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T Yura

Publications and source records attributed to T Yura.

At least 19 recordsLinked to original sources
PubMed1992

Systematic sequencing of the Escherichia coli genome: analysis of the 0-2.4 min region.

A contiguous 111,402-nucleotide sequence corresponding to the 0 to 2.4 min region of the E. coli chromosome was determined as a first step to complete structural analysis of the genome. The resulting sequence was used to predict open reading frames and to search for sequence similarity against the PIR protein database. A number of novel genes were found whose predicted protein sequences showed significant homology with known proteins from various organisms, including several clusters of genes similar to those involved in fatty acid metabolism in bacteria (e.g., betT, baiF) and higher organisms, iron transport (sfuA, B, C) in Serratia marcescens, and symbiotic nitrogen fixation or electron transport (fixA, B, C, X) in Azorhizobium caulinodans. In addition, several genes and IS elements that had been mapped but not sequenced (e.g., leuA, B, C, D) were identified. We estimate that about 90 genes are represented in this region of the chromosome with little spacer.

Bacterial Proteins↗
PubMed1992

Binding of RepE initiator protein to mini-F DNA origin (ori2). Enhancing effects of repE mutations and DnaJ heat shock protein.

Replication of mini-F plasmid in Escherichia coli requires the plasmid-encoded RepE initiator protein and a number of host factors and is regulated by interaction of RepE with specific sequences near the replication origin, ori2. We have examined DNA binding properties of several hyperactive mutant RepE proteins with single amino acid substitutions. Plasmids carrying these (repE) mutations, unlike the parental plasmid, can replicate in bacterial hosts lacking the heat shock sigma factor (sigma 32) or deficient in the DnaK, DnaJ, or GrpE heat shock protein. Using gel-retardation assays, the mutant RepE proteins were shown to bind the ori2 repeated sequences with much increased affinities compared to the wild type RepE, whereas they bound to the repE operator with slightly reduced affinities. These results agreed well with the properties of mutant RepE proteins studied in vivo and accounted for the high RepE initiator activities and the high copy numbers of mutant plasmids. In addition, the DnaJ heat shock protein was found to markedly enhance the binding of wild type RepE to ori2 or the operator. DnaK protein with or without ATP failed to show such enhancements. Thus, among the heat shock proteins required for mini-F replication, DnaJ appears to play a major role in RepE binding to ori2 and the operator, perhaps accompanied by RepE activation.

Autoradiography↗
PubMed1992

DnaK and DnaJ heat shock proteins participate in protein export in Escherichia coli.

In Escherichia coli secreted proteins must be maintained in an export-competent state before translocation across the cytoplasmic membrane. This function is carried out by a group of proteins called chaperones. SecB is the major chaperone that interacts with precursor proteins before their secretion. We report results indicating that the DnaK and DnaJ heat shock proteins are also involved in the export of several proteins, most likely by acting as their chaperones. Translocation of alkaline phosphatase, a SecB-independent protein, was inhibited in dnaK- and dnaJ- mutant strains, suggesting that export of this protein probably involves DnaK and DnaJ. In addition, DnaK and DnaJ play a critical role in strains lacking SecB. They are required both for viability and for the residual processing of the SecB-dependent proteins LamB and maltose-binding protein (MBP) seen in secB null strains. Furthermore, overproduction of DnaK and DnaJ permits strains lacking SecB to grow in rich medium and accelerates the processing of LamB and MBP. These results suggest that under conditions where SecB becomes limiting, DnaK and DnaJ probably substitute for SecB and facilitate protein export. This provides the cell with a mechanism to overcome a temporary imbalance in the secretion process caused by an abrupt expansion in the pool of precursor proteins.

Alkaline Phosphatase↗
PubMed1992

Mini-F plasmid mutants able to replicate in Escherichia coli deficient in the DnaJ heat shock protein.

