Purification of the intact monomeric 110 kDa form of the androgen receptor from calf uterus to near homogeneity

In the present study, culf uterine tissue has been used for isolation of androgen receptors. This tissue appeared to be a favourable source for large-scale purification of androgen receptors, because of the relatively high level of androgen receptors and the low concentration of proteolytic enzymes. The purification involved differential phosphocellulose and DNA affinity chromatography as first steps. The non-transformed receptor was passed through these matrices in order to remove contaminating DNA-binding proteins. After a transformation step to the DNA-binding state, the receptor was bound to DNA cellulose and subsequently eluted with MgCl₂. A 0.5% pure androgen receptor preparation was obtained. Photoaffinity labelling with [³H]R1881 (methyltrienolone) was used to determine the size of the receptor at this stage of purification and during the following steps. Subsequently, isoelectric focussing of the partially purified androgen receptor preparation in an aqueous glycerol gradient was performed. In this step, the progesterone receptor, which is copurified with the androgen receptor protein during the first part of the purification procedure, focussed at pH 5.5, while the androgen receptor could be isolated at pH 5.8. The isoelectric focussing procedure could be applied in a preparative way for further purification of androgen receptors. After this step an approx. 8% pure preparation was obtained. Polyacrylamide gel electrophoresis of S-carboxymethylated androgen receptor was used as the final purification step. The [³H]methyltrienolone labelled androgen receptor from calf uterus was purified to homogeneity and consisted of one polypeptide with a molecular mass of 110 kDa.     

Eglin C与2709碱性蛋白酶相互作用分析及亲和纯化方法

Eglin C是来自水蛭中的一种小型热稳定蛋白质,属于马铃薯胰凝乳蛋白酶抑制剂家族,可以抑制弹性蛋白酶、枯草杆菌蛋白酶、组织蛋白酶、α-lytic蛋白酶以及胰凝乳蛋白酶等.然而,利用eglin C纯化蛋白酶,尚未见研究报道.本文将化学合成的编码eglin C及其突变体的基因序列,克隆到原核表达载体pQE30,在大肠杆菌...     

Removal of N-terminal polyhistidine tags from recombinant proteins using engineered aminopeptidases

We have developed a specific and efficient method for complete removal of polyhistidine purification tags (HisTags) from the N-termini of target proteins. The method is based on the use of the aminopeptidase dipeptidyl peptidase I (DPPI), either alone or in combination with glutamine cyclotransferase (GCT) and pyroglutamyl aminopeptidase (PGAP). In both cases, the HisTag is cleaved off by DPPI, which catalyzes a stepwise excision of a wide range of dipeptides from the N-terminus of a peptide chain. Some sequences, however, are resistant to DPPI cleavage and a number of mature proteins have nonsubstrate N-termini which protects them against digestion. For such proteins, HisTags composed of an even number of residues can be cleaved off by treatment with DPPI alone. When the target protein is unprotected against DPPI, a blocking group is generated enzymatically from a glutamine residue inserted between the HisTag and the target protein. A protein with a HisTag-Gln extension is incubated with both DPPI and GCT. As above, the polyhistidine sequence is cleaved off by DPPI, but when the glutamine residue appears in the N-terminus, it is immediately converted into a pyroglutamyl residue by an excess of GCT and further DPPI digestion is prevented. The desired sequence is finally obtained by excision of the pyroglutamyl residue with PGAP. All the enzymes employed can bind to immobilized metal affinity chromatography (IMAC) matrices, and in this paper we demonstrate a simple and highly effective process combining IMAC purification of His-tagged proteins, our aminopeptidase-based method for specific excision of HisTags and use of subtractive IMAC for removing processing enzymes. Typical recoveries were 75-90% for the enzymatic processing and subtractive IMAC. The integrated process holds promises for use in large-scale production of pharmaceutical proteins because of a simple overall design, use of robust and inexpensive matrices, and use of enzymes of either recombinant or plant origin.     

