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  • 1
    ISSN: 1617-4623
    Keywords: pepD gene ; gpt gene ; Intergenic region ; lpcA locus ; Peptidase D purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cloned DNA fragment, carrying the gene for peptidase D (pepD) of Escherichia coli, was partially sequenced. By purification of peptidase D and sequence determination of an amino-terminal oligopeptide the reading frame of the pepD gene, starting with a GTG initiator codon, was unambiguously identified. An overlap of the established nucleotide sequence with the previously sequenced 5′ flanking region of the gpt gene allowed the exact distance between pepD and gpt to be calculated. The two genes are pointing towards each other and are separated by 260 bp. A search for open reading frames (ORFs) and the analysis of possible codon usage in the intercistronic region indicate the absence of an additional gene (lpcA) between pepD and gpt.
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  • 2
    ISSN: 1617-4623
    Keywords: envCD operon ; Nucleotide sequence ; EnvC protein ; Membrane localization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The chromosomal DNA insert in plasmid pJK131, which complements the phenotypic defects associated with a mutation in the envC gene of Escherichia coli strain PM61, was sequenced. The analysis of the nucleotide sequence revealed two open reading frames (ORFs) coding for the proteins EnvC (41281 daltons) and EnvD (104415 daltons). The envC gene product is synthesized as a pre-protein and, after cleavage of a signal peptide, the mature protein is incorporated into the cytoplasmic membrane. The detection of a common transcript for both ORFs indicated the existence of an envCD operon. Deletion analysis and the generation of frameshifts demonstrated that simultaneous expression of both genes is required to complement the defects in strain PM61. Overproduction of EnvC protein appears to be lethal to Escherichia coli. The envD gene, however, could be cloned and expressed at high levels under control of the tac promotor without deleterious effects on the host.
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  • 3
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract DNA fragments complementing theenvC mutation could be isolated by cloning chromosomal DNA in the vector pUH84. When the frequencies of transformation and the frequencies of restoring theenvC + phenotype were compared, the high copy number hybrid plasmids complemented with a frequency of 10−5. After subcloning theenvC-complementing DNA fragment into the low copy number plasmid pLG339, efficient complementation was achieved by spontaneous integration of the IS2 element ofEscherichia coli. By nucleotide sequence analysis, a potential promoter, a ribosome-binding site, and an unidentified reading frame were detected in the respective DNA fragment.
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  • 4
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract InEscherichia coli C infected with bacteriophage ϕX174, the cytoplasmic and outer membranes of the host bacterium exhibit various alterations in their protein composition as revealed by sodium dodecyl sulfate gel electrophoresis of purified membranes. These alterations result mainly from the action of the lysis gene product of the phage. One effect of the changes occurring in the membranes results in different rates of release of wild-type phage and its lysis-negative mutant from glycine spheroplasts. The activity of phospho-MurNAc-pentapeptide translocase, an enzyme involved in murein synthesis and located in the cytoplasmic membrane, is unimpaired by these alterations.
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  • 5
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The lytic effect of the expression of the cloned geneE of bacteriophage ϕX174 inEscherichia coli is considerably amplified by a mutation in thefadR gene, which primarily affects the regulation of fatty acid degradation. In contrast, reduction of the fluidity of the cell membranes by use of thefabB andfadE mutations, which interfere with the synthesis and the oxidation of unsaturated fatty acids, severely inhibits the action of the ϕX174 lysis gene product. A chain-forming mutant carrying a pleiotropic mutation in theenvC locus is also refractory to the ϕX174 lysis protein. As shown by reversion and complementation of theenvC mutatation, a defect in at least one additional gene (rle) is involved in the generation of this refractoriness.
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  • 6
    ISSN: 1617-4623
    Keywords: Peptidase D ; pepD promoter ; Deletion analysis ; Phosphate limitation ; pepD regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of deletions removing progressively larger parts of the 5′ flanking region of the Escherichia coli pepD gene was constructed. After fusing the resulting promoter fragments to the chromosomal malPQ operon, their activities were determined by assaying for amylomaltase, the product of the malQ gene. Transcription from the pepD promoter region in exponentially growing cells was estimated to be about 5 times less efficient than transcription from the induced lac promoter. Approximately 115 by preceding the translation start site of the pepD gene are important for regular promoter functioning, whereas the more distal sequences could be deleted without any significant effects. In bacterial cultures containing limiting amounts of inorganic phosphate, the rate of de novo synthesis of peptidase D, simultaneously with the derepression of alkaline phosphatase, increased about fivefold as a consequence of phosphate starvation. This regulation was shown to occur at the transcriptional level by the use of chromosomal pepD promoter-malPQ fusions. The inducibility by phosphate limitation was conserved in all of the deletion clones in which the pepD promoter region was still functional. As demonstrated by the use of phoB, R, and M mutants, the modulation of pepD expression is independent of the genetic system controlling the pho regulon.