A subset of Escherichia coli heat shock proteins, DnaJ, DnaK, and GrpE, is required for mini-F plasmid replication, presumably at the step of functioning of the RepE initiator protein. We have isolated and characterized mini-F plasmid mutants that acquired the ability to replicate in the Escherichia coli dnaJ259. The mutant plasmids were found to replicate in any of dnaJ, dnaK, and grpE mutant hosts tested. In each case, the majority of the mutant plasmids carried a unique amino acid alteration in a localized region of repE coding sequence and showed an increased copy number, whereas the minority contained a common single base change (C to T) in the promoter/operator region and produced an increased amount of RepE. All RepE proteins with altered residues (between 92 and 134) exhibited increased initiator activities (hyperactive), and many showed reduced repressor activities as well, indicating that this region is important for the both major functions of RepE protein. These results together with evidence reported elsewhere indicate that the subset of heat shock proteins serves to activate RepE protein prior to or during its binding to the replication origin and that the mutant RepE proteins are active even in their absence. We also found that a C-terminal lesion (repE602) reduces the initiator activity particularly of some hyperactive mutant RepE proteins but does not affect the repressor activity. This finding suggests a functional interaction between the central and C-terminal regions of RepE in carrying out the initiator function.

Bacterial Proteins↗
PubMed1992

Sensitization of Escherichia coli cells to oxidative stress by deletion of the rpoH gene, which encodes the heat shock sigma factor.

A deletion in the rpoH gene greatly increased the sensitivity of Escherichia coli sodA sodB mutants to oxidative stress. The effect of the rpoH deletion on sodA+ sodB+ cells was only marginal. Mutations in heat shock genes singly sensitized sodA sodB double mutant cells to plumbagin. sodA sodB double mutants were neither more sensitive nor more resistant to thermal stress than the wild type.

Chromosome Deletion↗
PubMed1992

Successful resection of pheochromocytoma in a hemodialysis patient.

A 45-year-old woman with a pheochromocytoma who had been on regular hemodialysis for 4 years and underwent successful surgery is described. Careful preoperative management, including the use of prazosin and weight control, was carried out to prevent severe intraoperative and postoperative cardiovascular complications. Prazosin was given at an initial dose of 0.5 mg/day, and the dosage was increased to 20 mg/day prior to surgery. The increase in intravascular volume led to a gain of 3 kg in body weight. No deterioration of the cardiovascular or respiratory function was caused by these maneuvers, and surgery was performed without significant complications except for a rapid rise of blood pressure during tumor resection. To our knowledge, only one similar case report could be found in the English literature.

Adrenal Gland Neoplasms↗
PubMed1992

Dopaminergic modulation of the pressure-natriuresis response in rats.

OBJECTIVE: The present study was carried out to examine the involvement of dopamine in the pressure-natriuresis phenomenon which has been postulated as a major regulator of extracellular fluid volume and thereby arterial pressure. DESIGN: Dopaminergic modulation of the pressure-natriuresis response was studied in the innervated and denervated rat kidney, to allow a distinction between the effects of neural and extraneural dopamine. METHODS: The pressure-natriuresis response was studied in anesthetized Sprague-Dawley rats, in which neural and hormonal influences on the kidney were fixed by denervating the kidney and by intravenous infusion of aldosterone, hydrocortisone, vasopressin and norepinephrine. The innervation to the kidney remained intact in some experiments with the selective dopamine-1 antagonist SCH 23390. Urinary excretion of dopamine during the pressure-natriuresis response was also examined in the innervated and denervated rat kidney. RESULTS: Although infusion of dopamine at a dose of 2 micrograms/kg per min had no effect on the pressure-natriuresis response in rats in which neural and hormonal influences on the kidney were fixed, the slopes of the relations between urine flow, sodium excretion and mean arterial pressure in rats given 10 micrograms/kg per min dopamine were significantly greater than those found in the control rats. Renal plasma flow increased significantly in the dopamine-treated rats whilst glomerular filtration rate did not differ between the control and dopamine-treated rats. The dopamine-induced increase in the slope of pressure-natriuresis relationship and renal plasma flow were completely blocked by 0.5 micrograms/kg per min SCH 23390. However, infusion of SCH 23390 alone at 0.5 micrograms/kg per min did not significantly alter the pressure-natriuresis response in rats with either denervated or innervated kidney. In addition, urinary excretion of dopamine derived from neither neural nor extraneural origins was altered in parallel with variations in mean arterial pressure. CONCLUSION: These results suggest that exogenous administration of dopamine may affect the pressure-natriuresis response by altering the magnitude of arterial pressure-induced changes in tubular sodium reabsorption, via an action of dopamine-1 receptors. However, endogenous dopamine does not appear to be capable of modulating the pressure-natriuresis response.

