Expression of Pseudomonas fluorescens D-galactose dehydrogenase in E. coli

Functional overexpression and purification of a codon optimized synthetic glucarpidase (carboxypeptidase G2) in Escherichia coli

Glucarpidase (former name: carboxypeptidase G2, or CPG2) is a bacterial enzyme that is widely used in detoxification of the cytotoxic drug, methotrexate, and in Antibody Directed Enzyme Prodrug Therapy for cancer treatment. The glucarpidase gene of Pseudomonas sp. strain RS-16 was previously cloned in E coli, but expresses at a level that is approximately 100-fold lower than in the native strain. In this study, a synthetic gene coding for glucarpidase was codon-optimised and synthesized for maximum expression in E. coli using the vector pET28a. Our work indicated that the enzyme was expressed to ~60% of the total host protein and that purification of the recombinant His-tagged protein could be achieved in a single step by Ni(2+) charged column chromatography. The synthetic recombinant glucarpidase expressed within this system was biologically active and zinc dependant. Our study showed that Mg(2+) as well as Mn(2+) ions inhibit the activity of the recombinant enzyme.

Affinity precipitation and site-specific immobilization of proteins carrying polyhistidine tails

Proteins carrying genetically attached polyhistidine tails have been purified using affinity precipitation with metal chelates. DNA fragments encoding four or five histidine residues have been genetically fused to the oligomeric enzymes lactate dehydrogenase (Bacillus stearothermophilus), beta-glucoronidase (Escherichia coli), and galactose dehydrogenase (Pseudomonas fluorescens) as well as to the monomeric protein A (Staphylococcus aureus). The chimeric genes were subsequently expressed in E. coli. The engineered enzymes were successfully purified from crude protein solutions using ethylene glycolbis (beta-aminoethyl) tetraacetic acid (EGTA) charged with Zn(2+) as precipitant, whereas protein A, carrying only one attached histidine tail, did not precipitate. However, all of the engineered proteins could be purified on immobilized metal affinity chromatography (IMAC) columns loaded with Zn(2+). The potential of using the same histidine tails for site-specific immobilization of proteins was also investigated. The enzymes were all catalytically active when immobilized on IMAC gels. For instance, immobilized lactate dehydrogenase, carrying tails composed of four histidine residues, displaced 83% of the soluble enzyme activity.

Multiple immunoenzyme staining: methods and visualizations for the observation with spectral imaging

Several staining concepts and color combinations exist to perform successful double immunoenzyme staining on human tissue specimens. Most of these concepts are based on differences between both primary antibodies: animal species, mouse Ig isotype or IgG subclasses, conjugates, or concentrations. Traditionally, double immunoenzyme staining has used chromogens selected to provide maximum color contrast when observed with the unaided eye. Unfortunately, visually good color combinations always include at least one diffuse chromogen, because of the paucity of appropriate chromogen colors. This situation is drastically changed with the use of spectral imaging, where multicolor microscopy can be unmixed in individual images based on their spectral characteristics. Spectral unmixing can be performed even up to quadruple immunoenzyme staining. This work contains practical suggestions for immunoenzyme double staining procedures for some frequently encountered primary antibody combinations: rabbit-mouse, goat-mouse, mouse-mouse, and rabbit-rabbit. The suggested protocols are all suitable for a classical red-brown color combination plus blue nuclear counterstain that is composed of peroxidase activity (diaminobenzidine tetrahydrochloride), alkaline phosphatase activity (Liquid Permanent Red), and hematoxylin, respectively. Although the red and brown chromogens do not contrast very well visually, they both show a crisp localization and can be perfectly unmixed by spectral imaging.

NAD(H) recycling activity of an engineered bifunctional enzyme galactose dehydrogenase/lactate dehydrogenase

A chimeric bifunctional enzyme composing of galactose dehydrogenase (galDH; from Pseudomonas fluorescens) and lactate dehydrogenase (LDH; from Bacillus stearothermophilus) was successfully constructed. The chimeric galDH/LDH possessed dual characteristics of both galactose dehydrogenase and lactate dehydrogenase activities while exhibiting hexameric rearrangement with a molecular weight of approximately 400 kDa. In vitro observations showed that the chimeric enzyme was able to recycle NAD with a continuous production of lactate without any externally added NADH. Two fold higher recycling rate (0.3 mM/h) than that of the native enzyme was observed at pH values above 8.5. Proximity effects became especially pronounced during the recycling assay when diffusion hindrance was induced by polyethylene glycol. All these findings open up a high feasibility to apply the NAD(H) recycling system for metabolic engineering purposes e.g. as a model to gain a better understanding on the molecular proximity process and as the routes for synthesizing of numerous high-value-added compounds.