Purification and characterization of outer membrane protein P6, a vaccine antigen of non-typeable Haemophilus influenzae

Outer membrane protein P6 is a promising vaccine antigen with potential to prevent infections caused by non-typeable Haemophilus influenzae. A convenient and reliable method for the purification of P6 and an assessment of the purity, yield, protein structure, antigenicity and immunogenicity of the purified protein are described. The method begins with intact H. influenzae and utilizes a series of incubations and centrifugations using a single buffer to remove all cell components with the exception of the peptidoglycan to which the P6 is associated. P6 is dissociated from the complex with heat and the insoluble peptidoglycan is removed by centrifugation. The procedure yields highly purified P6. Contamination with lipooligosaccharide is less than 0.025 endotoxin U per microgr P6. The yield of P6 is approximately 2 mg of P6 per l H. influenzae culture. The purified P6 retains both the secondary and tertiary structure as measured by circular dichroism and analysis with monoclonal antibodies. The purified P6 is immunogenic in animals. A convenient method for purifying P6 which retains antigenicity and immunogenicity will be an important tool for future studies of the vaccine potential of P6.     

Purification and characterization of an endopeptidase that has an important role in the carboxyl terminal processing of antihypertensive peptides in Lactobacillus helveticus CM4

AIMS: To purify and characterize a peptidase that can catalyse C-terminal processing of antihypertensive peptide from Lactobacillus helveticus CM4. METHODS AND RESULTS: An endopeptidase which seems to process the carboxyl terminal end of two antihypertensive peptides, Val-Pro-Pro and Ile-Pro-Pro, was purified from Lactobacillus helveticus CM4 by four stages of column chromatography, using synthetic pro-peptide as a substrate. The molecular weight of the purified enzyme was estimated to be 67,000 by SEPHACRYL S-200 and 70,000 by SDS-PAGE analysis. The purified enzyme generated: (i) Val-Pro-Pro from Val-Pro-Pro-Phe-Leu and Val-Pro-Pro-Phe-Leu-Gln-Pro, and (ii) Ile-Pro-Pro from Ile-Pro-Pro-Leu-Thr and Ile-Pro-Pro-Leu-Thr-Gln-Thr, but theses peptides could not be generated from Val-Pro-Pro-Phe, Val-Pro-Pro-Phe-Leu-Gln, Ile-Pro-Pro-Leu and Ile-Pro-Pro-Leu-Thr-Gln. Part of the amino terminal sequence of the purified enzyme had homology to a previously reported pepO gene product. CONCLUSION: These results suggest that the purified endopeptidase isolated in this study have an important role in the carboxyl terminal processing of two antihypertensive peptides in Lact. helveticus CM4.     

Proteomic analysis identifies a new complex required for nuclear pre-mRNA retention and splicing

Using the proteomic tandem affinity purification (TAP) method, we have purified the Saccharomyces cerevisie U2 snRNP-associated splicing factors SF3a and SF3b. While SF3a purification revealed only the expected subunits Prp9p, Prp11p and Prp21p, yeast SF3b was found to contain only six subunits, including previously known components (Rse1p, Hsh155p, Cus1p, Hsh49p), the recently identified Rds3p factor and a new small essential protein (Ysf3p) encoded by an unpredicted split ORF in the yeast genome. Surprisingly, Snu17p, the proposed yeast orthologue of the seventh human SF3b subunit, p14, was not found in the yeast complex. TAP purification revealed that Snu17p, together with Bud13p and a newly identified factor, Pml1p/Ylr016c, form a novel trimeric complex. Subunits of this complex were not essential for viability. However, they are required for efficient splicing in vitro and in vivo. Furthermore, inactivation of this complex causes pre-mRNA leakage from the nucleus. The corresponding complex was named pre-mRNA REtention and Splicing (RES). The presence of RES subunit homologues in numerous eukaryotes suggests that its function is evolutionarily conserved.     

