesting an elongated fibrous molecule. The protein did not contain any intrachain disulfide bonds. The amino acid composition of protein G was determined and was found to be different from that of protein A, the well known staphylococcal IgG-binding protein. The equilibrium constants of the reactions between protein G and human, rabbit, mouse, and goat polyclonal IgG, determined by Scatchard plots, ranged between 1 X 10(10) and 7 X 10(10), for rat polyclonal IgG 1.4 X 10(9), and human monoclonal IgG1, IgG2, IgG3, and IgG4 between 2 X 10(9) and 6 X 10(9). These affinity constants were always greater than the corresponding values for protein A. The binding between protein G and various polyclonal and monoclonal IgG was pH dependent between 2.8 and 10, strongest at pH 4 and 5, and weakest at pH 10.     

Isolation and characterization of a 14-kDa albumin-binding fragment of streptococcal protein G

Protein G, a streptococcal cell wall protein, has separate binding sites for human albumin and IgG. Streptococci expressing protein G were treated with the bacteriolytic agent mutanolysin. Several IgG- and human serum albumin (HSA)-binding peptides were identified in the material thus solubilized and one of these, a 14-kDa peptide, was found to bind HSA but not IgG in Western blot experiments. This molecule was purified by affinity chromatography on Sepharose coupled with HSA followed by gel filtration on Sepharose 6B and a final affinity chromatography on IgG-Sepharose, by which low Mr W(15 to 20 kDa)IgG-binding peptides were removed. In different binding experiments the purified 14-kDa peptide bound exclusively HSA and the equilibrium constant between the peptide and HSA was determined to be 3.4 X 10(8) M-1. The relation between the 14-kDa molecule and protein G was studied by analyzing the N-terminal amino acid sequence of the peptide and comparing it with the previously determined protein G sequence. The 40 N-terminal amino acids were found to be identical with an amino acid sequence starting at position 62 in the protein G molecule. These and previous data enabled us to locate the albumin binding to the repetitively arranged domains in the N-terminal half of the protein G molecule.     

Novel sulfamethazine ligand used for one-step purification of immunoglobulin G from human plasma

To replace conventional affinity ligand like protein A or protein G, a pseudobioaffinity ligand seems to be an alternative for the purification of immunoglobulin G (IgG). In this study, sulfamethazine (SMZ) was chosen as novel affinity ligand for investigating its affinity to human IgG. Monodisperse, non-porous, cross-linked poly (glycidyl methacrylate) (PGMA) beads were employed as the support for high-performance affinity chromatography. SMZ was immobilized on PGMA beads using bisoxirane (ethanediol diglycigyl ether) as spacer. The resultant affinity media presented minimal non-specific interaction with other proteins. Results of high-performance frontal analysis indicated that the media showed specific affinity to human IgG with a dissociation constant on the order of 10(-6) M. The SMZ affinity column proved useful for a very convenient one-step purification of IgG from human plasma. Antibody purity after a one-step purification was higher than 90%, as determined by densitometric scanning of sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified fraction under reducing condition. The results obtained indicate that SMZ is a valuable affinity ligand for purification of human IgG.     

Streptococcal protein G. Gene structure and protein binding properties

Protein G was solubilized from 31 human group C and G streptococcal strains with the muralytic enzyme mutanolysin. As judged by the mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the binding patterns of the solubilized protein G molecules in Western blot experiments, the strains could be divided into three groups, represented by the group G streptococcal strains G148 and G43 and the group C streptococcal strain C40. The 65-kDa G148 protein G and the 58-kDa C40 protein G showed affinity for both immunoglobulin G (IgG) and human serum albumin (HSA), whereas the 40-kDa G43 protein G bound only IgG. Despite the different molecular patterns, the three protein G species had identical NH2-terminal amino acid sequences. Apart from the 65-kDa peptide, digestion of G148 streptococci with mutanolysin also produced a 52-kDa IgG- and HSA-binding peptide and a 14-kDa HSA-binding peptide. It was demonstrated that these peptides resulted from cleavage of 65-kDa protein G by proteolytic components in the mutanolysin preparation. The protein G genes of the C40 and G43 strains were cloned and sequenced, and their structure was compared to the previously published sequence of the G148 protein G gene. As compared to G148, both the C40 and G43 genes lacked a 210-base pair fragment in the IgG-binding region, accounting for the 10-fold lower affinity of these proteins for IgG. The G43 gene also lacked a 450-base pair fragment in the 5'-end of the gene, explaining why the G43 protein G did not bind HSA. The differences in protein G structure did not correlate with the clinical origin of the strains used in this study. The IgG-binding region of protein G was further mapped. Thus, a peptide corresponding to a single IgG-binding unit was obtained by the cloning and expression of a 303-base pair polymerase chain reaction-generated DNA fragment. The affinity of this 11.5-kDa peptide for human IgG was 8.0 x 10(7) M-1, as determined by Scatchard plots. Finally, a 55-amino acid-long synthetic peptide, corresponding to one of the three repeated domains in the COOH-terminal half of strain G148 protein G, effectively blocked binding of protein G to IgG.     

