Purification and characterization of recombinant human interleukin-1 beta produced in Escherichia coli

Recombinant human interleukin-1 beta (rIL-1 beta) produced in Escherichia coli was purified to homogeneity by a combination of mass ion exchange column chromatography, ion exchange and gel filtration high performance liquid chromatography. The purified rIL-1 beta had a molecular weight of 18 kD on SDS-polyacrylamide gel electrophoresis and an isoelectric point of 6.9 on analytical isoelectric focusing. These values were almost same as those of natural interleukin-1 beta. The amino acid composition and amino acid sequence of the amino terminal region were consistent with those deduced from the cDNA sequence. In addition, the primary structure was confirmed by peptide mapping with lysyl-endopeptidase on reverse phase HPLC. Besides rIL-1 beta with amino terminal Ala, two molecular species, [Met0] rIL-1 beta and [desAla1] rIL-1 beta, were also obtained. Biological and physicochemical properties of the three species of rIL-1 beta were compared.     

Purification and characterization of human interleukin-1 beta expressed in recombinant Escherichia coli

The high-level expression of human interleukin-1 beta in Escherichia coli is described. The protein contributes about 12% of the total cell protein and is associated with the soluble cytoplasmic fraction of the cell. A method for the purification of the protein is given which is based on anion- and cation-exchange chromatographies. The isolated protein, shown to be homogeneous by several analytical methods, has been characterized by amino acid analysis, N- and C-terminal sequence analysis and analytical centrifugation. The protein is biologically active as demonstrated by two different in vitro assays, namely, the mononuclear cell factor (IL-1/MCF) assay and lymphocyte activating factor (IL-1/LAF) assay. The specific activities determined with the IL-1/MCF and IL-1/LAF assays, are 2 X 10(7) and 4 X 10(7) units mg-1, respectively.     

Escherichia coli expression and processing of human interleukin-1 beta fused to signal peptides

Escherichia coli expression, processing, and secretion of human interleukin-1 beta (IL-1 beta) fused to the signal peptide of E. coli OmpA or PhoA protein were studied. With fusion to either signal sequence, high-level expression was observed and the products accumulated to about 20% of total cell protein. In the fusion to OmpA leader sequence, more than 50% of the product has the OmpA signal peptide removed precisely. The majority of the processed material is not released by osmotic shock. On the other hand, very little of the material from the fusion to PhoA has the PhoA signal peptide removed. Use of the host with a mutation in prlA or prlF, variation of temperature for cell growth, and alteration of the amino acid residues around the cleavage site do not facilitate processing of the PhoA signal peptide. These results suggest that some component in the PhoA signal peptide, interacting with the Il-1 beta sequence, is interfering with the processing of the signal peptide.     

Stabilisation of human interferon beta synthesis in Escherichia coli by zinc ions

Human interferon beta synthesized in Escherichia coli is unstable and toxic for the bacterial cell. Zinc ions are able to stabilise interferon beta in E. coli probably by inhibiting the action of cell internal proteinase(s) which affect the half-life of this foreign protein. As a result up to one order of magnitude more active IFN-beta can be detected in Zn2+-treated E. coli cells.     

Secretion of interleukin-1 beta and Escherichia coli galactokinase by Streptomyces lividans.

The functionality of the Streptomyces lividans beta-galactosidase signal peptide to direct heterologous protein export was examined. The signal peptide plus eight amino acids of mature protein were sufficient to export not only a naturally exported protein, interleukin-1 beta, but also a naturally occurring cytoplasmic protein, Escherichia coli galactokinase. Interestingly, cells which expressed yet exported galactokinase were phenotypically Gal-. The potential use of the exported galactokinase system for the isolation and characterization of mutations within signal peptides and the export machinery of the host is discussed.     

Bacillus stearothermophilus plasmid pSTK1 replicon is functional in Escherichia coli

Summary A kanamycin-resistant plasmid possessing a thermostable replicon derived from Bacillus stearothermophilus cryptic plasmid pSTK1 was constructed. The plasmid could transform not only B. stearothermophilus and Bacillus subtilis, but also Gram-negative Escherichia coli. The behavior of the plasmid in the hosts was examined. The plasmid was stably maintained even at 67°C in B. stearothermophilus without selective pressure. During the plasmid replication, single-stranded DNA (ssDNA) intermediates were found in E. coli, while these were not found in B. subtilis.     

