Identification of promoter and stringent regulation of transcription of the fabH, fabD and fabG genes encoding fatty acid biosynthetic enzymes of Escherichia coli.

In Escherichia coli, amino acid starvation results in the coordinate inhibition of a variety of metabolic activities, including fatty acid and phospholipid biosynthesis. By using primer extension analysis we identified the fabH promoter responsible for transcription of the fabH, fabD and fabG genes encoding fatty acid biosynthetic enzymes. The response of the fabH promoter to amino acid starvation was determined in vivo. Transcripts originating from the fabH promoter were quantified by employing a ribonuclease protection assay. The fabH promoter was subject to relA-dependent stringent control and was repressed approximately 4-fold upon amino acid starvation. The results suggest that inhibition of transcription initiation of lipid biosynthetic genes in starved cells contributes to the stringent control of lipid biosynthesis.

Lipid biosynthetic genes and a ribosomal protein gene are cotranscribed.

By using insertional mutagenesis we demonstrated that the rpmF gene encoding ribosomal protein L32, the plsX gene encoding a protein involved in membrane lipid synthesis and several fatty acid biosynthetic genes (fabH, fabD and fabG) are cotranscribed. Organization of these genes into an operon may play a role in the coordinate regulation of the synthesis of ribosomes and the cell membranes.

A new vector-host system for construction of lacZ transcriptional fusions where only low-level gene expression is desirable.

We improved a multicopy vector, pRS415 [Simons et al., Gene 53 (1987) 85-96], for use in operon fusion constructions by introducing a new multiple cloning site (MCS) containing eight unique restriction sites upstream from the promoterless reporter gene lacZ. In order to reduce plasmid copy number, a new Escherichia coli strain SP2 (pcnB, delta lac, recA) was constructed. This strain permits analysis of fusions in cases where high gene dosage may be detrimental.

Cloning and sequencing of the Thermoanaerobacterium saccharolyticum B6A-RI apu gene and purification and characterization of the amylopullulanase from Escherichia coli.

The amylopullulanase gene (apu) of the thermophilic anaerobic bacterium Thermoanaerobacterium saccharolyticum B6A-RI was cloned into Escherichia coli. The complete nucleotide sequence of the gene was determined. It encoded a protein consisting of 1,288 amino acids with a signal peptide of 35 amino acids. The enzyme purified from E. coli was a monomer with an M(r) of 142,000 +/- 2,000 and had same the catalytic and thermal characteristics as the native glycoprotein from T. saccharolyticum B6A. Linear alignment and the hydrophobic cluster analysis were used to compare this amylopullulanase with other amylolytic enzymes. Both methods revealed strictly conserved amino acid residues among these enzymes, and it is proposed that Asp-594, Asp-700, and Glu-623 are a putative catalytic triad of the T. saccharolyticum B6A-RI amylopullulanase.

Sequencing of the amylopullulanase (apu) gene of Thermoanaerobacter ethanolicus 39E, and identification of the active site by site-directed mutagenesis.

The complete nucleotide sequence of the gene encoding the dual active amylopullulanase of Thermoanaerobacter ethanolicus 39E (formerly Clostridium thermohydrosulfuricum) was determined. The structural gene (apu) contained a single open reading frame 4443 base pairs in length, corresponding to 1481 amino acids, with an estimated molecular weight of 162,780. Analysis of the deduced sequence of apu with sequences of alpha-amylases and alpha-1,6 debranching enzymes enabled the identification of four conserved regions putatively involved in substrate binding and in catalysis. The conserved regions were localized within a 2.9-kilobase pair gene fragment, which encoded a M(r) 100,000 protein that maintained the dual activities and thermostability of the native enzyme. The catalytic residues of amylopullulanase were tentatively identified by using hydrophobic cluster analysis for comparison of amino acid sequences of amylopullulanase and other amylolytic enzymes. Asp597, Glu626, and Asp703 were individually modified to their respective amide form, or the alternate acid form, and in all cases both alpha-amylase and pullulanase activities were lost, suggesting the possible involvement of 3 residues in a catalytic triad, and the presence of a putative single catalytic site within the enzyme. These findings substantiate amylopullulanase as a new type of amylosaccharidase.