Animals↗
PubMed1992

[Doppler ultrasound measurement of phasic renal arterial blood flow velocity in patients with chronic glomerulonephritis].

The phasic renal arterial blood flow velocity was measured using a Doppler-Based Toshiba SSH-160A scanner in 25 healthy subjects and 78 patients with chronic glomerulonephritis. Renal arterial blood flow at the renal hilum was visualized with color Doppler ultrasound, and the velocity waveform was obtained by pulsed Doppler ultrasound. The velocity waveform was then analyzed to give the peak systolic velocity (S), end-diastolic velocity (D), resistive index (RI), and pulsatility index (PI). Creatinine clearance correlated with S (r = 0.76), D (r = 0.80), RI (r = -0.74), and PI (r = -0.85). The split renal glomerular filtration rate, calculated by a method which makes use of the early renal uptake of Tc-99m DTPA, also correlated well with these parameters. These findings suggest that renal arterial blood flow as detected by Doppler ultrasound may be useful for the noninvasive, direct, rapid, and simple evaluation of renal hemodynamics and renal function, although various modifying factors also need to be considered.

Adolescent↗
PubMed1991

Interplay of two cis-acting mRNA regions in translational control of sigma 32 synthesis during the heat shock response of Escherichia coli.

When Escherichia coli cells are transferred from 30 degrees C to 42 degrees C, transcription from specific promoters recognized by RNA polymerase containing sigma 32 (the rpoH gene product) is transiently activated, resulting in induction of heat shock proteins. Transcription from heat shock promoters is activated by an increased cellular concentration of sigma 32 due to enhanced synthesis and stabilization. We have constructed and examined the expression of mutant derivatives (deletions and base substitutions) of rpoH-lacZ gene fusion. Synthesis of a sigma 32-beta-galactosidase fusion protein was found to be regulated at the translational level involving two distinct 5'-proximal rpoH coding regions. A small region immediately downstream of the initiation codon is required for potentially high-level expression, whereas a much larger internal region is required for thermal regulation--namely, repression at low temperature or nonstress conditions. The two mRNA regions act as positive and negative cis elements, respectively, in controlling rpoH translation. We propose that an interplay between these RNA regions involving secondary structure formation is important in regulating translation initiation and that transient disruption of secondary structure represents a primary step of the heat shock response.

Base Sequence↗
PubMed1991

Regulation of the heat shock response in E coli: involvement of positive and negative cis-acting elements in translation control of sigma 32 synthesis.

When cells of E coli are transferred from 30 to 42 degrees C, the cellular level of sigma 32 (rpoH gene product) increases transiently, resulting in increased transcription of a set of heat shock genes. Both increased synthesis and increased stability of sigma 32 contribute to transient accumulation of sigma 32. Evidence suggests that synthesis of sigma 32 is enhanced primarily at the level of rpoH translation. We have constructed and examined the expression of deletion derivatives of rpoH-lacZ gene fusion at 30 degrees C and after shift to 42 degrees C. It was revealed that two cis-acting sequences within the rpoH coding region are involved in thermal regulation of fusion protein synthesis. One region immediately downstream of the initiation codon is required for high level expression, whereas the other internal region is involved in repression at low temperature. Thus, these regions act as positive and negative cis-elements in thermal regulation of rpoH translation. The rpoH mRNA secondary structure model suggesting an interplay between the two regions has been proposed to account for the temperature-induced sigma 32 synthesis as a primary cellular response to the heat shock stress.