双峰驼血清IgG亚型的分离纯化及多克隆抗体的制备

双峰驼IgG亚型包含IgG1、IgG2和IgG3,其中IgG2和IgG3为重链抗体,在结构上与IgG1存在显著差异。为获取双峰驼血清中的IgG1、IgG2和IgG3,并分析其抗原特异性和抗体特异性,本文交替使用Protein A和Protein G亲和层析柱,对其分离纯化,并通过聚丙烯酰胺凝胶电泳进行鉴定;之后分别制备兔抗双峰驼IgG1、IgG2和IgG3的多克隆抗体,通过ELISA对制备的多克隆抗体的效价进行测定;最后应用Western blot评估这三个亚型多克隆抗体的特异性,进而对双峰驼血清中IgG1、IgG2和IgG3的抗原特异性进行分析。结果表明,应用Protein A和Protein G亲和层析柱成功分离纯化出双峰驼血清中的IgG1、IgG2和IgG3;并制备兔抗双峰驼IgG1、IgG2和IgG3的多克隆抗体效价均在1∶10000以上,并且所获得的多克隆抗体分别与IgG1、IgG2和IgG3之间均存在交叉反应,但兔抗双峰驼IgG1多克隆抗体较其它两个亚型多克隆抗体特异性低。结果证明,双峰驼IgG1、IgG2和IgG3均具有良好的免疫原性,三者结构虽存在显著差异,但其抗原特性类似。     

Isolation and characterization of a folate receptor from human placenta

While folate binding proteins have been described in serum and a variety of tissues, the function of these proteins is unknown. A particulate folate binding protein from human placenta has been isolated and characterized following solubilization with Triton X-100. The protein was purified 61,000-fold using affinity chromatography on pteroylglutamic acid-Sepharose as the major purification step. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis the purified protein gave a single band with a Mr = 38,500. Stoichiometry of binding indicated that 1 mol of folate was bound per mol of protein. The protein was a glycoprotein that contained 12% carbohydrate. Antiserum was raised in a rabbit, and on immunodiffusion, gave a single precipitin line with the purified placental folate binding protein. Immunoprecipitation studies using this antiserum indicated that the purified placental folate binding protein shared antigenic determinants with both the large Mr and small Mr folate binding proteins from human milk. Immunofluorescent studies with this antiserum and human erythrocytes revealed the presence of an immunologically similar protein on the plasma membrane of these cells suggesting that this protein may function as a folate receptor.     

Protein D of Haemophilus influenzae. A novel bacterial surface protein with affinity for human IgD

Protein D, a novel surface protein of the bacterial species Haemophilus influenzae with affinity for human IgD, was isolated after solubilization with sonication and Sarcosyl-extraction by a single SDS-PAGE step. From 1 ml of packed bacteria was prepared 0.25 mg of purified protein D. The apparent m.w. of protein D was estimated to 42,000 by SDS-PAGE and gel chromatography. Edman degradation cycles of protein D produced no amino acid phenylthiohydantoin derivatives and the amino-terminal end of the single protein D polypeptide chain is thus probably blocked. Protein D differs from all previously described outer membrane proteins (protein 1 to 6) of H. influenzae. Thus, protein D did not react with antibodies against protein 1 or protein 2 and the latter proteins did not bind IgD. Protein D was found to exhibit unique Ig-binding properties. Thus, in dot blots protein D bound four different human IgD myeloma proteins but not IgG, IgM, IgA, IgE, or some additional proteins. On the IgD molecule, constant parts of the H chains both in the Fab and Fc fragments appear responsible for the interaction with protein D. This novel Ig-binding reagent promises to be of theoretical and practical interest in immunologic and microbiologic research.     

