Active papain renatured and processed from insoluble recombinant propapain expressed in Escherichia coli.

For the first time the pro-form of a recombinant cysteine proteinase has been expressed at a high level in Escherichia coli. This inactive precursor can subsequently be processed to yield active enzyme. Sufficient protein can be produced using this system for X-ray crystallographic structure studies of engineered proteinases. A cDNA clone encoding propapain, a precursor of the papaya proteinase, papain, was expressed in E. coli using a T7 polymerase expression system. Insoluble recombinant protein was solubilized in 6 M guanidine hydrochloride and 10 mM dithiothreitol, at pH 8.6. A protein-glutathione mixed disulphide was formed by dilution into oxidized glutathione and 6 M GuHCl, also at pH 8.6. Final refolding and disulphide bond formation was induced by dilution into 3 mM cysteine at pH 8.6. Renatured propapain was processed to active papain at pH 4.0 in the presence of excess cysteine. Final processing could be inhibited by the specific cysteine proteinase inhibitors E64 and leupeptin, but not by pepstatin, PMSF or EDTA. This indicates that final processing was due to a cysteine proteinase and suggests that an autocatalytic event is required for papain maturation.     

Expression and purification of recombinant 3C proteinase of Coxsackievirus B3.

We have cloned various lengths of coxsackievirus B3 cDNA encompassing the region encoding the 3C proteinase, which is essential to the viral replication cycle. Such viral cDNAs were fused in frame to the 5'terminal portion of the lacZ' gene carried on the vector pUC118 to express mature 3C proteinase in Escherichia coli. In the E. coli cells containing pCXB108 or pCXB117, constructed for this study, a large amount of 23-kDa protein was synthesized in the presence of IPTG. This protein was purified and was shown to be intact 3C proteinase. These data suggest that 3C proteinase, expressed as a part of a fusion protein, was active in E. coli and released itself from the precursor fusion protein by autocatalytic cleavage.     

Solid phase synthesis of the proteinase of bovine leukemia virus. Comparison of its specificity to that of HIV-2 proteinase.

The 126-residue proteinase (PR) of bovine leukemia virus (BLV) was synthesized by solid-phase peptide synthesis and its activity was shown using various oligopeptide substrates representing cleavage sites in BLV, human T-cell leukemia virus type 1 (HTLV-1), murine leukemia virus (MuLV) and human immunodeficiency virus type 1 (HIV-1). The specificity of the BLV PR was also compared to that of chemically synthesized human immunodeficiency virus type 2 (HIV-2) PR. Many of the peptides were cleaved at the expected site, however, 6 out of 15 were hydrolyzed only by one of the PRs. Furthermore, one BLV peptide was processed differently by the two enzymes. These results, together with the relative activities and the lack of inhibition of BLV PR by two HIV-1 PR inhibitors, suggest that the BLV PR specificity is substantially different from that of HIV PRs.     

Propanediol oxidoreductases of Escherichia coli, Klebsiella pneumoniae and Salmonella typhimurium. Aspects of interspecies structural and regulatory differentiation.

The enzyme propanediol oxidoreductase, which converts the lactaldehyde formed in the metabolism of fucose and rhamnose into propane-1,2-diol under anaerobic conditions, was investigated in Escherichia coli, Klebsiella pneumoniae and Salmonella typhimurium. Structural analysis indicated that the enzymes of E. coli and K. pneumoniae have the same Mr and pI, whereas that of Salm. typhimurium also has the same Mr but a slightly different pI. One-dimensional peptide mapping showed identity between the E. coli and K. pneumoniae enzymes when digested with alpha-chymotrypsin, Staphylococcus aureus V8 proteinase or subtilisin. In the case of Salm. typhimurium, this held only for the subtilisin-digested enzymes, indicating that the hydrophobic regions were preserved to a considerable extent. Anaerobically, the three species induced an active propanediol oxidoreductase when grown on fucose or rhamnose. An inactive propanediol oxidoreductase was induced in Salm. typhimurium by either fucose or rhamnose under aerobic conditions, and this was activated once anaerobiosis was established. An inactive propanediol oxidoreductase was also induced in E. coli under aerobic conditions, but only by growth on fucose. The inactive enzyme was not induced by either of the sugars in K. pneumoniae.     

Synthesis of PHB by recombinant E. coli harboring an approximately 5 kb genomic DNA fragment from Streptomyces aureofaciens NRRL 2209

An approximately 5.0 kb Sau3A I genomic DNA fragment from Streptomyces aureofaciens NRRL 2209 was cloned in a plasmid vector and introduced into Escherichia coli. The recombinant E. coli accumulated polyhydroxyalkanoates (PHAs) as cytoplasmic inclusions. The accumulated PHA was identified as the isotactic homopolymer of PHB with a molecular weight of 2.85x10(5). Purified PHB granules were spherical with an average size of 1.1 microm and of stable configuration. DSC thermogram suggested high crystalline nature of the polymer. Maximum thermal degradation of the biopolymer occurred between 250 and 340 degrees C. Recombinant E. coli cells preferentially utilized glycerol as the carbon source and accumulated 25-28 times more PHB than the native S. aureofaciens.     