Base Sequence↗
PubMed1991

Expression of ClpB, an analog of the ATP-dependent protease regulatory subunit in Escherichia coli, is controlled by a heat shock sigma factor (sigma 32).

Escherichia coli K-12 produces at least two ATP-dependent proteases, Lon (La) and Clp (Ti), the latter consisting of a regulatory subunit (ClpA) and a proteolytic subunit (ClpP). The gene clpB encoding an analog of ClpA had been found at 57 min on the E. coli chromosome. Cloning and examination of novel heat shock promoters led us to identify a major clpB promoter specifically controlled by a heat shock sigma factor, sigma 32 (the rpoH [= htpR] gene product). beta-Galactosidase synthesis from a PclpB-lacZ operon fusion was transiently induced upon temperature shift from 30 to 42 degrees C, and the induction depended on the rpoH function. Chromosomal clpB transcripts also increased upon temperature upshift and were totally absent in the rpoH deletion strain. In the in vitro transcription experiments, the clpB promoter was specifically recognized and transcribed by RNA polymerase-sigma 32. Nucleotide sequencing and determination of mRNA start sites permitted us to identify a major heat shock promoter located upstream of the clpB coding sequence. The results clearly indicate that clpB expression is under direct control of sigma 32. Since ClpP was recently shown to be a sigma 32-dependent heat shock protein, the present finding suggests the possibility that a potential ATP-dependent protease, ClpB-ClpP complex, plays an important role against thermal stress in E. coli.

ATP-Dependent Proteases↗
PubMed1991

Mini-F plasmid mutants able to replicate in the absence of sigma 32: mutations in the repE coding region producing hyperactive initiator protein.

Mini-F plasmids cannot replicate in Escherichia coli strains (delta rpoH) lacking sigma 32, presumably because transcription of the repE gene encoding the replication initiator protein (RepE protein) depends mostly on RNA polymerase containing sigma 32. We have isolated and characterized mini-F mutants able to replicate in delta rpoH cells. Contrary to the initial expectation, five mutants with mutations in the repE coding region that produce altered RepE proteins were obtained. The mutations caused replacement of a single amino acid: the 92nd glutamic acid was replaced by lysine (repE10, repE16, and repE25) or glycine (repE22) or the 109th glutamic acid was replaced by lysine (repE26). These plasmids overproduced RepE protein and exhibited very high copy numbers. Two major activities of mutated RepE proteins have been determined in vivo; the autogenous repressor activity was significantly reduced, whereas the initiator activity was much enhanced in all mutants. These results indicate the importance of a small central region of RepE protein for both initiator and repressor activities. Thus the decreased repE transcription in delta rpoH cells can be compensated for by an increased initiator activity and a decreased repressor activity of RepE, resulting in the increased synthesis of hyperactive RepE protein.

Amino Acid Sequence↗
PubMed1991

Noninvasive detection and monitoring of renal arteriovenous fistula by color Doppler.

The diagnosis of a renal arteriovenous fistula is usually confirmed by angiography. Described is the utilization of color Doppler ultrasound to monitor a renal arteriovenous fistula before and after treatment by transcatheter steel coil embolization in a 63-year-old woman. Using color Doppler, the arteriovenous fistula with an aneurysmal lesion was clearly visualized. A pulsed-wave Doppler analysis showed increased flow velocity and decreased pulsatility in the supplying artery. After successful transcatheter occlusion of the fistula, these findings disappeared. The Doppler ultrasound technique is likely to be useful to detect and monitor a renal arteriovenous fistula noninvasively, simply, and quickly.

Arteriovenous Fistula↗
PubMed1991

Total and split renal function assessed by ultrasound Doppler techniques.