Heterogeneity of hypoxanthine guanine phosphoribosyl transferase from human erythrocytes.

Hypoxanthine guanine phosphoribosyl transferase (E.C.: 2.4.2.8) has been purified 4000- to 4500-fold from normal human erythrocytes by three different schemes of protein fractionation. In one scheme, the enzyme was separated by preparative polyacrylamide gel electrophoresis in an LKB Uniphor system and purified by affinity column chromatography employing Sepharose/phosphoribosyl/pyrophosphate. In the second, the enzyme was isolated by isotachophoresis in the presence of Amphiline carrier ampholytes employing a Tris/phosphate/β-alanine ion system. The enzyme was then purified by isotachophoresis in the presence of carrier ampholytes using a Tris/acetate/glycine ion system. The hypoxanthine guanine phosphoribosyl transferase purified by affinity chromatography and isotachophoresis consisted, on immunoelectrophoresis, mainly of one component and had less than 5% impurities. When subjected to analytical polyacrylamide gel electrophoresis, such preparations were resolved into four isoenzymes. In the third scheme, the enzyme was isolated by isoelectric focusing. In this system, the enzyme was also resolved into four isoenzymes. Their isoelectric points were: 5.47, 5.63, 5.74, and 5.84. When subjected to analytical polyacrylamide gel electrophoresis each isoenzyme migrated at a different rate. In sodium dodecyl sulfate gel electrophoresis each isoenzyme yielded one major and one minor band. Protein appearing in the major and minor bands migrated at rates consistent with a molecular size of 33,500 and 26,500, respectively.     

Isolation and purification of cytokinin binding protein from tobacco leaves by affinity column chromatography

Cytokinin binding protein from tobacco leaves was isolated and purified to a single protein by means of affinity chromatography on benzyladenine-linked Sepharose column combined with polyacrylamide gel electrophoresis. In vitro binding of this protein to [¹⁴C] benzyladenine was inhibited remarkably by cold benzyladenine and kinetin and slightly by adenine, but not adenosine. The molecular weight of the protein was determined to be about 4,000 daltons by gel filtration and SDS polyacrylamide gel electrophoresis.     

Process development for the recovery and purification of recombinant protein G.

The domains of protein G from streptococcus which bind immunoglobulin G have been cloned and expressed in Escherichia coli (Fahnestock et al., 1986). Because protein G binds to several animal immunoglobulin G's, it has many immunochemical applications. This report describes process development for large-scale production of this recombinant protein G (also known as GammaBind G). In 200 l cultures of E. coli, this protein G variant was released from the cell into the culture medium by heating at 80 degrees C for 10 min. The concentration was monitored by either a competitive enzyme-linked immunoassay or a liquid chromatographic assay. Cross-flow microfiltration with 0.22 micron membrane was used to remove the cells. The protein G-rich permeate from the cross-flow microfilter was purified by affinity chromatography using a 5 l column of IgG-Sepharose 6 Fast Flow, which yielded 16-18 g of protein G per column cycle. The pools of purified protein G were concentrated and desalted using ultrafiltration. The salt-free protein G was then lyophilized as bulk product. The overall recovery through the entire process was 50-64%. The analysis of the final product included sodium dodecyl sulfate polyacrylamide gel electrophoresis, UV-visible spectrum, high performance gel filtration, endotoxin level and binding efficiency to human IgG Sepharose.     

Microfibril-associated protein 4 is present in lung washings and binds to the collagen region of lung surfactant protein D.