Analysis of the catalytic center of cyclomaltodextrinase from Thermoanaerobacter ethanolicus 39E.

The amino acid sequences of cyclomaltodextrinase (CDase) from Thermoanaerobacter ethanolicus 39E (formerly Clostridium thermohydrosulfuricum 39E) and other amylolytic enzymes were compared by using linear alignment and hydrophobic cluster analysis. Two Asp and one Glu residue, which were considered to be the catalytic residues of the compared enzymes according to crystallographic or protein engineering experiments, were also conserved in CDase. Asp325, Asp421 and Glu354 of the CDase were individually replaced by means of site-directed mutagenesis. The mutant enzymes completely lost activity, suggesting that these residues play an important role in catalysis.

Purification and characterization of phosphoenolpyruvate carboxykinase,a catabolic CO2-fixing enzyme, from Anaerobiospirillum succiniciproducens.

Phosphoenolpyruvate (PEP) carboxykinase (EC 4.1.1.49) from the obligate anaerobe Anaerobiospirillum succiniciproducens was purified 18-fold. The enzyme was monomeric, with an Mr of 57,000 +/- 2,000. The enzyme was oxygen stable, had a pH optimum of 6.7-7.1, and was stable from pH 5.0 to 9.0. The enzyme displayed Michaelis-Menten kinetics for the substrate PEP and the cosubstrates bicarbonate and ADP with a Km of 0.54 mM, 17 mM and 0.42 mM, respectively. The enzyme required Mn(2+) or Co(2+) in addition to Mg(2+) to exhibit maximum activity. p-Chloromercuribenzoate inhibited activity and phosphoenolpyruvate protected the enzyme against inactivation, suggesting that an essential cysteine may be in the active site.

Structure of the gene encoding cyclomaltodextrinase from Clostridium thermohydrosulfuricum 39E and characterization of the enzyme purified from Escherichia coli.

Clostridium thermohydrosulfuricum 39E, a gram-positive thermophilic anaerobic bacterium, produced a cyclodextrin (CD)-degrading enzyme, cyclodextrinase (CDase) (EC 3.2.1.54). The enzyme was purified to homogeneity from Escherichia coli cells carrying a recombinant multicopy plasmid that contained the gene encoding for thermophilic CDase. The purified enzyme was a monomer with an M(r) of 66,000 +/- 2,000. It showed the highest activity at pH 5.9 and 65 degrees C. The enzyme hydrolyzed alpha-, beta-, and gamma-CD and linear maltooligosaccharides to yield maltose and glucose. The Km values for alpha-, beta-, and gamma-CD were 2.5, 2.1, and 1.3 mM, respectively. The rates of hydrolysis for polysaccharides (starch, amylose, amylopectin, and pullulan) were less than 5% of the rate of hydrolysis for alpha-CD. The entire nucleotide sequence of the CDase gene was determined. The deduced amino acid sequence of CDase, consisting of 574 amino acids, showed some similarities with those of various amylolytic enzymes.

[Cloning and expression of the gene for thermostable pullulanase from Clostridium thermohydrosulfuricum in Escherichia coli]. / Klonirovanie i ékspressiia gena termostabil'noi pullulanazy Clostridium thermohydrosulfuricum v kletkakh Escherichia coli.

Using a pUC19-based genomic library of the anaerobic thermophilic bacterium C. thermohydrosulfuricum a DNA fragment that confers pullulanase activity to E. coli cells has been identified. Subcloning and restriction mapping procedures was carried out and the primary structure of the 5'-region of the pullulanase gene (pul) was determined. The pul enzyme was shown to be a protein with molecular weight of approximately 60,000. It was found that both pullulanase and glucoamylase activities resides in pullulanase. The intracellular distribution of pullulanase was studied. An E. coli strain that produces large amounts of thermostable pullulanase has been constructed.