Galactosyl-mimodye ligands for Pseudomonas fluorescens beta-galactose dehydrogenase

Protein molecular modelling and ligand docking were employed for the design of anthraquinone galactosyl-biomimetic dye ligands (galactosyl-mimodyes) for the target enzyme galactose dehydrogenase (GaDH). Using appropriate modelling methodology, a GaDH model was build based on a glucose-fructose oxidoreductase (GFO) protein template. Subsequent computational analysis predicted chimaeric mimodye-ligands comprising a NAD-pseudomimetic moiety (anthraquinone diaminobenzosulfonic acid) and a galactosyl-mimetic moiety (2-amino-2-deoxygalactose or shikimic acid) bearing an aliphatic 'linker' molecule. In addition, the designed mimodye ligands had an appropriate in length and chemical nature 'spacer' molecule via which they can be attached onto a chromatographic support without steric clashes upon interaction with GaDH. Following their synthesis, purification and analysis, the ligands were immobilized to agarose. The respective affinity adsorbents, compared to other conventional adsorbents, were shown to be superior affinity chromatography materials for the target enzyme, Pseudomonas fluorescensbeta-galactose dehydrogenase. In addition, these mimodye affinity adsorbents displayed good selectivity, binding low amounts of enzymes other than GaDH. Further immobilized dye-ligands, comprising different linker and/or spacer molecules, or not having a biomimetic moiety, had inferior chromatographic behavior. Therefore, these new mimodyes suggested by computational analysis, are candidates for application in affinity labeling and structural studies as well as for purification of galactose dehydrogenase.

Immunochemical analyses of serum antibodies from pig herds in a Salmonella non-endemic region

In a large comparative survey of Danish and Swedish slaughter pig herds performed prior to this work, it was unexpectedly found that some Swedish herds harbored seropositive pigs. Serum samples from the Swedish herds had moderate responses in the Salmonella mix-ELISA (detecting serogroup B and C1 infections) compared to the Danish herds classifying some of them as seropositive using a cut-off value at 40 OD%. In Sweden, extensive Salmonella control is carried out by bacteriological screening of feces and lymph nodes, and the overall prevalence has been proven to be below 0.1%. The serological positive results were therefore unexpected; hence the reactivities of the Swedish sera were studied by a number of immunochemical analyses (Western blot, indirect ELISA, inhibition ELISA, avidity ELISA) and compared to sera from Danish pig herds with verified Salmonella infections ("the reference sera"). In Western blot, the Swedish sera had high binding reactivities against Salmonella Typhimurium LPS of different molecular weights, and gave binding patterns similar to that of the reference sera. Pre-incubation with free S. Typhimurium LPS or PS (the polysaccharide part of LPS) was able to inhibit the reactivity of the Swedish sera in the mix-ELISA. Reactivities against other related bacterial LPS such as Citrobacter freundii LPS and Yersinia enterocolitica O:3 LPS were observed in the Swedish sera, but these LPS antigens were unable to inhibit the reactivities in the mix-ELISA as efficiently as S. Typhimurium LPS. Furthermore, the Swedish sera did not bind Salmonella LPS of another serogroup (S. Meleagridis LPS, serogroup E1) or rough Salmonella LPS, both lacking the specific O-antigenic parts of S. Typhimurium LPS. The avidity of the Swedish sera was much lower than the avidity of the reference sera, which could indicate the presence of transient low-dose infections or stimulation by inactivated bacteria in feed. The results obtained in this investigation strongly indicate that the Swedish sera contain antibodies directed against the O-antigenic part of LPS from S. Typhimurium or possibly on as yet unknown bacterium.

The transferrin receptor of Actinobacillus pleuropneumoniae: quantitation of expression and structural characterization using a peptide-specific monoclonal antibody

When Actinobacillus pleuropneumoniae (A. pp) is grown under iron-restricted conditions in vitro, transferrin binding proteins (Tbps) are induced. The functional transferrin receptor of A. pp is composed of two outer membrane proteins (Tbp1 and Tbp2) and shows an exquisite specificity for porcine transferrin. This complex was studied using a monoclonal antibody (Mab 1.48) raised against a synthetic peptide corresponding to a hydrophilic domain of Tbp2 common to several A. pp serotypes. The antibody reacted specifically with a 60-70kDa Tbp2-antigen found in all serotypes of A. pp obtained from iron-restricted culture. It was found that Tbp2 was not expressed in iron replete medium by any serotype except serotypes 5a, 5b and 6 where a weak expression was seen. There was a weak expression of related antigens in Actinobacillus indolicus and Actinobacillus suis under iron-depleted conditions while no similar antigens were detected with the Mab in iron-starved Actinobacillus lignieresii, Actinobacillus porcinus, Actinobacillus minor, Haemophilus influenzae, and Haemophilus parasuis. Using an enzyme-linked immunosorbent assay (ELISA) based on the Mab 1.48, Tbp2 could be detected in both recombinant E. coli expressing Tbp2 and in wild type A. pp grown under iron restricted conditions. The subcellular location of Tbp2 in A. pp was studied by immunoelectron microscopy using the Mab 1.48. Interestingly, all antibody binding was found inside the A. pp cells, while Tbp2 expressed in recombinant E. coli was found both in the cytosol and on the outer membrane. These results indicate that the Mab 1.48-reactive epitope of Tbp2 is surface exposed when it is expressed without Tbp1 in E. coli while the inaccessibility of this epitope of Tbp2 in A. pp could be due to shading by the association between Tbp2 and Tbp1.