We have purified a glycoprotein from bovine lung washings using affinity chromatography on a maltose-affinity column. On SDS-polyacrylamide gel electrophoresis the protein showed a molecular mass of 36 kDa in the reduced state and 66 kDa in the unreduced state. On gel permeation chromatography the apparent molecular mass was 250 kDa. N-terminal sequencing showed homology to the human matrix protein microfibril-associated protein (hMFAP4), and the glycoprotein was designated bovine MFAP4 (bMFAP4). Lung surfactant protein D (SP-D) was also purified from lung washings, and calcium-dependent binding was demonstrated between bMFAP4 and SP-D. hMFAP4 was cloned, and recombinant hMFAP4 showed the same binding pattern to SP-D as bMFAP4. No binding was seen to recombinant SP-D composed of the neck region and carbohydrate recognition domain of SP-D, indicating that the interaction between MFAP4 and SP-D is mediated via the collagen region of SP-D. MFAP4 also showed calcium-dependent binding to mannan, which was partially inhibited by maltose. Our findings indicate that MFAP4 has two binding specificities, one for collagen and one for carbohydrate, and we suggest that MFAP4 may fix the collectins in the extracellular compartment during inflammation.     

Detection of an immunoglobulin-like serum protein possessing a high affinity for collagen

Fibronectin isolated from bovine serum by affinity chromatography on collagen-Sepharose was found to contain a great number of concomitant proteins. Polyacrylamide gel electrophoresis of experimental samples pretreated with beta-mercaptoethanol under denaturation conditions resulted in the polypeptide fractions with Mr of 25, 54 and 82 KD, while the non-treated samples contained only one protein of non-fibronectin type (Mr = = 180-190 KD). This protein was isolated from the total preparations of collagen-binding proteins by the procedures generally employed for the isolation of purified preparations of immunoglobulins G; this protein was also isolated from purified immunoglobulins G using affinity chromatography on collagen-Sepharose. In terms of its molecular weight, subunit composition and immunological and chromatographical behaviour this protein can be related to immunoglobulins. The immunoglobulin-like protein isolated together with fibronectin revealed an affinity for denatured collagen, but not for fibronectin or Sepharose. The content of immunoglobulin with an affinity for denatured collagen in the total fraction of immunoglobulins G is 0.3-0.5%.     

Purification and characterization of protein Z from rabbit liver cytosol

Protein Z was purified from rabbit liver cytosol by affinity chromatography on oleic acid-agarose and preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After removal of sodium dodecyl sulfate, the renatured protein was found to bind heme and bilirubin with a Kd of approximately 1 microM which produced large red shifts in their absorption spectra. On isoelectric focusing, rabbit protein Z exhibited two main bands with pI around 6.0.     

Improved method for rapid purification of protein kinase from streptomycetes

Protein kinase from Streptomyces lincolnensis was purified nearly to homogeneity using a high performance liquid chromatography (HPLC) and a Pharmacia FPLC system. The procedure used employed column chromatography on DE-53, followed by FPLC affinity chromatography with serine- or threonine-Sepharose (prepared as described in this paper) and gel filtration using a Superose 12 or TSK G3000SW column. Starting with 3.5 g of mycelial proteins, ∼ 1 mg of pure enzyme was obtained. The procedure is simple and highly reproducible. The protein kinase thus obtained was nearly pure by silver staining after sodium dodecyl sulfate-polyacrylaminde gel electrophoresis. The purified protein kinase phosphorylated substrate proteins at the seryl residues.     

Solubilization of IgG-binding proteins from group A and G streptococci

The release of IgG-binding proteins from the cell surface of streptococcal strains AR-1 and G148 with various proteolytic enzymes, acid, alkali or SDS was investigated. The IgG-binding proteins were purified by affinity chromatography using IgG-Sepharose Fast Flow. After SDS-polyacrylamide gel electrophoresis and immuno-electroblotting the major proteins identified varied in relative molecular mass from 15,000 to 65,000 depending on the solubilizing agent used. The results showed that solubilization with trypsin gave the highest yield of IgG-binding proteins, that strain G148 yielded about twice the amount of protein as strain AR-1, and that elastase released an IgG-binding protein of high relative molecular mass of 65,000.     

