PubMed Health⌕ Search

Biomedical subjects

F Imamoto

Publications and source records attributed to F Imamoto.

At least 73 records · Page 4Linked to original sources
PubMed1986

Genetic characterization of the gene hupB encoding the HU-1 protein of Escherichia coli.

The gene hupB encoding the HU-1(HU beta) protein of Escherichia coli was mapped between proC at min 9 and minA at min 10 on the K-12 genome by plasmid integration and chromosome transfer studies. Genetic studies using plasmid rescue techniques demonstrated that the lon gene is located very close to the 5' end of hupB and that the two genes are both transcribed clockwise on the E. coli map [Bachmann, Microbiol. Rev. 47 (1983) 180-230].

Bacterial Proteins↗
PubMed1985

Purification of the NusB gene product of Escherichia coli K12.

The nucleotide sequence of the entire nusB gene of Escherichia coli has recently been determined and the amino acid sequence of its product deduced (Ishii et al. 1984; Swindle et al. 1984). The NusB protein was purified by chromatography on Sephadex G-100, phosphocellulose and hydroxylapatite. Purification of the protein was monitored using 14C-labelled NusB protein, which was synthesized in a maxicell containing an nusB plasmid as a marker. The final product, which was at least 95% pure as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, had a molecular weight of about 16,000 and an isoelectric point of about 7.3. Analytical data on the amino acid composition of the purified protein agreed with that deduced from the DNA sequence and indicated that this protein was indeed the product of the nusB gene.

Amino Acid Sequence↗
PubMed1985

Molecular cloning and nucleotide sequence of the HU-1 gene of Escherichia coli.

The Escherichia coli HU-1 was cloned by use of mixed synthetic oligonucleotides (17-mer) predicted from a portion of its amino acid sequence. The amino acid sequence of the HU-1 protein deduced from the nucleotide sequence is in good agreement with the published sequence. The nucleotide sequence has a possible promoter and a typical ribosomal binding site upstream from the translational initiation codon (GUG) of the HU-1 gene.

Amino Acid Sequence↗
PubMed1984

Molecular cloning and nucleotide sequencing of the nusB gene of E. coli.

The nusB gene of E. coli has been cloned in plasmid pBR322. Using genetic complementation as an assay for the gene, its location in subclones was analyzed, and the nucleotide sequence of this gene and its flanking regions was determined. The coding region consists of 417 base pairs (bp), which specify a protein of 139 amino acids, and the calculated molecular weight of the nusB protein is 15,702. The nusB protein contains 20 acidic and 21 basic amino acids. A significant promoter sequence was not found to be located in the region upstream from the translational initiation codon. The possibility that the nusB gene consists of an operon is discussed. After the coding region, there is a G-C rich inverted repeat sequence followed by a run of Ts, which could be a transcriptional terminator of the nusB gene.

Amino Acid Sequence↗
PubMed1984

The nucleotide sequence of the cloned nusA gene and its flanking region of Escherichia coli.

The nucleotide sequence of the promoter-proximal portion of the nusA operon including the genes for tRNAMetf2, a 15 kilodalton protein and the initial portion of the nusA gene has been determined previously (1). Here, we report the sequence for the entire nusA gene and its flanking region. The open reading frame, consisting of 1,482 nucleotides, was identified as that of the nusA protein on the basis of agreement of the amino acid sequence deduced from the DNA sequence with the N-terminal sequence of the purified nusA protein. The molecular weight of 54,417 daltons calculated for the 494 amino acid polypeptide is significantly lower than that determined previously by SDS polyacrylamide gel analysis. The nusA gene is immediately followed by another open reading frame encoding a polypeptide of at least 22 amino acids, which was identified as the initial portion of the infB structural gene. In the spacer region of 24 base pairs between the nusA and infB structural genes there is no significant DNA sequence that fits the canonical transcriptional termination signal or promoter sequence. We suggest, therefore, that the genes for tRNAMetf2, a 15 kilodalton protein, the nusA protein and IF2 alpha, aligned in this order, are co-transcribed.

Bacterial Proteins↗
PubMed1984

Isolation and characterization of nucleoid proteins from Escherichia coli.

Of the molecular species of proteins associated with the nucleoids of Escherichia coli cells, those with relatively high affinity to bind to DNA were isolated and characterized. Seven classes of nucleoid proteins with molecular weights of 9,000, 17,000 (two molecular species), 22,000, 24,000, 27,000 and 28,000 were isolated at more than 90% purity or were partially purified. On the basis of its amino acid composition and other chemical properties, the 9,000 dalton protein was identified as HLP II (or HU protein or BH2) (Pettijohn 1982; Rouvière-Yaniv and Gros 1975; Varshavsky et al. 1978). The 17 K protein consisted of two molecular species and one of these, 17 K (a) protein, seemed to be identical with HLPI (or protein 1 or BH1) reported previously (Pettijohn 1982; Varshavsky et al. 1977; Varshavsky et al. 1978). The 26 K protein was identical to the 22 K protein (Kishi et al. 1982). The 27 K protein showed immunological cross-reactivity with the antibody for histone H2A and was thus identified as the H protein reported previously (Hübscher et al. 1980). Two basic proteins, 9 K and 17 K(a), showed relatively high binding affinities to DNA, while the 28 K protein showed moderate binding affinity. The biological significance of these nucleoid proteins, which constitute a family of proteins participating in formation of the nucleoid structure, is discussed.