Expression of human metallothionein III and its metalloabsorption capability in Escherichia coli

Human metallothionein III (MT III) gene was synthesized with Escherichia coli preference codon usage and expressed in E. coli in glutathione-S-transferase (GST) fusion form. The recombinant MT III was released by proteinase Factor Xa digestion and purified with the yield of 2 mg/L culture, and its specific Cd2+ binding capability was confirmed. E. coli strain BL21(DE3), expressing MT III, showed metal tolerance between 0.1 and 0.5 mM Cd2+ and bacterial growth was inhibited at 1 mM Cd2+. MT III expressing E. coli strain showed binding discrimination between different metal ions in combination use, with the preference order of Cd2+ > Cu2+ > Zn2+. It absorbed different metal ions with relatively constant ratio and showed a cumulative absorption capability for mixed heavy metals.     

Expression of bovine leukemia virus protein p24 in Escherichia coli and its use in the immunoblotting assay.

The gag gene encoded protein, p24 of bovine leukemia virus (BLV), was cloned and expressed as thioredoxin-6xHis-p24 protein in Escherichia coli. The bacterial cells carrying plasmid pT7THis-p24 expressed the protein of 38 kDa that was detected by immunoblotting analysis using anti-p24 monoclonal antibodies and sera from BLV infected cattle and sheep. The purified p24 fusion protein was shown to be sensitive and specific for detection of BLV antibodies in the infected cattle.     

Proteinase,Lipase and Amylase Activities in the Small Intestine of Pigs Suffering from Colienterotoxaemia

The activities of proteinases, lipases, amylases and the activities of proteinase inhibitors, as well as the numbers of Escherichia coli in the contents from the small intestine were examined for pigs suffering from colienterotoxaemia and for healthy pigs. Enzyme activities were determined using an agar diffusion test. Compared with healthy animals the activities of proteinases and amylases in diseased animals were reduced while lipases showed increased activity. In pathologically changed contents showing large numbers of E. coli, proteinases could not be demonstrated; however, proteinase inhibitors were found in these contents. In healthy animals, proteinase inhibitors were not demonstrated in ingesta-con-taining contents. In diseased animals, E. coli were found in large numbers in all parts of the small intestine. In healthy animals, E. coli was demonstrated especially in the posterior part of the small intestine and regularly in small numbers. The possible influence of digestive enzymes, especially proteinases and their inhibitors, on enterotoxins from E. coli is discussed.     

Efficient production of native, biologically active human cystatin C by Escherichia coli

A cDNA encoding the mature human cysteine proteinase inhibitor cystatin C was fused to the coding sequence for the Escherichia coli outer membrane protein A signal peptide, and the recombinant gene was expressed in E. coli under the control of the lambda PR promoter, an optimized Shine-Dalgarno sequence and the lambda cI 857 repressor. When induced at 42 degrees C, such cells expressed large amounts of recombinant cystatin C. The recombinant protein was isolated in high yield and characterized. All physicochemical properties investigated, including the positions of disulfide bonds, indicated that the E. coli derived cystatin C was identical to cystatin C isolated from human biological fluids, except that the proline residue in position three was not hydroxylated. The recombinant protein displayed full biological activity against papain, cathepsin B and dipeptidyl peptidase I.     

Fluorogenic assay for rapid detection of Escherichia coli in food.

An assay procedure to screen for Escherichia coli in foods by using 4-methylumbelliferyl-beta-D-glucuronide (MUG) incorporated into lauryl tryptose (LST) broth was evaluated. The beta-glucuronidase produced by E. coli cleaves the MUG substrate to yield a fluorescent end product. E. coli-negative samples can be identified by lack of fluorescence in LST-MUG within 24 h. MUG was not inhibitory to coliforms and E. coli. Over 1,400 food and dairy samples were tested to compare the standard three-tube most-probable-number procedure with the MUG-containing or non-MUG-containing LST procedure. LST-MUG testing detected a greater number of E. coli, with a lower false-positive rate (1.4%) and in a shorter time, than did the standard procedure. All false-positive results in the LST-MUG testing were attributable to beta-glucuronidase-producing staphylococci. No false-negative result was encountered. Use of MUG in LST broth obviates the EC broth step, allowing a 2.5-day procedure to a completed E. coli test versus the present 4- to 6-day standard most-probable-number method.     