Isolation and partial characterization of an amphiphilic 56-kDa fatty acid binding protein from rat renal basolateral membrane

We have identified a 56-kDa fatty acid binding protein in rat renal basolateral membrane and purified it by extraction in nonionic detergent (Triton X-100), followed by gel filtration, DEAE-cellulose chromatography, and affinity chromatography. The purified protein was homogeneous on polyacrylamide gel electrophoresis in the presence of Triton X-100 or SDS. It showed amphiphilic properties on gel filtration, polyacrylamide gel electrophoresis, and oleate-Sepharose 4B chromatography. Its molecular mass was estimated to be 56 kDa by SDS-polyacrylamide gel electrophoresis. The protein showed optimal binding activity at pH 7.5 and 37 degrees C. The apparent Kd for palmitic acid was 0.79 microM. It was immunologically clearly distinct from renal cytosolic fatty acid binding protein.     

G蛋白亲和色谱法纯化动物血清、抗体效果比较

比较 Hitrap G蛋白 Sepharose亲和色谱系统对不同动物血清或腹水的纯化效果 ,为抗体纯化提供依据。结果显示 ,G蛋白对不同动物血清 Ig G吸附能力不同 ,体现在单位体积抗体回收量明显不同 ,这一特点与 A蛋白亲和色谱系统相似。该方法简便快速 ,纯化抗体纯度高 ,免疫活性好 ,色谱柱可反复使用多次     

Isolation of a low molecular mass vasoactive intestinal peptide binding protein.

A vasoactive intestinal peptide (VIP) binding protein was purified in active form by detergent solubilization of lung membranes, gel filtration, VIP-Sepharose affinity chromatography, reverse phase high performance liquid chromatography, and anion exchange chromatography. The mass of this protein was estimated at 18 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 17 kDa by gel filtration. The binding of VIP by this protein was inhibited by Mg2+, covalent cross-linking of [Tyr10-125I]VIP to the protein produced two radioactive bands at 22 and 26 kDa identified by electrophoresis, and the purified protein exhibited saturable and high affinity binding of VIP and the related neuropeptide, rat growth hormone releasing factor.     

两种果子狸血清IgG纯化方法 的比较

目的 探讨一种具有简便快捷、高纯度、活性好的果子狸血清IgG纯化方法。方法 比较Hitrap Protein A亲和层析和PAGE电泳两种纯化法对果子狸血清IgG的纯化,用PAGE还原电泳和Western-Blot法对IgG作纯度鉴定。结果 对Hitrap Protein A纯化的果子狸血清IgG,其活性虽好,但纯度不高;而非还原PAGE电泳所纯化的果子狸血清IgG不但纯度高（〉95%）、并具有较强的免疫活性。结论 非还原PAGE电泳法纯化果子狸血清IgG,是一种具有高纯度、免疫活性强的纯化方法 。     

Actin affinity chromatography in the purification of human, avian and other mammalian plasma proteins binding vitamin D and its metabolites (Gc globulins).

The human plasma protein binding vitamin D and its metabolites (Gc globulin; group-specific component) has been isolated from human plasma by column affinity chromatography on gels to which monomeric actin was covalently attached. Rabbit skeletal-muscle G-actin was covalently coupled to amino-agarose gels before the application of human plasma. At actin/protein molar ratios of 4-8:1, excellent recovery (approximately 58%) of purified binding protein was achieved. After 0.75 M-NaCl washes, the binding protein was eluted from the columns in 3 M-guanidinium chloride, dialysed and analysed. These eluates contained the binding protein as 34-100% of the total protein, reflecting a 130-fold average purification in this single step. In the presence of Ca2+, gelsolin (another plasma protein that binds actin) was apparently retained by the affinity column, but this was prevented by chelation of plasma Ca2+. The actin affinity step also was effective in the isolation of the binding protein from rat, rabbit and chicken plasma, as indicated by autoradiographs of purified fractions analysed by gel electrophoresis after incubation with 25-hydroxy[26,27-3H]cholecalciferol. Further isolation by hydroxyapatite chromatography yielded a purified binding protein which displayed characteristic binding activity toward vitamin D metabolites and G-actin, and retained its physicochemical features. This brief purification sequence is relatively simple and efficient, and should prove to be useful to investigators studying this interesting plasma protein.