The porcine acute phase response to infection with Actinobacillus pleuropneumoniae. Haptoglobin, C-reactive protein, major acute phase protein and serum amyloid A protein are sensitive indicators of infection

In an experimental infection model mimicking acute Actinobacillus pleuropneumoniae (Ap) infection in swine (Sus scrofa) by aerosol inoculation, the development of a number of typical clinical signs was accompanied by a prototypic acute phase reaction encompassing fever and an acute phase protein response peaking at around 2 days after infection. Haptoglobin, C-reactive protein (CRP), and major acute phase protein (MAP) responded with large increases in serum levels, preceding the development of specific antibodies by 4-5 days. Serum amyloid A protein (SAA) was also strongly induced. The increase, kinetics of induction and normalization were different between these proteins. It is concluded that experimental Ap-infection by the aerosol route induces a typical acute phase reaction in the pig, and that pig Hp, CRP, MAP, and SAA are major acute phase reactants. These findings indicate the possibility of using one or more of these reactants for the nonspecific surveillance of pig health status.

Distribution of metallothionein in the human central nervous system

The distribution of metallothionein (MT), a metal-binding protein, was examined immunohistochemically in the normal human brain and spinal cord. Paraffin-embedded brain tissue from three patients who had died from a non-neurological disease and were free of histopathological central nervous system alterations were processed. The results of the present study demonstrate that MT is readily detectable in a subgroup of astrocytes in the normal human brain. MT staining is most intense on grey matter astrocytes that bear short stout processes and which probably represent protoplasmic astrocytes. Using anti-MT and anti-glial fibrillary acidic protein immunostaining, we could demonstrate two subpopulations of astrocytes that were mutually exclusive. The functional significance of MT-expression in protoplasmic astrocytes is not entirely clear. Metal detoxification is only one of the many postulated functions of MT. The finding that staining for MT permits subtyping of astrocytes may be of great importance in glia research and surgical pathology of the human brain.

Pseudomonas aeruginosa promoters which contain a conserved GG-N10-GC motif but appear to be RpoN-independent

The proC gene of Pseudomonas aeruginosa encodes the constitutive delta 1-pyrroline 5-carboxylate reductase (the third enzyme of proline biosynthesis) and ranks among the numerous Pseudomonas genes which are poorly transcribed in Escherichia coli. The promoters of the proC gene were located by deletion mapping. The 5' ends of the proC transcripts originating from one promoter were determined by primer extension. This promoter has a GG-N10-GC motif with a 16 bp spacing between the GC doublet and the transcription start site. Such spacing is unusually long for sigma 54-dependent promoters. In rpoN mutants of P. aeruginosa and P. putida a proC'--'lacZ fusion was expressed at wild-type levels, suggesting that sigma 54 RNA polymerase is not involved in proC transcription. The expression of another P. aeruginosa gene, anr (for anaerobic regulation of nitrate respiration and anaerobic arginine degradation), also appeared to be independent of RpoN in Pseudomonas and occurred at a very low level in E. coli. The proC and anr promoters have sequence similarities in addition to the conserved GG--N10--GC motif and may also be related to some alg (alginate) promoters of P. aeruginosa. We propose that the proC and anr promoters are activated by proteins, including perhaps an alternative sigma factor, which are present in Pseudomonas but absent from E. coli.

Increased expression of the plasmid-determined 2,3-dihydroxybiphenyl dioxygenase gene in strains of Escherichia coli, Pseudomonas putida and Pseudomonas aeruginosa

A 6.5-kb EcoRI fragment containing the gene encoding 2,3-dihydroxybiphenyl dioxygenase from the plasmid pBS312 was cloned into broad host range plasmid RSF1010 and expressed in Escherichia coli, Pseudomonas putida and Pseudomonas aeruginosa strains. The increased expression of the gene was orientation-dependent and probably due to the transcription read through from the streptomycin promoter of the vector. Subcloning experiments of the PstI fragments of pBS312 plasmid using vector pBR322 revealed that the bphC gene encoding 2,3-dihydroxybiphenyl dioxygenase is localized on the 2.1-kb fragment. In Escherichia coli JM109, transformed by the plasmid pBS314 carrying the 2.1-kb insert in orientation which allowed expression of the bphC gene from the ampicillin promoter of pBR322, the enzyme activity of 2,3-dihydroxybiphenyl dioxygenase was ten times higher than that in parental strain Pseudomonas putida SU83. The results presented show the first case of the increased expression of Pseudomonas degradative gene in Escherichia coli.