Purification and characterization of human interleukin-1 alpha produced in Escherichia coli

The production of human interleukin-1 alpha (IL-1 alpha) in Escherichia coli is described together with a method for its purification. The isolated protein was shown to be pure and physically homogeneous. The in vitro biological activity of IL-1 alpha was tested with the mononuclear-cell factor and the lymphocyte-activating factor assays. The specific activity determined with both assays was about 3 X 10(7) units mg-1 and is similar to that observed with recombinant human IL-1 beta. The purified protein was resolved by chromatofocusing into two species of isoelectric points 5.45 and 5.20 (75% and 25%, respectively, of the total protein). Both species had similar chemical properties and biological activities to the unfractionated protein. The charge difference between the species was attributed to the deamidation of a single Asn or Gln residue.     

Interleukin-1 beta induces synthesis and secretion of interleukin-6 in human chondrocytes

Increased concentrations of interleukin-6 (IL-6) have been found in the synovial fluid of patients with osteoarthritis, rheumatoid arthritis and crystal-related joint diseases. It is therefore of great interest to identify the cells responsible for the production of IL-6, and to investigate whether IL-6 plays a role in the pathogenesis of degenerative or inflammatory joint diseases. Here we show that human interleukin-1 beta (IL-1 beta) induces IL-6 synthesis and secretion in differentiated human chondrocytes. In organ cultures resembling closely the in vivo system 10(6) chondrocytes incubated with 100 units of interleukin-1 beta per ml of medium led to the release of 6 X 10(3) units of IL-6 within 24 h. Chondrocytes cultured in agarose or as monolayers similarly incubated with IL-1 beta produced even higher amounts of IL-6: 70 X 10(3) units per 10(6) cells within 24 h. The induction of IL-6 synthesis by IL-1 beta was also shown at the mRNA level. IL-6 secreted by stimulated chondrocytes showed heterogeneity upon Western blot analysis.     

Purification of human interleukin-4 produced in Escherichia coli

An interleukin-4 (IL4)-encoding cDNA isolated from human splenocytes was used to construct an expression plasmid that directs a high-level synthesis of mature IL4 protein in Escherichia coli. The expression was under the control of the major leftward promoter, pL, of phage lambda and the phage Mu ribosome-binding site. The IL4 protein was present as insoluble inclusion bodies in the bacterial extract. The IL4 could be solubilized in 5 M MgCl2 and was purified to homogeneity by several chromatographic steps. The yield of protein from bacteria ranged between 3 and 5 mg of IL4 protein per gram of wet cells. The specific activity of the recombinant human IL4 was about the same as that of the natural product.     

Purification of Escherichia coli amplifiable plasmids by high-salt Sepharose chromatography

This new method allows an easy and rapid purification of amplifiable Escherichia coli plasmids such as pBR 322 without the use of cesium chloride centrifugation. After gentle lysis, centrifugation, and phenol extraction, the material is reextracted with acid phenol to remove the bacterial DNA. The high-molecular-weight ribosomal RNA is removed by precipitation with 2 m ammonium sulfate and the tRNA by passage through a small column of Sepharose CL 4B in the presence of 2 m ammonium sulfate.     

Expression in Escherichia coli of fully active recombinant human IL 1 beta: comparison with native human IL 1 beta