Bacterial Proteins↗
PubMed1984

Transcription of the trpR gene of Escherichia coli: an autogeneously regulated system studied by direct measurements of mRNA levels in vivo.

The expression of the trpR gene of Escherichia coli was investigated by measuring trpR messenger RNA levels in vivo under various physiological conditions. Trp repressor, when present, led to significant decreases in the amount of trpR message produced; this effect was enhanced by providing excess L-tryptophan to the system. In the absence of Trp repressor, no changes in trpR message levels were observed under any of the conditions employed. Sedimentation profiles of trpR mRNA revealed a single species under all circumstances. These results suggest that autogenous repression alone acts to regulate transcription of the trpR gene. The activity of the trpR promoter in vivo was evaluated using a trpR-lacZ operon fusion. Very good agreement was found between relative promoter activity and trpR message levels under all experimental conditions.

Bacterial Proteins↗
PubMed1984

tRNAMetf2 gene in the leader region of the nusA operon in Escherichia coli.

The promoter-proximal portion of the operon containing the Escherichia coli nusA gene has been cloned. Its nucleotide sequence shows that genes for tRNAMetf2 and a 15-kilodalton protein of unknown function precede the nusA protein gene. The sequence suggests that the three genes form a single transcription unit. Consistent with this hypothesis, purified RNA polymerase formed full-length transcripts on the cloned DNA in vitro, although transcription was frequently arrested at the intercistronic site(s) between the gene for tRNAMetf2 and the 15-kilodalton protein.

Bacterial Proteins↗
PubMed1982

Involvement of the nusB gene products in transcription of Escherichia coli tryptophan operon in vitro.

Synthesis of trp mRNA in vitro directed by plasmid DNA carrying the entire trp operon was studied using crude protein extracts (S-100) from Escherichia coli strains carrying the nusA or nusB mutation or both. It was found that the levels of trp mRNA transcribed from the promoter-distal genes (trpCBA) relative to that from the promoter-proximal genes (trpED) was markedly lower with extracts from the nus- mutants than that from the nus+ strain. Kinetic experiments suggest that termination of RNA transcripts at intragenic transcriptional barriers is prevented by the nus gene products from allowing efficient expression of the operon.

Bacterial Proteins↗
PubMed1982

Comparative studies of the effect of DNA superhelicity on in vitro transcription catalyzed by Escherichia coli S100 proteins and purified RNA polymerase.

The effect of DNA superhelicity on in vitro transcription catalyzed by purified Escherichia coli RNA polymerase or S100 crude extract proteins was examined at various KCl concentrations. DNA from a recombinant plasmid pMT48 harboring the pL promotor-controlled fused N-trp genes and the pR promotor-controlled tof (cro) gene was employed as a template. Stimulation of transcription by superhelicity is generally more pronounced with the S100 crude extract proteins than with pure RNA polymerase. At KCl concentrations lower than 100 mM with pure RNA polymerase, there is no significant difference in the template activity between the supercoiled and relaxed forms of pMT48 DNA. In contrast, the dependence of efficient template activity on superhelicity is great over a whole range of KCl concentrations from 1.7 to 400 mM in the system using the S100 crude extract. The relative insensitivity of the pR promotor to superhelicity can be observed in either transcription assay system. Analysis of the kinetics of pL-promoted synthesis of trp mRNA indicates that diminished transcription in vitro on a relaxed template results mainly from less frequent RNA chain initiations, but at least in part from premature arrest of the chain elongation.

Bacterial Proteins↗
PubMed1982

In vivo evidence for nusA and nusB gene function in general transcription of the Escherichia coli genome.

The requirements for nusA and nusB gene products for the effective transcription of E. coli genes, including the trp operon, were demonstrated by analysis of RNA transcripts produced in nusA, nusB and nusAnusB mutants. In the nusA1 mutant, the levels of overall synthesis of both bulk RNA and trp mRNA were reduced more at 37 C than at 30 C, consistent with the idea of temperature-sensitive nus protein function (Friedman et al., 1973). In the nusB27 and nusA1nusB27 mutants (Friedman et al., 1976), decrease in the overall rates of these RNA synthesis was notable even at 30 C. In nus mutants harboring trp delta LD1412, in which the trp operon attenuator site is deleted, the reduction in the trp mRNA level was less severe. Thus, the effect of nus mutations seems to result in part from more frequent transcription termination at the attenuator site. Also in nusA1nusB27 mutants, in which the distal portion of the trp operon is deleted, the trp mRNA level was not reduced much. Thus, transcription in the nus- mutants seems to be frequently and prematurely arrested at sites along the trp operon.

Escherichia coli↗