A two-component T7 system for the overexpression of genes in Pseudomonas aeruginosa

A two-component T7 expression system was developed for efficient expression of genes in the nonenteric bacterium, Pseudomonas aeruginosa. The first component of the expression system is a bacteriophage-based transposable element that contains a lacUV5/lacIq-regulated T7 RNA polymerase gene and a selectable antibiotic-resistance determinant. This element, designated miniD-180, was stably integrated into the P. aeruginosa PAO1 chromosome. The second component of this system includes several improved broad-host-range expression vectors containing the T7 gene 10 promoter and multiple cloning site (MCS). These vectors (pEB8, pEB11, and pEB12) contain transcriptional terminators (T1(4)) upstream from the T7 promoter, and T7 terminators downstream from the MCS. Because the T7 promoter is somewhat leaky in these vectors, pEB14 was constructed to decrease transcription of target genes by basal levels of T7 RNA polymerase. This vector contains a core sequence of the lac operator located 19 bp downstream from the transcriptional start point of the T7 promoter, thereby providing a dually regulated system. The utility of this system was demonstrated by placing a promoterless chloramphenicol acetyltransferase (CAT) cassette under control of the T7 promoter and monitoring the isopropyl-beta-D-thiogalactopyranoside-dependent accumulation of CAT in cell-free extracts of P. aeruginosa. We observed up to nearly a 60-fold increase in CAT levels 4 h post-induction, at which time this polypeptide represented up to 20% of the total soluble protein.

Metal affinity precipitation of proteins carrying genetically attached polyhistidine affinity tails

In this study, galactose dehydrogenase (EC 1.1.1.48) was chosen as a prototype target protein to investigate the capability of metal affinity precipitation to facilitate the purification of genetically engineered proteins. A DNA fragment encoding five histidine residues was fused to the 3'-terminal end of the galactose dehydrogenase gene from Pseudomonas fluorescens and thereafter expressed in Escherichia coli. The additional five histidines functioned as an affinity tail and the modified enzyme could be purified using metal affinity precipitation when the metal-chelate complex with ethylene glycol-bis-(beta-aminoethyl ether) N,N,N',N'-tetra-acetic acid, EGTA(Zn)2, was added to the protein solution. The affinity tail could also be applied for the purification of the fusion protein utilising immobilised metal affinity chromatography. After purification, the pentahistidine affinity tail could be removed enzymatically by carboxypeptidase A. Furthermore, growth rate experiments demonstrated that the expression of the metal-binding affinity tail in E. coli cells enhanced the tolerance to zinc ions when added to the growth medium.

Construction and characterization of a recombinant tripartite enzyme, galactose dehydrogenase/beta-galactosidase/galactokinase

The in-frame gene fusion between 3 enzymes, galactose dehydrogenase, beta-galactosidase and galactokinase, is described. The purified artificial tripartite enzyme displayed all three enzymic activities. Two major forms of the hybrid protein were found, consisting of 4 and 8 subunits respectively, but other forms could also be identified. Each subunit was made up of one monomer each of galactose dehydrogenase, beta-galactosidase and galactokinase. Proximity effects exhibited by the hybrid enzyme could be demonstrated using [14C]galactose as a reporter molecule.

Unorthodox expression of an enzyme: evidence for an untranslated region within carA from Pseudomonas aeruginosa

The genes encoding carbamoylphosphate synthetase from Pseudomonas aeruginosa PAO1 were cloned in Escherichia coli. Deletion and transposition analysis determined the locations of carA, encoding the small subunit, and carB, encoding the large subunit, on the chromosomal insert. The nucleotide sequence of carA and the flanking regions was determined. The derived amino acid sequence for the small subunit of carbamoylphosphate synthetase from P. aeruginosa exhibited 68% homology with its counterparts in E. coli and Salmonella typhimurium. The derived sequences in the three organisms were essentially identical in the three polypeptide segments that are conserved in glutamine amidotransferases but showed low homology at the amino- and carboxy-terminal regions. The amino-terminal amino acid sequences were determined for the large and small subunits. The first 15 amino acids of the large subunit were identical to those derived from the carB sequence. However, comparison of the derived sequence for carA with the amino-terminal amino acid sequence for the small subunit suggested that codons 5 to 8 are not translated. The DNA sequence for the region encompassing these four codons was confirmed by direct sequencing of chromosomal DNA after amplification by the polymerase chain reaction. The mRNA sequence was also deduced by in vitro synthesis of cDNA, enzymatic amplification, and sequencing, confirming that 12 nucleotides in the 5' terminal of carA are transcribed but are not translated.