Chemical synthesis of a gene for human stefin A and its expression in E. coli

A DNA containing the coding sequence for the human cysteine proteinase inhibitor stefin A was obtained by enzymic ligation of chemically synthesized deoxyoligonucleotides, using the Khorana ligation method. The 306-bp synthetic gene carries signals for the initiation and termination of its translation. The gene was expressed in E. coli using a cytoplasmic expression vector and stefin A was secreted under the control of the E. coli alkaline phosphatase signal sequence, respectively. The secreted hybrid protein was shown to exhibit biological properties similar to the native protein isolated from human plasma.     

A rapid and inexpensive method for preparing E. coli plasmid-DNA

A simple, rapid and inexpensive scaled up miniprep procedure for preparing pure E. coli plasmid DNA is described. Bacterial cells were subjected to the boiling procedure and high molecular weight RNA was removed by LiCl-precipitation. Residual RNA and proteins were removed by subsequent treatment with RNase A and proteinase K/SDS respectively, followed by Sephadex G-50 and Sepharose 6B-Cl chromatography. The average yield from a 100 ml over-night bacterial suspension was 100 to 150 micrograms for pBR-322 DNA, and 250-500 micrograms for SP-6 derived recombinant plasmids. In addition, the described "scaled up" preparation does not require CsCl-ethidium bromide centrifugation; pure plasmid DNA can be prepared within 1 to 2 days.     

Synthesis of a (desSer1 Ile29 Leu89) chicken cystatin gene, expression in E. coli as fusion protein and its isolation

A synthetic gene coding for the cysteine proteinase inhibitor (desSer1 Ile29 Leu89) chicken cystatin was cloned and expressed in E. coli. The gene was assembled from 12 oligonucleotides and inserted into vector pUC 8. Expression as fusion protein was performed in a temperature-inducible E. coli system. The expression product was synthesized as 20% of total E. coli protein. The fusion protein was purified, the chicken cystatin homologue was split off with CNBr and the N-terminal sequence confirmed up to position 37. The properties of the purified material correspond to those of natural chicken cystatin. The recombinant cystatin variant binds anti-chicken cystatin IgG, is inhibitorily active and displays Ki values with papain and with cathepsin B similar to those determined for natural chicken cystatin.     

Trans activity of the norovirus Camberwell proteinase and cleavage of the N-terminal protein encoded by ORF1

The virus-encoded proteinase of Camberwell virus, a genogroup 2 norovirus, was synthesized in Escherichia coli. The purified proteinase had correct N and C termini and showed trans activity in cell-free assays. trans activity was also demonstrated in COS cells transfected with constructs encoding either the proteinase or a proteinase-polymerase fusion. The N-terminal protein of ORF1 was cleaved in COS cells, possibly at the site E(194)/S.     

Characterization of a human coronavirus (strain 229E) 3C-like proteinase activity.

The RNA polymerase gene of human coronavirus (HCV) 229E encodes a large polyprotein that contains domains with motifs characteristic of both papain-like cysteine proteinases and proteinases with homology to the 3C proteinase of picornaviruses. In this study, we have, first, expressed the putative HCV 229E 3C-like proteinase domain as part of a beta-galactosidase fusion protein in Escherichia coli and have shown that the expressed protein has proteolytic activity. The substitution of one amino acid within the predicted proteinase domain (His-3006-->Asp-3006) abolishes, or at least significantly reduces, this activity. Amino-terminal sequence analysis of a purified, 34-kDa cleavage product shows that the bacterial fusion protein is cleaved at the dipeptide Gln-2965-Ala-2966, which is the predicted amino-terminal end of the putative 3C-like proteinase domain. Second, we have confirmed the proteolytic activity of a bacterially expressed polypeptide with the amino acid sequence of the predicted HCV 229E 3C-like proteinase by trans cleavage of an in vitro translated polypeptide encoded within open reading frame 1b of the RNA polymerase gene. Finally, using fusion protein-specific antiserum, we have identified a 34-kDa, 3C-like proteinase polypeptide in HCV 229E-infected MRC-5 cells. This polypeptide can be detected as early as 3 to 5 h postinfection but is present in the infected cell in very low amounts. These data contribute to the characterization of the 3C-like proteinase activity of HCV 229E.     

Cloning of the bovine leukemia virus proteinase in Escherichia coli and comparison of its specificity to that of human T-cell leukemia virus proteinase

The proteinase of bovine leukemia virus (BLV) was cloned into pMal-c2 vector with N-terminal or with N- as well as C-terminal flanking sequences, and expressed in fusion with maltose binding protein. The proteinase self-processed itself from the fusion protein during expression and formed inclusion bodies. The enzyme was purified from inclusion bodies by cation-exchange chromatography followed by gel filtration. Specificity of the enzyme was compared to that of human T-cell leukemia proteinase type 1. Although the two viruses belong to the same subfamily of retroviruses, the differences in their proteinase specificity, based on kinetics with oligopeptide substrates representing naturally occurring cleavage sites as well as on inhibition pattern, appear to be pronounced.