We evaluated total and split renal functions from the pattern for renal arterial blood flow detected by ultrasound Doppler in healthy subjects and patients with varying degrees of renal function and disorders other than renovascular hypertension or severe aortic valvular disease. A renal-time pulsed ultrasonic echo-Doppler device at 2.5 MHz was used with a translumbar approach. The ratio of peak diastolic (D) to systolic (S) velocity correlated well with both p-aminohippurate clearance and creatinine clearance. Acceleration time was correlated with the clearance of neither compound. To evaluate the clinical usefulness of ultrasound Doppler in the assessment of split renal function, we compared the D/S ratio with the renal function obtained by radionuclide methods for individuals. The split renal glomerular filtration rate, calculated by a method which makes use of the early renal uptake of 99mTc-diethylenetriam-inepentaacetic acid, correlated well with the D/S ratio. These results indicate that the ultrasonic measurement of renal arterial blood flow by the pulsed Doppler method should be useful for assessment of total and split renal functions.

Adolescent↗
PubMed1979

Specialized transducing phage lambda carrying the genes for coupling factor of oxidative phosphorylation of Escherichia coli: increased synthesis of coupling factor on induction of prophage lambda asn.

Studies were made of the synthesis of the coupling factor complex (F1--F0) of oxidative phosphorylation after prophage induction of a set of Escherichia coli strains lysogenic for defective transducing phage lambda asn, lambda uncA, or lambda bglC. The transducing phages had been isolated from a strain of E. coli carrying prophage lambda cI857 S7 within the bglB gene located near the unc gene cluster [Miki, T., Hiraga, S., Nagata, T. & Yura, T. (1978) Proc. Natl. Acad. Sci. USA 75, 5099--5103]. When lysogenic cells carrying lambda asn and lambda cI857 S7 were induced at high temperature, synthesis of the F1-ATPase portion of the complex increased to severalfold that of the noninduced cells. In contrast, no increase was observed upon thermoinduction of cells carrying lambda uncA or lambda bglC. The number of membrane sites that could bind purified F1-ATPase also increased significantly upon induction by lambda asn but not by lambda uncA or lambda bglC. In addition, F1-depleted membranes prepared from lambda asn-induced bacteria required more dicyclohexylcarbodiimide to seal the proton pathway than did those from noninduced bacteria. These results strongly suggest that lambda asn carries a set of bacterial genes coding for all the F1 polypeptides (the alpha, beta, gamma, delta, and probably the epsilon subunits) and at least some of the genes involved in formation of F0 polypeptides. Although lambda uncA carries the structural gene (uncA) for the alpha subunit of F1-ATPase, it apparently does not carry the whole set of F1--F0 genes.

Adenosine Triphosphatases↗
PubMed1979

Genetic studies of an Escherichia coli K-12 temperature-sensitive mutant defective in membrane protein synthesis.

The mutant divE42(Ts) of Escherichia coli K-12, defective in the synthesis of membrane proteins and in the transcription of the lac operon at high temperature, has been further characterized. It was found that a mutation (divE42) located at about min 22 on the E. coli chromosome map is responsible for the Lac- phenotype and temperature-sensitive growth. The mutation could be contransduced with serC, pyrD, or pyrC by phage P1 at a frequency of 4, 16, or 0.5%, respectively, the gene order being serC-pyrD-ompA-sulA-divE-pyrC. Examination of temperature-independent revertants and Pyr+ transductants revealed that all the mutant phenotypes examined (deficiencies in the increase of activities of some membrane enzymes, expression of the lac operon, and synthesis of several other proteins) are due to a single mutation (divE42) which is recessive to the wild-type (divE+) allele. Protein synthesis in the mutant was also analyzed by dodecyl sulfate-polyacrylamide gel electrophoresis. Synthesis of a number of proteins, including membrane proteins, was found to decrease significantly, whereas that of an elongation factor, EF-Tu, increased upon transfer of a log-phase culture to high temperature (42 degrees C). These effects of temperature shift-up on protein synthesis were evident within 5 min under the conditions used.

Bacterial Proteins↗