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R Kreutzer

Publications and source records attributed to R Kreutzer.

45 records · Page 3Linked to original sources
PubMed1990

Activation of the Klebsiella pneumoniae nifU promoter: identification of multiple and overlapping upstream NifA binding sites.

The Klebsiella pneumoniae nifU promoter is positively controlled by the NifA protein and requires a form of RNA polymerase holoenzyme containing the rpoN encoded sigma factor, sigma 54. Occupancy of the K. pneumoniae nifU promoter by NifA was examined using in vivo dimethyl sulphate footprinting. Three binding sites for NifA (Upstream Activator Sequences, UASs 1, 2 and 3) located at -125, -116 and -72 were identified which conform to the UAS consensus sequence TGT-N10-ACA. An additional NifA binding site was identified at position -90. The UASs located at -125 (UAS1) and -116 (UAS2) overlap and do not appear to bind NifA as independent sites. They may represent a NifA binding site interacting with two NifA dimers. UAS3 is located at -72, and abuts a binding site for integration host factor (IHF) and is not normally highly occupied by NifA. In the absence of IHF UAS3 showed increased occupancy by NifA. Mutational and footprinting analysis of the three UASs indicates (1) IHF and NifA can compete for binding and that this competition influences the level of expression from the nifU promoter (2) that UAS2 is a principle sequence of the UAS 1,2 region required for activation and (3) that none of the NifA binding sites interacts with NifA independently. In vivo KMnO4 footprinting demonstrated that NifA catalyses open complex formation at the nifU promoter. IHF was required for maximal expression from the nifU and nifH promoters in Escherichia coli, and for the establishment of a Nif+ phenotype in E. coli from the nif plasmid pRD1.

Bacterial Proteins↗
PubMed1990

The influence of the Klebsiella pneumoniae regulatory gene nifL upon the transcriptional activator protein NifA.

The influence of the Klebsiella pneumoniae nifL gene product upon the interaction of the transcriptional activator protein NifA with the nifH promoter has been examined using in vivo dimethylsulphate 'footprinting'. Binding of NifA to the upstream activator sequence (UAS) of the nifH promoter in the presence of the NifL protein was observed under nitrogen-limiting growth conditions. Growth in the presence of NH4+ or addition of NH4+ to nitrogen-limited cells diminished the interaction of NifA with the UAS when NifL was present. Repression of nif transcription by NifL may therefore involve an interaction between NifL and NifA which reduces the affinity of NifA for the UAS.

Ammonia↗
PubMed1989

Identification and characterization of the nifH and nifJ promoter regions located on the nif-plasmid pEA3 of Enterobacter agglomerans 333.

Small restriction fragments of the plasmid-borne Enterobacter agglomerans 333 nif region were cloned into a promoter probe plasmid as transcriptional fusions with the lacZ gene. Identification of NifA-dependent promoters was accomplished by using a compatible plasmid which constitutively expresses the Klebsiella pneumoniae nifA gene. beta-Galactosidase assays showed strong activation of the cloned E. agglomerans promoters in Escherichia coli by the heterologous K. pneumoniae nifA gene product. The positions of the promoter fragments on the corresponding restriction map were determined by Southern hybridization. As confirmed by sequencing data, the nifH and nifJ promoters are situated at opposite end-points of the nif gene group and their -24 to -12 nucleotide sequences are similar to the consensus sequence of NtrA-dependent promoters. Also, typical NifA-binding motifs are present in both promoters. The agreement of the promoter proximal regions of nifH and nifJ with the corresponding K pneumoniae sequences is about 80%. Also the upstream regions of these genes are in agreement to some extent.

Base Sequence↗
PubMed1988

Localization and physical mapping of a plasmid-borne 23-kb nif gene cluster from Enterobacter agglomerans showing homology to the entire nif gene cluster of Klebsiella pneumoniae M5a1.