Although complementary DNA (cDNA) encoding human interleukin 1 beta (IL 1 beta) have been cloned in several laboratories, there are as yet no data demonstrating that recombinant IL 1 beta (rIL 1 beta) molecules expressed from such cDNA are faithful, fully active replicas of the native protein secreted by human monocytes. To this purpose, cDNA sequences corresponding to the exact NH2-terminus and amino acid sequence of mature, monocyte-derived human IL 1 beta were placed under control of the inducible trp-lac (TAC) fusion promoter and were expressed in E. coli strain JM105. rIL 1 beta was purified to homogeneity by high pressure liquid chromatography (HPLC). Yields of 10 to 20 mg of rIL 1 beta/liter/10(11) cells were obtained. Purified rIL 1 beta was then compared in a number of biochemical and biologic assays to purified native IL 1 beta. Native and rIL 1 beta co-migrated on SDS-polyacrylamide gels as 17.5 kd polypeptides and reacted with specific polyclonal antisera raised to three synthetic peptides of human IL 1 beta in immunoblot experiments. Amino acid sequence analysis of rIL 1 beta showed that the native amino terminus, an ALA residue, was faithfully maintained. Purified native and rIL 1 beta co-chromatographed on reverse-phase HPLC. Specific biologic activities of rIL 1 beta were indistinguishable from those of the native protein in murine thymocyte and human dermal fibroblast proliferation assays, with half-maximal stimulation occurring at concentrations of 25 pM in the murine thymocyte assay and 2 pM in the human dermal fibroblast assay. Similarly, native and rIL 1 beta competed equally well for high affinity IL 1 receptor binding sites, each exhibiting a Ki of 20 pM on MRC-5 human embryonic lung fibroblasts. These observations indicate that E. coli efficiently expresses large quantities of rIL 1 beta, which emulates exactly the properties of the native protein.     

Design of simple synthetic RNA thermometers for temperature-controlled gene expression in Escherichia coli

RNA thermometers are thermosensors that regulate gene expression by temperature-induced changes in RNA conformation. Naturally occurring RNA thermometers exhibit complex secondary structures which are believed to undergo a series of gradual structural changes in response to temperature shifts. Here, we report the de novo design of considerably simpler RNA thermometers that provide useful RNA-only tools to regulate bacterial gene expression by a shift in the growth temperature. We show that a single small stem-loop structure containing the ribosome binding site is sufficient to construct synthetic RNA thermometers that work efficiently at physiological temperatures. Our data suggest that the thermometers function by a simple melting mechanism and thus provide minimum size on/off switches to experimentally induce or repress gene expression by temperature.     

Differential biological activities of human interleukin-1 alpha and interleukin-1 beta

We examined the biological effects induced by both human recombinant interleukin-1 alpha (IL-1 alpha) and beta (IL-1 beta) in five different cell types of human, rat and mouse origin. IL-1 alpha and beta preparations were standardized in terms of biological activity in the EL-4/CTLL bioassay and, in parallel, employed to stimulate PGE2 secretion in human fibroblasts, mesangial cells (MC), C57B1/6 mouse MC, DBA/2 mouse macrophages and Sprague Dawley rat MC. In addition, the co-mitogenic effects of IL-1 alpha and beta were determined in freshly prepared Sprague Dawley rat thymocytes. No significant differences in IL-1 alpha and beta concentration dependent PGE2 production were detectable in the different cell types (MC, fibroblasts and macrophages) of human or mouse origin. Incubation of Sprague Dawley rat MC with both IL-1 alpha and beta resulted in a concentration dependent production of PGE2. However, in contrast to mouse or human MC the potency of IL-1 beta to induce PGE2 in Sprague Dawley rat MC was 26-fold higher compared to IL-1 alpha. In addition, the potency of IL-1 beta to enhance co-stimulated proliferation of Sprague Dawley thymocytes was 200-fold higher than that of equal biological activities of IL-1 alpha. When we tested the additive effects on Sprague Dawley cells, increasing IL-1 beta concentrations added to a fixed IL-1 alpha concentration resulted in a cumulative rise in both, PGE2 secretion by MC and thymocyte proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)     

A novel replicon occurring naturally in Escherichia coli is a phage-plasmid hybrid.

A novel DNA replicon in Escherichia coli was identified. It is the smallest natural isolate (1282 bp) found so far. In the presence of phage M13 it grows as a filamentous single-stranded DNA phage. Contrary to previously identified mini-phages this replicon displays sequence homology only to parts of the M13 viral and complementary strand origin. In the absence of M13 this DNA replicates autonomously. The only gene (arp) of the replicon encodes a 32-kd protein, which is essential for autonomous replication. The host rep gene required for replication of single-stranded DNA phages is dispensable. Distinct replication mechanisms are thus involved during growth as defective phage or as autonomous plasmid.     