Construction of an artificial bifunctional enzyme, beta-galactosidase/galactose dehydrogenase, exhibiting efficient galactose channeling

The in-frame fusion between two oligomeric enzymes, beta-galactosidase and galactose dehydrogenase, is described. The lacZ gene was fused to the 3' end of the galdh gene with a linker encoding only three amino acids. The purified artificial bifunctional enzyme displayed the enzymic activity of both gene products. The hybrid protein was found in two major forms, consisting of four and six subunits, but other forms could also be identified. The molecular weight of each subunit was determined to be 145,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bifunctional enzyme shows kinetic advantages over the identical native system in conversion of lactose to galactonolactone. A higher steady-state rate and a reduction of the transient time are observed. This phenomenon is especially pronounced at low initial substrate concentrations and when the pH is adjusted to a level at which the galactose dehydrogenase activity is much higher than that of the beta-galactosidase.

Expression of the plum pox virus coat protein region in Escherichia coli

A cDNA complementary to the 3' end of plum pox virus (PPV) RNA was sequenced. The sequence was investigated for the presumable coat protein cistron by computer-aided translation. A fragment containing the stop codon of the polyprotein gene and a putative virus-specific protease cleavage site was subcloned into an E. coli expression vector. It is shown by immunological analysis that the coat protein cistron is located within the subcloned region.

Use of commercially available monoclonal antibodies for immunoenzyme double staining

An immunoenzyme double-staining method for the simultaneous detection of two cellular epitopes, using commercially available mouse monoclonal antibodies, is described. The method employs a combination of the suppression of endogenous biotin and two successive indirect techniques with a blocking step in between. The first indirect method involves an unlabelled monoclonal antibody followed by an alkaline phosphatase-conjugated goat anti-mouse immunoglobulin. After a blocking step with normal mouse serum, the second indirect method is applied using a biotinylated monoclonal antibody followed by the visualization of this antibody by avidin-biotinylated peroxidase complex (ABC) or rabbit anti-biotin and peroxidase-conjugated swine anti-rabbit immunoglobulin in successive steps. Using these methods in combination with the introduction of dioctyl sodium sulphosuccinate and tetramethylbenzidine as chromogens for peroxidase activity, two cellular epitopes could be distinguished clearly in tissue sections by the green- and violet-stained peroxidase and alkaline phosphatase activities, respectively. The expression of two epitopes on the same cellular constituent is outlined by the coappearance of both enzyme activities as a bluish-purple colour. This method allows for the simultaneous identification, localization and enumeration of two cellular epitopes. These can serve as parameters for a number of pathological processes.

Damaged rat peripheral nerves do not contain detectable amounts of alpha-MSH

Peptides related to alpha-MSH (collectively termed melanocortins) stimulate nerve growth following injury and may play a physiological role in the repair process. Melanocortins are not normally present in mature peripheral nerves but MSH-like bioactivity has been observed in extracts of injured nerves. alpha-MSH could derive from reexpression of the POMC prohormone in injured nerves or from proteolysis of the intermediate-size neurofilament protein that bears antigenic similarities to melanocortins. Using a radioimmunoassay that will distinguish between alpha-MSH and neurofilament-derived fragments, we have shown that alpha-MSH is not present (detection limit 74 pg alpha-MSH/mg protein) in damaged rat sciatic nerves.

Synergistic effect of detergents and aluminium phosphate on the humoral immune response to bacterial and viral membrane proteins

The influence of detergents on the immunogenic activity of the major outer membrane protein of Neisseria gonorrhoeae was investigated. Most detergents tested were found to enhance the immune response. This effect was synergistic with the adjuvant activity of AlPO4. The combination of detergent and AlPO4 showed a stronger adjuvant activity than Freund's complete adjuvant. The adjuvant effect was only observed with protein preparations with very low lipopolysaccharide content. The immunostimulating effect of detergents was also observed with meningococcal group C polysaccharide conjugated to a Haemophilus influenzae type b outer membrane protein and with the fusion protein of measles virus. The influence of some detergent parameters (critical micelle concentration, hydrophile-lipophile balance, charge) was investigated.