A physical and genetical map of the plasmid pEA3 indigenous to Enterobacter agglomerans is presented. pEA3 is a 111-kb large plasmid containing a 23-kb large cluster of nif genes which shows extensive homology (Southern hybridization and heteroduplex analysis) to the entire nif gene cluster of Klebsiella pneumoniae (Kp) M5a1. All the nif genes on pEA3 are organized in the same manner as in K. pneumoniae, except nifJ, which is located on the left end of pEA3 nif gene cluster (near nifQB). A BamHI restriction map of pEA3 and a detailed restriction map of the 23-kb nif region on pEA3 is also presented. The nif genes of pEA3 showed a low level of acetylene reduction in Escherichia coli, demonstrating that these genes are functional and contain the whole genetic information required to fix nitrogen. The origin of vegetative replication (OriV) of pEA3 was localized about 5.5 kb from the right end of the nif gene cluster. In addition to pEA3, large plasmids from four other strains of E. agglomerans showed homology to all the Kp nif genes tested, indicating that in diazotrophic strains of E. agglomerans nif genes are usually located on plasmids. In contrast, in most of the free-living, nitrogen-fixing bacteria the nif genes are on chromosome.

DNA Restriction Enzymes↗
PubMedDate not supplied

Overproduction of the Thermus thermophilus elongation factor Tu in Escherichia coli.

The elongation factor Tu (EF-Tu) encoded by the tufl gene of the extreme thermophilic bacterium Thermus thermophilus HB8 was expressed under control of the tac promoter from the recombinant plasmid pEFTu-10 in Escherichia coli. Thermophilic EF-Tu-GDP, which amounts to as much as 35% of the cellular protein content, was separated from the E coli EF-Tu-GDP by thermal denaturation at 60 degrees C. The overproduced E coli-born T thermophilus EF-Tu was characterized by: i) recognition through T thermophilus anti-EF-Tu antibodies; ii) analysis of the peptides obtained by cyanogen bromide cleavage; iii) thermostability; iv) guanine nucleotide binding activity in the absence and the presence of elongation factor Ts; and v) ternary complex formation with phenylalanyl-tRNAPhe and GTP.

Base Sequence↗
PubMedDate not supplied

Non-ulcerative cutaneous leishmaniasis in Honduras fails to respond to topical paromomycin.

A double-'blind', placebo-controlled trial of topical therapy with 15% paromomycin (aminosidine) and 10% urea in white paraffin was carried out on 53 patients with non-ulcerating cutaneous leishmaniasis in Honduras. Although the treatment was not effective, several unexpected findings emerged from the trial. Leishmania mexicana was found to be the cause of many of the skin lesions in one of the 2 study sites. These lesions were clinically indistinguishable from those caused by L. chagasi, the aetiologic agent previously found for this form of leishmaniasis. This is the first documented report of L. mexicana in Honduras.

Administration, Topical↗
PubMedDate not supplied

Evaluation of four maternal smoking questions.

OBJECTIVE: The authors evaluated four questions about maternal smoking during pregnancy for use on birth certificates. METHODS: Question 1 (yes/no format) and Question 2 (trimester-specific design) were tested among 1171 women who delivered at two Kaiser Permanente medical centers in northern California. Responses to Questions 1 and 2 were compared with smoking information provided by participants in telephone interviews conducted during pregnancy. Question 3 (multiple choice format) and Question 4 (month- and grouped month-specific design) were tested among 900 women who enrolled in a statewide prenatal screening program and who delivered in 20 hospitals in four Central Valley counties. Responses to Questions 3 and 4 were compared with mid-pregnancy serum cotinine levels. The authors evaluated the four questions in terms of conciseness, response rate, data accuracy, and type of data requested. RESULTS: Questions 1 and 2 were the most concise. Response rates could not be calculated for Questions 1 and 2. Response rates were 86.0% for Question 3 and 74.2% for Question 4. Sensitivity was 47.3% for Question 1, 62.1% for Question 2, 83.8% for Question 3, and 86.7% for Question 4. The types of data requested by Questions 2 and 4 seem to best satisfy the needs of the broad audience of birth certificate users. CONCLUSIONS: No single question was clearly superior. The authors propose a combination of Questions 2 and 4, which asks about average number of cigarettes smoked per day in the three months before pregnancy and in each trimester of pregnancy.

Birth Certificates↗
PubMedDate not supplied

Idiopathic environmental intolerance: case definition issues.

Case definitions of the same phenomenon may be different for different purposes. Case definitions usually become more specific over time as more information about the condition becomes available. Idiopathic environmental intolerance is one of many labels for a heterogeneous group of conditions in which subjects describe multiple symptoms that are attributed to exposure to extremely low doses of common chemicals. Dr. Kreutzer presents issues in case definition for clinical purposes and for population-based studies, and makes recommendations for the clinician and for the public health investigator.

Dose-Response Relationship, Drug↗