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M Sauter

Publications and source records attributed to M Sauter.

7 recordsLinked to original sources
PubMed1992

Mutational analysis of the operon (hyc) determining hydrogenase 3 formation in Escherichia coli.

In-frame deletions were introduced into each of the eight genes of the hyc operon coding for products required for the formation of the formate hydrogenlyase (FHL) system. The deletions were transferred to the chromosome and the resulting mutants were analysed for development of formate dehydrogenase H and hydrogenase 1, 2 and 3 activity. It was found that hycA, the promoter-proximal gene, is a regulatory gene and that it codes for a product counteracting transcriptional activation by FhlA. Deletions within the hycB to hycH genes specifically affected formate dehydrogenase H activity or hydrogenase 3 activity, or both. None of the mutations affected hydrogenase 1 or 2 activity. A model is proposed for the functional interaction of the different hyc operon gene products in the formate hydrogenlyase complex, which is based on the results of the mutational analysis, on the determination of the subcellular localization of the FdhF, HycE, HycF and HycG polypeptides and on the similarity of hyc gene product sequences with those from other hydrogenase systems. HycH, the product of the most promoter-distal gene, does not seem to form part of the functional FHL complex but rather is required for the conversion of a precursor form of the large subunit of hydrogenase 3 into the mature form.

Amino Acid Sequence↗
PubMed1991

Immunological characterization of the Epstein-Barr virus phosphoprotein PP58 and deoxyribonuclease expressed in the baculovirus expression system.

The open reading frames of the phosphoprotein pp58 (BMRFI) and the deoxyribonuclease (BGLF5) of the Epstein-Barr-virus (EBV) strain M-ABA were cloned in the baculovirus expression vectors pAc373 and pAc360 and expressed in the Spodoptera frugiperda (SF158) insect cells. The recombinant phosphoprotein pp58 expressed in SF158 cells was recognized by the anti-pp58 rabbit anti-sera which were generated by immunizing rabbits with a TrpE-BMRFI fusion protein expressed in E. coli. DNA-cellulose chromatography showed that the recombinant pp58 exhibited DNA-binding activities. Immunofluorescence, immunoblot and ELISA analysis indicated that sera from patients with nasopharyngeal carcinoma (NPC) contained antibodies against pp58. The recombinant EBV DNase expressed in SF158 cells was recognized by the anti-EBV DNase rabbit anti-sera which were generated by immunizing rabbits with a TrpE-C-terminal part of BGLF5 fusion protein expressed in E. coli. The anti-EBV DNase rabbit anti-sera recognized also a protein of about 52 kDa in the EBV-harboring human B-cell lines Raji, Jijoye, B95-8, M-ABA and BL74 induced by TPA and n-butyrate. The recombinant EBV DNase exhibited exonuclease and endonuclease activities, a requirement for magnesium, and a high pH optimum (8.0). Its enzyme activities could be inhibited by sera from NPC patients and anti-EBV DNase rabbit anti-sera. Comparable studies of Raji EBV-DNase and recombinant EBV-DNase implied that recombinant EBV-DNase could also be used in the enzyme activity assay for the detection of NPC. In contrast to the enzyme inhibition test, immunofluorescence and immunoblot analysis demonstrated that the recombinant EBV DNase exhibited only a weak immunological reaction with NPC sera.

Animals↗
PubMed1990

Flow cytometric analysis of Epstein-Barr virus (EBV) latent membrane protein expression in EBV-infected Raji cells.

In cultures of the latently Epstein-Barr virus (EBV)-infected Burkitt's lymphoma cell line Raji, the detectable amount of the EBV-encoded latent membrane protein (LMP) is transiently increased after addition of fresh nutrient medium containing foetal calf serum. In the current study, the relative amount of LMP and DNA in Raji cells was determined by biparametric flow cytometry analysis at different times after the addition of fresh medium with 10% foetal calf serum to a dense Raji culture. A transient increase in the proportion of LMP-positive cells was observed during the lag phase of the culture. Subsequently, a subpopulation of cells, which had been arrested in the G0 or G1 phase, simultaneously started to progress through the cell cycle. Neither the amount of LMP in the cells, nor the enhanced expression of LMP, was restricted to a certain phase of the cell cycle. Further analysis revealed that the number of LMP-positive cells proceeding simultaneously from the G1 to the S phase of the cell cycle is about the same as the total number of cells changing phases. These results suggest that LMP expression might be one step in the pathway leading to growth activation of resting cells in cultures of the immortalized Raji cell line.