Antigenic and immunogenic properties of cyanogen bromide peptides from gonococcal outer membrane protein IB. Evidence for the existence of a surface-exposed conserved epitope

Two distinct species of gonococcal porin proteins exist that differ with regard to surface exposure. Protein IB, expressed by strains of the WII/III serogroup, has both termini buried in the outer membrane, leaving a central region of the molecule exposed at the cell surface. We have attempted to define this region of protein IB in detail by studying the antigenic and immunogenic properties of peptides derived from protein IB. Treatment of gonococcal protein IB (serotype 5) with cyanogen bromide resulted in cleavage of protein IB into three major fragments of Mr of 15,000, 13,000, and 8,000. The location of these peptides in the intact protein was determined by analysis of partial cleavage products. The 8,000 Mr peptide (CB2) was found to be located in the central region of the protein. Chymotrypsin cleavage of protein IB revealed a cleavage site near one of the cyanogen bromide cleavage sites. Trypsin was found to cleave the protein, either in outer membranes complexes (OMC) or in detergent micelles, in the central CB2 fragment. These results suggest that CB2 is a part of the surface-exposed region of protein IB. Immunization of mice with purified protein IB (serotype 5) induced antibodies against all three CB-peptides. Absorption of the sera with homologous OMC resulted in a complete removal of antibodies against CB2, supplying further evidence for its surface-exposed nature. Antibodies against the 13,000 Mr peptide (CB1) could not be absorbed with intact OMC, suggesting that this peptide is buried within the outer membrane. Antisera raised against CB2 of serotype 5 demonstrated a considerable cross-reactivity with heterologous outer membranes. On the contrary, intact OMC induced mainly type-specific antibodies. These data demonstrate the presence of conserved epitopes on the surface-exposed CB2 peptide. These conserved epitopes are generally not very immunogenic when present in intact OMC.

O-polysaccharide-protein conjugates induce high levels of specific antibodies to Pseudomonas aeruginosa immunotype 3 lipopolysaccharide

A semi-synthetic vaccine against Pseudomonas aeruginosa immunotype 3 was prepared by chemical coupling of P. aeruginosa immunotype 3 O-polysaccharide to tetanus toxoid. The O-polysaccharide was obtained by mild acid hydrolysis of immunotype 3 lipopolysaccharide, and purified by gel permeation chromatography. The purification was evaluated by high performance liquid chromatography. Additional analyses revealed a high grade of purity of the O-polysaccharide, and an at least 1000-fold reduction of endotoxic activity as compared to homologous lipopolysaccharide. O-Polysaccharide was conjugated to tetanus toxoid, using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as coupling reagent. Antigenic determinants of both O-polysaccharide and tetanus toxoid were retained after conjugation, as tested in a sandwich enzyme-linked immunosorbent assay. Immunization of mice revealed that O-polysaccharide was nonimmunogenic in mice, while the O-specific part of the conjugate was able to induce high levels of IgG antibodies reacting with immunotype 3 lipopolysaccharide in an enzyme-linked immunosorbent assay. By immunoblotting it was shown that the antibodies were directed to high molecular weight lipopolysaccharide only, demonstrating specificity for its O-polysaccharide moiety.

Cloning and nucleotide sequence of heavy- and light-chain cDNAs from a creatine-kinase-specific monoclonal antibody

Determination of creatine kinase isoenzymes by inhibition assay is a useful tool for the diagnosis and monitoring of myocardial infarction. We have established several mouse hybridoma lines secreting monoclonal antibodies with creatine kinase M-subunit inhibitory capacity. One of the monoclonal antibodies (MAK33) inhibits creatine kinase-MM by 80% without influencing the activity of creatine kinase-MB. A combination of two monoclonal antibodies increased the inhibition of creatine kinase MM up to 99.4%. Poly(A) + RNA of hybridoma cells secreting MAK33 was isolated and used for cloning cDNA of both heavy and light chains of this antibody. Full-length cDNA clones were obtained by hybridization with gamma 1 and kappa constant region cDNA probes. The complete nucleotide sequences from the variable regions including signal peptide and part of the 5'-untranslated regions have been determined.

The kinase C substrate protein B-50 and axonal regeneration

As reported previously the prominent protein kinase C substrate protein B-50 is present in growth cones isolated from fetal rat brain and in outgrowing hippocampal neurites. These findings suggest that B-50 plays a role in axonal growth during development of the nervous system. In the present paper the fate of B-50 is investigated in regenerating rat sciatic nerve. Using affinity-purified anti-B-50 antibodies B-50 levels have been compared in crushed and contralateral intact nerves by means of immunoblotting and radioimmunoassay. B-50 levels in the crushed nerve increased 5.3-fold as compared to non-crushed controls. Furthermore, the cellular localization of B-50 has been assessed by immunohistochemistry. Virtually no B-50 immunoreactivity was seen in control nerves, but bright immunofluorescence appeared in regenerating sprouts. Our data are in line with current evidence from several laboratories that B-50 is a member of a small family of growth-associated proteins and support the hypothesis that B-50 is involved in axonal growth.