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  • 7
    ISSN: 1617-4623
    Keywords: Branched-chain amino acid transport ; Lactobacillus delbrückii subsp. lactis ; Nucleotide sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A gene (brnQ), encoding a carrier for branched-chain amino acids in Lactobacillus delbrückii subsp. lactis DSM7290 was cloned in the low-copy-number vector pLG339 by complementation of a transport-deficient Escherichia coli strain. The plasmid carrying the cloned gene restored growth of an E. coli strain mutated in 4 different branched-chain amino acid transport genes at low concentrations of isoleucine, and increased its sensitivity to valine. Transport assays showed that leucine, isoleucine and valine are transported by this carrier and that transport is driven by the proton motive force. Nucleotide sequence analysis revealed an open reading frame of 1338 bp encoding a hydrophobic protein of 446 amino acids with a calculated molecular mass of 47864 Daltons. The start site of brnQ transcription was determined by primer extension analysis using mRNA from Lactobacillus delbrückii subsp. lactis DSM7290. The hydropathy profile suggests the existence of at least 12 hydrophobic domains that probably form membrane-associated α-helices. Comparisons of the nucleotide sequence of brnQ from Lactobacillus delbrückii subsp. lactis DSM7290, the amino acid sequence of its product and the topology of the hydrophobic domains with those of the respective carrier genes and proteins of Salmonella typhimurium and Pseudomonas aeruginosa revealed extensive homology.
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  • 8
    ISSN: 1617-4623
    Keywords: Prolidase ; Metalloprotease ; Lactobacillus delbrueckii subsp. lactis ; Nucleotide sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From a genomic library of Lactobacillus delbrueckii subsp. lactis (DSM7290) DNA, in the low-copy-number vector pLG339, a recombinant clone was selected, which complemented a mutation in the prolidase gene (pepQ) of Escherichia coli UK173. Nucleotide sequence analysis revealed an open reading frame of 1104 nucleotides corresponding to a protein of 368 amino acids with a calculated pI of 4.64 and a molecular mass of 41087 Da. The start site of pepQ transcription was determined by primer extension analysis with mRNA prepared from L. delbrueckii. Based on homology of the gene product to various peptidases and on the substrate specificity determined, the peptidase was designated PepQ. The influence of various protease inhibitors and cations on peptidase activity indicated that PepQ is a metalloprotease. The absence of a membrane-spanning domain and a signal peptide sequence argues for a cytoplasmic localization of the enzyme.
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  • 9
    ISSN: 1432-072X
    Keywords: Escherichia coli ; d-phenylglycine ; Peptide utilization ; Transport mutants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Escherichia coli K 12 is able to utilize the dipeptide d-phenylglycyl-glycine as a source of glycine. Growth experiments with a glycine auxotrophic mutant show that utilization of the dipeptide is competitively inhibited by d-alanine at a K iof 4×10-4 M. In contrast, l-alanyl-l-alanine which is transported via the system specific for dipeptides does not interfere with the utilization of d-phenylglycyl-glycine. This indicates that the dipeptide is hydrolyzed prior to uptake, and d-alanine therefore competes with the uptake of glycine via the transport system common for both amino acids. This was confirmed by examining the growth response of various transport mutants. A mutant deficient in the transport of oligo- and dipeptides grows as well as the wild type on d-phenylglycyl-glycine, whereas the growth of mutants deficient in the transport of glycine is severely impaired or prevented with this dipeptide. It is therefore demonstrated that d-phenylglycyl-glycine is hydrolyzed prior to uptake. This is a mechanism of peptide utilization in E. coli K 12 which is distinct from that described so far for other dipeptides.
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  • 10
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Summary The influence of penicillin on the concentration of nucleotide-activated mucopolymer precursors was studied in Proteus mirabilis and in its unstable L-form. Cell extracts were chromatographed on Dowex-1, and some of the nucleotides were characterized. 1. During the penicillin-induced transition of cells of P. mirabilis to spheroplasts no accumulation of UDP-activated mucopolymer precursors was observed. Only the concentration of UMP decreases during the formation of spheroplasts. 2. In P. mirabilis and in its spheroplasts small amounts of mucopolymer precursors were detected their concentration being not higher in spheroplasts than in rod-shaped cells of P. mirabilis. 3. The unstable, mucopolymer-containing L-form I Ca, derived from P. mirabilis by use of penicillin, contains approximately the same amount of mucopolymer precursors as rod-shaped cells of P. mirabilis. The concentration of cytidine nucleotides was many times higher in the L-form than in P. mirabilis.
    Notes: Zusammenfassung Es wurde der Einfluß von Penicillin auf die Konzentrationen der freien Nucleotide in Proteus mirabilis D52 und in dessen instabiler L-Phase untersucht. Zellextrakte wurden an Dowex-1 chromatographiert und ein Teil der dabei isolierten Nucleotide charakterisiert. 1. Mit der durch Penicillin verursachten Umwandlung stäbchenförmiger Proteus-Bakterien in Sphäroplasten ist keine Anreicherung UDP-aktivierter Mucopolymervorstufen verbunden. Lediglich die Konzentration von UMP nimmt dabei stark ab. 2. Sowohl in Proteus D 52 als auch in penicillininduzierten Sphäroplasten von Proteus D 52 konnten geringe Mengen von UDP-aktivierten Mucopolymervorstufen nachgewiesen werden; ihre Konzentration ist in Sphäroplasten nicht höher als in stäbchenförmigen Zellen von Proteus D 52. 3. Die instabile, mucopolymerhaltige L-Phase I Ca von P. mirabilis D 52 weist gegenüber Proleus D 52 und penicillininduzierten Sphäroplasten von Proteus D 52 einen vielfach höheren Gehalt an Cytidinnucleotiden auf. Der Gehalt an Mucopolymervorstufen ist praktisch gleich. Es wird daher angenommen, daß Penicillin die morphologischen Änderungen, z. B. die Bildung von Sphäroplasten und instabilen l-Formen von P. mirabilis nicht durch die Hemmung der Polymerisation UDP-aktivierter Vorstufen verursacht, sondern durch die Hemmung späterer Schritte der Zellwandsynthese wie z. B. die Verbindung des Mucopolymers mit Lipoprotein.
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