Antigens, Viral↗
PubMed1990

Nucleotide sequence and expression of an operon in Escherichia coli coding for formate hydrogenlyase components.

An 8kb segment of DNA from the 58/59 min region of the E. coli chromosome, which complements the defect of a mutant devoid of hydrogenase 3 activity, has been sequenced. Eight open reading frames were identified which are arranged in a transcriptional unit; all open reading frames were transcribed and translated in vivo in a T7 promoter/polymerase system. Analysis of the amino acid sequences derived from the nucleic acid sequences revealed that one of them, open reading frame 5 (ORF5), exhibits significant sequence similarity to conserved regions of the large subunit from Ni/Fe hydrogenases. Two of the open reading frames (orf2, orf6) code for proteins apparently carrying iron-sulphur clusters of the 4Fe/4S ferredoxin type. The product of one of the open reading frames, orf7, displays extensive sequence similarity with protein G from the chloroplast electron transport chain. ORF3 and ORF4, on the other hand, are extremely hydrophobic proteins with nine and six putative transmembrane helices, respectively. Over a limited hydrophilic sequence stretch, bordered by putative transmembrane areas, ORF3 and ORF4 exhibit homology with subunits 4 and 1 of mitochondrial and plastid NADH-ubiquinol oxidoreductases, respectively. The operon described, therefore, appears to comprise genes for redox carriers linking formate oxidation to proton reduction and for a hydrogenase of hitherto unique composition.

Aldehyde Oxidoreductases↗
PubMed1990

Transcriptional analysis of the gene encoding pyruvate formate-lyase-activating enzyme of Escherichia coli.

The act gene of Escherichia coli encodes the pyruvate formate-lyase-activating enzyme which is necessary for the post-translational modification of pyruvate formate-lyase. The gene is located 191 bp downstream from the pfl structural gene. Northern blot analysis revealed that the act transcript is monocistronic and that transcription is independent of pfl gene expression. Through mapping of the 5' and 3' ends of the act transcript, sequences could be identified showing similarity to both an Escherichia coli sigma 70 promoter and to a rho-independent transcription terminator. Expression of the act gene was analysed with the aid of chromosomally integrated transcriptional and translational lacZ fusions. The results verified that the act gene is transcribed from its own promoter and that expression of the gene is essentially constitutive. Anaerobiosis led only to a two-fold increase in expression over that observed in aerobically grown cells and this elevated expression was independent of the transcriptional regulator, Fnr. Moreover, effectors such as pyruvate and nitrate, which substantially influence anaerobic transcription of the pfl gene, did not affect act gene expression.

Acetyltransferases↗
PubMed1976

Xerophthalmia and measles in Kenya.

In many African countries measles is considered to be an important cause of blindness. On the basis of his observations in Kenya and Tanzania in 1972 Franken presumed, however, that in the majority of these cases xerophthalmia was the real cause of blindness, precipitated by the "catalyst" measles. In order to gain a better understanding of this important complicated problem, we performed in the first half of 1974 an investigation in Kenya into the prevalence of xerophthalmia. In December 1974 we had the opportunity to evaluate our Kenyan findings on Java, in the company of Dr. J. ten Doesschate and Professor H.A.P.C. Oomen. The results of this investigation in Kenya and Indonesia are presented in this thesis. (see article) 1. Xerophthalmia occurred nearly everywhere in Kenya in 1974. This demonstrates the prevalence of xerophthalmia in communities which - do not have rice but - have maize for their staplefood. 2. Xerophthalmia appears to be the main cause of blindness in Kenyan children. 3. Measles often plays - by means of local and general "catalysing" effects - an important role in the development of blindness caused by xerophthalmia. 4. In well-nourished children measles is of no consequence as a cause of blindness. 5. Vital staining by 1% rose bengal or 1% lissamine green appears to be a real asset for the early diagnosis of xerophthalmia in Health Centres and in field surveys. This method is therefore of great importance for the prevention of severe, blindness inducing vitamin A deficiency.

Adolescent↗