[Isolation and characteristics of thermostable pullulanase from Clostridium thermohydrosulfuricum produced by Escherichia coli cells]. / Vydelenie i kharakteristika termostabil'noi pullulanazy Clostridium thermohydrosulfuricum, produtsiruemoi kletkami Escherichia coli.

The expressed gene (pul) for a thermostable pullulanase from Clostridium thermohydrosulfuricum was cloned into Escherichia coli. The enzyme was purified from cell extracts of E. coli by thermoinactivation, ammonium sulphate precipitation and gel exclusion. The purified enzyme was characterized as monomer with both pullulanase and glucoamylase activities. The general physico-chemical and catalytic properties of this enzyme were obtained. In particular, pullulanase and glucoamylase activities were stable and optimally active at 65 degrees C. The pH optimum for activity was 5.8. The amino acid composition and amino acid sequence of N-terminal end were estimated.

Expression of the hAng gene in Escherichia coli; isolation and characterization of human recombinant Ser-(-1) angiogenin.

Recombinant human angiogenin has been synthesized in Escherichia coli with the aid of a human angiogenin gene (hAng) cloned by Neznanov et al (1990) from a human complementary DNA (cDNA) library. The gene has been expressed by use of a new type of expression vector called a 'TGATG vector' (plasmid pPR-TGATG-1; Mashko et al 1990a). The highest level of accumulation of the recombinant angiogenin (6%-8% of the total cell protein) was observed in E. coli strain BL21 carrying a temperature-amplifiable version of the plasmid. The synthesized polypeptide carries an additional serine residue at its N terminus in comparison with natural angiogenin. Furthermore, the initiator methionine residue of the recombinant protein is removed with high efficiency by E. coli terminal aminopeptidase. Simple procedures for purification of the recombinant angiogenin from the insoluble fraction of cell protein, and for refolding the protein allowed the isolation of almost 5 mg recombinant angiogenin g-1 wet bacterial biomass. The recombinant Ser-(-1) angiogenin displayed the same biological properties (specific RNAase activity and the ability to induce blood vessel growth on the sclera of experimental animals) as its natural counterpart isolated from human blood.

[Creation of artificial hybrid operons with partially overlapping genes to achieve an expression of heterologous genes in Escherichia coli cells]. / Sozdanie "iskusstvennykh gibridnykh operonov s chastichno perekryvaiushchimisia genami" dlia dostizheniia ékspressii geterologichnykh genov v kletkakh Escherichia coli.

A new method of optimization of foreign gene expression in E. coli, based on the construction of hybrid operons with partially overlapping genes is described. The partial overlapping of the translation termination and initiation sites in the formed operon must provide translational coupling of appropriate gene product synthesis. Such an approach has provided the synthesis of human interferon alpha F in E. coli cells under the control of the lacUV5-promotor up to about (3-4).10(7) units per liter of bacterial culture. The reinitiation of the distal gene translation is shown to take place in the intercistronic region. Substitution of the lacUV5 promotor by the more efficient tac one allowed to increase the synthesis level of interferon alpha F to (1-2).10(8) units per liter. The conclusion is made about the equimolarity of distal and proximal to the promotor genes products syntheses when the intercistronic region of E. coli trpE-trpD genes are used for translational coupling.

[Optimization of the gene expression for human alpha F- and beta 1-interferons in Escherichia coli cells]. / Optimizatsiia ékspressii genov al'fa F- i beta 1-interferonov v kletkakh Escherichia coli.