Partitioning of recombinant human granulocyte-macrophage colony stimulating factor (hGM-CSF) from plant cell suspension culture in PEG/sodium phosphate aqueous two-phase systems

Partitioning of human granulocyte-macrophage colony stimulating factor (hGM-CSF) was achieved in the aqueous two-phase systems (ATPSs) using a crude extract of transgenic tobacco cell suspension culture. This study examined the effects of polyethylene glycol (PEG) molecular weight and concentration and the effects of sodium phosphate concentration in different PEG/sodium phosphate systems on the partition coefficient,K. The best ATPS system was 5% PEG 8,000/1.6 M sodium phosphate after 2 h of incubation at room temperature. In this system, hGM-CSF was partitioned in the PEG-rich phase with a yield of 57.99% andK _hGM-CSF of 8.12. In another system, 3% PEG 10,000/1.6 M sodium phosphate, hGM-CSF was also partitioned primarily in the top phase with a yield of 45.66% andK _hGM-CSF of 7.64 after 2 h of incubation at room temperature.     

Fractionation and characterization of kinesin II species in vertebrate brain

Recent research on kinesin motors has outlined the diversity of the superfamily and defined specific cargoes moved by kinesin family (KIF) members. Owing to the difficulty of purifying large amounts of native motors, much of this work has relied on recombinant proteins expressed in vitro. This approach does not allow ready determination of the complement of kinesin motors present in a given tissue, the relative amounts of different motors, or comparison of their native activities. To address these questions, we isolated nucleotide-dependent, microtubule-binding proteins from 13-day chick embryo brain. Proteins were enriched by microtubule affinity purification, then subjected to velocity sedimentation to separate the 20S dynein/dynactin pool from a slower sedimenting KIF containing pool. Analysis of the latter pool by anion exchange chromatography revealed three KIF species: kinesin I (KIF5), kinesin II (KIF3), and KIF1C (Unc104/KIF1). The most abundant species, kinesin I, exhibited the expected long range microtubule gliding activity. By contrast, KIF1C did not move microtubules. Kinesin II, the second most abundant KIF, could be fractionated into two pools, one containing predominantly A/B isoforms and the other containing A/C isoforms. The two motor species had similar activities, powering microtubule gliding at slower speeds and over shorter distances than kinesin I.     

Delineation of ligand binding and receptor signaling activities of purified P2Y receptors reconstituted with heterotrimeric G proteins

P2Y receptors are G protein coupled receptors that respond to extracellular nucleotides to promote a multitude of signaling events. Our laboratory has purified several P2Y receptors with the goal of providing molecular insight into their: (1) ligand binding properties, (2) G protein signaling selectivities, and (3) regulation by RGS proteins and other signaling cohorts. The human P2Y₁ receptor and the human P2Y₁₂ receptor, both of which are intimately involved in ADP-mediated platelet aggregation, were purified to near homogeneity and studied in detail. After high-level expression from recombinant baculovirus infection of Sf9 insect cells, approximately 50% of the receptors were successfully extracted with digitonin. Purification of nearly homogeneous epitope-tagged P2Y receptor was achieved using metal-affinity chromatography followed by other traditional chromatographic steps. Yields of purified P2Y receptors range from 10 to 100 g/l of infected cells. Once purified, the receptors were reconstituted in model lipid vesicles along with their cognate G proteins to assess receptor function. Agonist-promoted increases in steady-state GTPase assays demonstrated the functional activity of the reconstituted purified receptor. We have utilized this reconstitution system to assess the action of various nucleotide agonists and antagonists, the relative G protein selectivity, and the influence of other proteins, such as phospholipase C, on P2Y receptor-promoted signaling. Furthermore, we have identified the RGS expression profile of platelets and have begun to assess the action of these RGS proteins in a reconstituted P2Y receptor/G protein platelet model.