Crystallization of purified recombinant human interleukin-1 beta

The gene for human interleukin-1 beta was cloned from SK-hep-1 hepatoma cellular RNA and expressed at high levels in Escherichia coli both as the naturally processed form (rIL-1 beta) and as a variant with an additional sequence of three amino acids on the N-terminus (rIL-1 beta +). Expressed protein was purified to homogeneity by a sequence of steps, which included low pH incubation, adsorption and desorption from Procion Red Sepharose, sizing on a Superose 12 fast-performance liquid chromatography (FPLC) column, and anion exchange chromatography on QAE Sepharose. The final step provided a biologically active protein that migrates on two-dimensional (2-D) gels as a single spot with a pI of 6.7 +/- 0.2 and a molecular mass of 17,500 daltons. Concentrated solutions of rIL-1 beta have produced crystals by ammonium sulfate precipitation. The crystals are tetragonal, show the symmetry of space group P4(1) or its enantiomer, have lattice constants of a = 58.46 (1) and c = 77.02 (3) A, and scatter to at least 2 A resolution. A structure determination based on these crystals is under way.     

Factors affecting the synthesis of the n-terminal methionine-free molecule of recombinant human interleukin-2 by Escherichia coli

Escherichia coli harboring the gene encoding human interleukin-2 (IL-2) produces a mixture of two recombinant IL-2 species: one with the amino-terminal alanine (rIL-2) and the other having an additional methionine residue at the amino terminus (Met-rIL-2). Ways to increase the amount of rIL-2 and its proportion to the total IL-2 were tried. Among E. coli K-12 derivatives, N4830 was an effective producer of recombinant IL-2. The production of the mixture was greatly increased by optimizing the medium ingredients or culture conditions. However, the percentage of rIL-2 in the product decreased almost linearly with an increase of the total production of recombinant IL-2 and was less than 10% under optimal culture conditions. By adding 4.1 × 10⁻⁵ M maganese and 7.4 × 10⁻⁵ M ferric ions to the medium, we succeeded in raising the percentage of rIL-2 to 50% without any decrease of the total production.     

Cloning of cysE gene of Escherichia coli with a mini-Mu-lac containing a plasmid replicon

The restriction map of cysE gene of Escherichia coli was established after cloning a mini-Mu-lac bacteriophage containing a plasmid replicon and recloning on pBR322 vector plasmid. Enzyme assays of transformants indicated the lack of autoregulation of cysE gene.     

Plasmid replicon typing of commensal and pathogenic Escherichia coli isolates

Despite the critical role of plasmids in horizontal gene transfer, few studies have characterized plasmid relatedness among different bacterial populations. Recently, a multiplex PCR replicon typing protocol was developed for classification of plasmids occurring in members of the Enterobacteriaceae. Here, a simplified version of this replicon typing procedure which requires only three multiplex panels to identify 18 plasmid replicons is described. This method was used to screen 1,015 Escherichia coli isolates of avian, human, and poultry meat origin for plasmid replicon types. Additionally, the isolates were assessed for their content of several colicin-associated genes. Overall, a high degree of plasmid variability was observed, with 221 different profiles occurring among the 1,015 isolates examined. IncFIB plasmids were the most common type identified, regardless of the source type of E. coli. IncFIB plasmids occurred significantly more often in avian pathogenic E. coli (APEC) and retail poultry E. coli (RPEC) than in uropathogenic E. coli (UPEC) and avian and human fecal commensal E. coli isolates (AFEC and HFEC, respectively). APEC and RPEC were also significantly more likely than UPEC, HFEC, and AFEC to possess the colicin-associated genes cvaC, cbi, and/or cma in conjunction with one or more plasmid replicons. The results suggest that E. coli isolates contaminating retail poultry are notably similar to APEC with regard to plasmid profiles, with both generally containing multiple plasmid replicon types in conjunction with colicin-related genes. In contrast, UPEC and human and avian commensal E. coli isolates generally lack the plasmid replicons and colicin-related genes seen in APEC and RPEC, suggesting limited dissemination of such plasmids among these bacterial populations.