Nerve growth factor enhances the level of the protein kinase C substrate B-50 in pheochromocytoma PC12 cells

Exposure of PC12 cells to nerve growth factor results in arrest of cell growth and induction of differentiation to sympathetic neuron-like cells, bearing neurites. In this study we identify a 48 kDa PC12 phosphoprotein as the neuron-specific protein kinase C substrate B-50 (Mr 48 kDa; IEP 4.5) on basis of comigration with purified B-50, immunoreactivity and phosphopeptide mapping. B-50 is present in both undifferentiated and differentiated PC12 cells. Exposure of PC12 cells to nerve growth factor for two days results in a 2.5-fold increase in the amount of B-50 as measured by RIA. Indirect immunofluorescence microscopy reveals that B-50 is mainly localized at the cell membrane and in growth cones. Our data are in line with the hypothesis that B-50 plays a role in neurite outgrowth and indicate that PC12 cells provide a suitable model to study this hypothesis.

Expression of biosynthetic genes from Pseudomonas aeruginosa and Escherichia coli in the heterologous host

We examine the expression of constitutive or repressible, monocistronic genes from Pseudomonas aeruginosa and Escherichia coli after their transfer to the heterologous host. To this end, chromosomal DNA from P. aeruginosa was cloned into the mobilizable broad-host-range vector pKT240; recombinant plasmids carrying the argA, argF, or proC genes were identified by complementation of the corresponding auxotrophic mutations. The isofunctional E. coli genes and the E. coli proB gene were subcloned into pKT240 from existing recombinant plasmids. The enzyme expression specified by the Pseudomonas genes in E. coli, calculated per gene copy, ranged from 0.3%-5% of the levels observed in Pseudomonas. Fusion of the P. aeruginosa proC gene to the E. coli consensus tac promoter resulted in very high proC enzyme production in E. coli, indicating that, at least in this case, the expression barrier is essentially at the level of transcriptional initiation. The E. coli argA and argF enzymes, which are controlled by repression in their native host, were synthesized constitutively in P. aeruginosa at 5% of the levels measured in E. coli under derepressed conditions. The constitutive E. coli proB and proC genes were expressed at high levels (ca. 50%) in the heterologous host. These results support the idea that P. aeruginosa may be a more permissive host than E. coli for the heterologous expression of genes from gram-negative bacteria.

Expression of the Pseudomonas aeruginosa PAK pilin gene in Escherichia coli

Pseudomonas aeruginosa is a piliated opportunistic pathogen. We have recently reported the cloning of the structural gene for the pilus protein, pilin, from P. aeruginosa PAK (B. L. Pasloske, B. B. Finlay, and W. Paranchych, FEBS Lett. 183:408-412, 1985), and in this paper we present evidence that this chimera (pBP001) expresses P. aeruginosa PAK pilin in Escherichia coli independent of a vector promoter. The strength of the promoter for the PAK pilin gene was assayed, and the cellular location of the pilin protein within E. coli was examined. This protein was present mainly in the inner membrane fraction both with and without its six-amino-acid leader sequence, but it was not assembled into pili.

In situ enzyme immunodetection of surface or intracellular bacterial antigens using nitrocellulose sheets

We describe an immunological method which allows the in situ colorimetric detection of translated DNA fragments in bacteria. In the absence of lysis only cell surface proteins are detected. For cytoplasmic proteins, lysis is required. The procedure comprises the following steps: bacteria are lysed, the proteins are transferred onto a disc of nitrocellulose sheet, the remaining protein sites are blocked, the disc is successively soaked in a solution of antibodies specific for the protein to be detected and in a solution of peroxidase-labelled anti-IgG antibody solution. Finally, the immune complexes are made visible by enzyme substrate incubation. We describe the application of this method to the detection of the LamB protein, the LacZ protein, and a LamB-polio VP1 chimera translated from cloned DNA fragment in E. coli.

Molecular cloning and structure of the gene for 7 beta-(4-carboxybutanamido)cephalosporanic acid acylase from a Pseudomonas strain

A Pseudomonas strain produced an enzyme capable of deacylating 7 beta-(4-carboxybutanamido)cephalosporanic acid to 7-aminocephalosporanic acid in response to glutaric acid. The gene for the enzyme was cloned within the PstI site of pBR325 as a 7.35-kilobase-pair DNA segment from a mutant of this strain whose enzyme is produced constitutively. The gene expression in the primary clone appeared to be low in Escherichia coli but was significantly enhanced by reducing the size of the initial segment coupled with E. coli promoters. Subsequent subcloning resulted in localization of the gene to a 2.45-kilobase-pair fragment. Three clone-specific polypeptides with molecular weights of ca. 16,000, 54,000, and 70,000 were shown by maxicell analysis. The former two corresponded to the small and large subunits of the purified enzyme from the Pseudomonas strain, and the third polypeptide was suggested to be their precursor. This was supported by DNA sequence study together with amino acid sequencing of the amino terminus of both subunits: the sequences for the small and large subunits were localized contiguously in this order on the structural gene without termination codons between them. The nucleotide sequence also disclosed the presence of a signallike sequence preceding that for the small subunit, consistent with the previous observation that the enzyme might be periplasmic in the Pseudomonas strain. Those results suggest a process for the formation of an active enzyme complex from a precursor through two steps of processing.