The basic results of the studies on expression of the genes of human alpha F- and beta 1-interferons in E. coli cells are presented. To synthesize the fibroblast interferon, the respective fragment of the human chromosome was cloned, the complete nucleotide sequence of the structural moiety of mature beta-interferon was determined and the genes of "hybrid (interferon-like) proteins" and "hybrid sites of ribosome binding" were constructed with control of the beta-interferon gene by the prokaryotic regulatory areas. Synthesis of beta-interferon was achieved (1.10(7)-5.10(7) IU per 1 l of the bacterial culture) with the use of the tryptophan operon promoter. A new procedure for optimization of allogenic genetic information in E. coli cells: constructing of "hybrid operons with partially overlapping genes" or artificial "overlappons" was developed following the example of the alpha F-interferon gene cloned in the Laboratory headed by E. D. Sverdlov at the Institute of Bioorganic Chemistry of the USSR Academy of Sciences. The use of this procedure enabled production of up to 5.10(7) IU/l of alpha F-interferon under the control of the lacUV5-promoter. On the basis of the newly constructed vector molecules expression of the genes of alpha F- and beta 1-interferons was amplified with the "overlappon" procedure.

[Effectiveness of expression of the chloramphenicol acetyltransferase gene controlled by foreign regulator regions in Escherichia coli cells. II. Molecular cloning of promoters]. / Issledovanie éffektivnosti ékspressii gena khloramfenikolatsetiltransferazy pod kontrolem chuzherodnykh reguliatornykh oblastei v kletkakh Escherichia coli. II. Molekuliarnoe klonirovanie promotorov.

The trpOP, lacUV5, tacOP, PR and PL-promotors were cloned in the previously obtained pML4 vector plasmid. The expression of structural gene cat was studied by the chloramphenicolacetyltransferase determination in cell extracts. The level of protein synthesis by appropriate recombinant plasmids was analysed in vivo and in vitro. It was shown that the efficiency of the gene expression is determined by both the "strength" of the promotors and mRNA translation specificity. The obtained collection of the plasmids might be used for the determination of the promotor strength by the hybridization of pulse-labeled mRNA with DNA and an effective expression of the genes by means of "hybrid protein gene" and "hybrid operon" constructions.

[Expression of the chloramphenicol acetyltransferase gene is under control of various promoters of E. coli and phage lambda]. / Ekspressiia gena khloramfenikolatsetiltransferazy pod kontrolem nekotorykh promotorov E. coli i bakteriofaga lambda.

Plasmids have been constructed with the structural region of the cat gene being under the control of the lactose (lacUV5), tryptophane (trpOP), operons of Escherichia coli, the hybrid trp-lac (tac) promoter and early bacteriophage lambda promoters (PL, PR and PLIT). The expression of chloramphenicolacetyltransferase gene in Escherichia coli cells harbouring such recombinant plasmids and pBR325 as well has been examined by determining the chloramphenicol resistance and studying the enzyme activity of Cm-acetylase. A high level of enzyme synthesis is connected with transcription from PL, PR and tac promoters.

[Effectiveness of expression of the chloramphenicol acetyltransferase gene controlled by foreign regulatory regions in Escherichia coli cells. I. Construction of vectors for the cloning of transcription regulatory elements]. / Issledovanie éffektivnosti ékspressii gena khloramfenikolatsetiltransferazy pod kontrolem chuzherodnykh reguliatornykh oblastei v kletkakh Escherichia coli. I. Konstruirovanie vektorov dlia klonirovaniia reguliatornykh élementov transkriptsii.

New plasmids pML2.1 and pML4 were constructed for cloning the transcription regulatory regions. In the pML2.1 the structural part of chloramphenicol acetyltransferase gene of the pBR325 is under control of the lacUV5-promotor. Because the unique BamH1 cleavage site is in the joint region, one may use it for cloning transcription termination regions and selecting recombinant clones with the AprCms phenotype. As for the pML4, the foreign fragment integration is carried directly before the structural part of cat-gene and it is expressed only if the promotor regions are present. The plasmids were sequenced and their restriction maps were established. Small molecular weight (about 2,0 MDa, AprCmr) or only Apr intact genes and convenient disposition of many unique cleavage sites by restriction endonucleases make these plasmids useful for different genetic engineering experiments.