Multiple phosphorylation of pp30, a rat brain polyribosomal protein, sensitive to polyamines and corticotropin

A rat brain polyribosomal protein with an apparent Mr of 30 000, designated pp30, was further characterized. The protein was identified by its phosphorylation by an endogenous protein kinase sensitive to both corticotropin and spermine. Two-dimensional separation of a polyribosomal fraction was applied, combining non-equilibrium pH-gradient-gel electrophoresis in the first and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis in the second dimension. In this system, pp30 was separated into at least five defined phosphoprotein spots. Pulse-labelling with [gamma-32P]ATP followed by a chase for various time periods with excess unlabelled ATP resulted in a shift of the distribution of radioactivity and protein staining along the spots towards the anode. This suggests that the various spots of pp30 may represent multiple phosphorylation states. Limited proteolysis of the five spots with three different proteinases resulted in the same one-dimensional peptide maps with a given proteinase, indicating that all five spots represent different forms of a single phosphoprotein. Inhibition of the overall phosphorylation of pp30 by corticotropin or spermine was accompanied by a shift in the recovery of labelled phosphate towards spots nearer the cathode. Immunoblotting with monoclonal antibodies directed against ribosomal protein S6 stained only one band, a protein that had an apparent Mr of 34 000 and was clearly distinct from pp30.

Molecular cloning of the Pseudomonas carboxypeptidase G2 gene and its expression in Escherichia coli and Pseudomonas putida

The gene coding for carboxypeptidase G2 was cloned from Pseudomonas sp. strain RS-16 into Escherichia coli W5445 by inserting Sau3A-generated DNA fragments into the BamHI site of pBR322. The plasmid isolated, pNM1, was restriction mapped, and the position of the gene on the 5.8-megadalton insert was pinpointed by subcloning. The expression of carboxypeptidase in E. coli was 100-fold lower than in the Pseudomonas sp. strain. When the cloned gene was subcloned into the Pseudomonas vector pKT230 and introduced into Pseudomonas putida 2440, a 30-fold increase in expression over that obtained in E. coli was observed. High expression (up to 5% soluble protein) was obtained in E. coli by subcloning a 3.1-megadalton Bg/II fragment into the BamHI site of pAT153. The increased expression was orientation dependent and is presumed to be due to transcriptional readthrough from the Tc promoter of the vector. Production of carboxypeptidase was shown to be induced (two-fold) by the presence of folic acid, and the mature protein was shown to be located in the periplasmic space of E. coli.

Molecular cloning and expression of Treponema pallidum DNA in Escherichia coli K-12

A gene bank of Treponema pallidum DNA in Escherichia coli K-12 was constructed by cloning SauI-cleaved T. pallidum DNA into the cosmid pHC79. Sixteen of 800 clones investigated produced one or more antigens that reacted with antibodies from syphilitic patients. According to the separation pattern of the antigens produced on sodium dodecyl sulfate-polyacrylamide gels, six different phenotypes were distinguished among these 16 clones. These antigens reacted also with anti-T. pallidum rabbit serum. No antibodies against the cloned antigens were found in normal rabbit serum and in nonsyphilitic human serum. The antigens produced by the E. coli K-12 recombinant DNA clones comigrated in sodium dodecyl sulfate-polyacrylamide gels with antigens extracted from T. pallidum bacteria, suggesting that the treponemal DNA is well expressed in E. coli K-12. Several of the cosmid recombinant plasmids have been subcloned, resulting in smaller T. pallidum recombinant plasmids which are more stably maintained in the cell and produce more treponemal antigen. Monoclonal antibodies were raised against T. pallidum, and one hybridoma produced antibodies that reacted not only with an antigen from T. pallidum but also with the antigen produced by one of the E. coli clones.

Characterization of the phospholipase C gene of Pseudomonas aeruginosa cloned in Escherichia coli

We have cloned a 4.9-kb fragment of Pseudomonas aeruginosa DNA containing the structural gene of phospholipase C (PLC), by inserting it into the BamHI site of plasmid pBR322. Strains of Escherichia coli carrying this recombinant plasmid produce PLC, but expression of the gene differs from that in P. aeruginosa in two respects: (i) synthesis of the enzyme appears to be constitutive, i.e., not repressible by the presence of inorganic phosphate in the growth medium, and (ii) most of the enzyme remains associated with the outer membrane instead of being secreted. Insertion mutagenesis at a unique restriction site within the PLC gene destroyed the ability of the plasmid to code, in maxicells, for phospholipase C activity and for an Mr 80000 polypeptide.