| 1. |
- Berglin, Ewa, MD, PhD, 1955-, et al.
(författare)
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Potentiation by L-cysteine of the bactericidal effect of hydrogen peroxide in Escherichia coli
- 1982
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 152:1, s. 81-88
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Tidskriftsartikel (refereegranskat)abstract
- Under anaerobic conditions an exponentially growing culture of Escherichia coli K-12 was exposed to hydrogen peroxide in the presence of various compounds. Hydrogen peroxide (0.1 mM) together with 0.1 mM L-cysteine or L-cystine killed the organisms more rapidly than 10 mM hydrogen peroxide alone. The exposure of E. coli to hydrogen peroxide in the presence of L-cysteine inhibited some of the catalase. This inhibition, however, could not fully explain the 100-fold increase in hydrogen peroxide sensitivity of the organism in the presence of L-cysteine. Of other compounds tested only some thiols potentiated the bactericidal effect of hydrogen peroxide. These thiols were effective, however, only at concentrations significantly higher than 0.1 mM. The effect of L-cysteine and L-cystine could be annihilated by the metal ion chelating agent 2,2'-bipyridyl. DNA breakage in E. coli K-12 was demonstrated under conditions where the organisms were killed by hydrogen peroxide.
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| 2. |
- Carlsson, P., et al.
(författare)
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Genetic Characterization of Bacillus subtilis odhA and odhB, encoding 2-oxoglutarate dehydrogenase and dihydrolipoamide transsuccinylase, respectively
- 1989
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Ingår i: Journal of Bacteriology. - : American Society for Microbiology. - 0021-9193 .- 1098-5530. ; 171:7, s. 3667-3672
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Tidskriftsartikel (refereegranskat)abstract
- The 2-oxoglutarate dehydrogenase complex consists of three different subenzymes, the E1o (2-oxoglutarate dehydrogenase) component, the E2o (dihydrolipoyl transsuccinylase) component, and the E3 (dihydrolipoamide dehydrogenase) component. In Bacillus subtilis, the E1o and E2o subenzymes are encoded by odhA and odhB, respectively. A plasmid with a 6.8-kilobase-pair DNA fragment containing odhA and odhB was isolated. Functional E1o and E2o are expressed from this plasmid in Escherichia coli. Antisera generated against B. subtilis E1o and E2o expressed in E. coli reacted with antigens of the same size from B. subtilis. The nucleotide sequence of odhB and the terminal part of odhA was determined. The deduced primary sequence of B. subtilis E2o shows striking similarity to the corresponding E. coli protein, which made it possible to identify the lipoyl-binding lysine residue as well as catalytic histidine and aspartic acid residues. An mRNA of 4.5 kilobases hybridizing to both odhA and odhB probes was detected, indicating that odhA and odhB form an operon.
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| 3. |
- Faxén, Margareta, et al.
(författare)
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Is efficiency of suppressor tRNAs controlled at the level of ribosomal proofreading in vivo?
- 1988
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 170:8, s. 3756-3760
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Tidskriftsartikel (refereegranskat)abstract
- Ribosomal rpsD mutations did not stimulate nonsense suppressor tRNAs in a general manner according to their increased ribosomal ambiguity and decreased proofreading efficiency. Streptomycin, which stimulates error production by blocking proofreading in vitro, did not increase efficiency of suppressor tRNAs in strains with normal or streptomycin-resistant (rpsL) ribosomes. It did so only in combination with one rpsL mutation which is associated with streptomycin pseudodependence.
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| 4. |
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| 5. |
- Ny, Tor, et al.
(författare)
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Cloning and restriction mapping of the trmA gene coding for transfer ribonucleic acid (5-methyluridine)-methyltransferase in Escherichia coli K-12.
- 1980
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 142:2, s. 371-9
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid plasmid from the Clarke and Carbon collection has been isolated. This plasmid carries the trmA gene of E. coli, which is necessary for the formation of 5-methyluridine (m5U,ribothymidine) present in all transfer ribonucleic acid (tRNA) chains of the organism so far sequenced. A restriction map of the argCBH-trmA regions is presented. By using cloning in vitro, the trmA gene was located on a 2.9-kilobase pair deoxyribonucleic acid (DNA) fragment. These results and comparison with lambda dargECBH transducing phages established the gene order: argECBH trmA bfe in the 88-min region of the E. coli chromosomal map. Plasmids carrying this 2.9-kilobase pair DNA fragment overproduce the enzyme tRNA(m5U)methyltransferase (EC 2.1.1.35) 20 to 40 times. When this 2.9-kilobase pair chromosomal DNA fragment was expressed in a minicell system, a polypeptide of a molecular weight of 42,000 was synthesized. This polypeptide was tentatively identified as the tRNA(m5U)methyltransferase. These results support the earlier suggestion that the trmA gene is the structural gene for the tRNA(m5U)methyltransferase.
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| 6. |
- Ny, Tor, et al.
(författare)
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Growth rate-dependent regulation of transfer ribonucleic acid (5-methyluridine) methyltransferase in Escherichia coli B/r.
- 1980
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Ingår i: Journal of Bacteriology. - 0021-9193 .- 1098-5530. ; 141:1, s. 67-73
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Tidskriftsartikel (refereegranskat)abstract
- Enzymes catalyzing the transfer of methyl groups from S-adenosyl-l-methionine to a precursor transfer ribonucleic acid (tRNA) and forming 5-methyluridine (m(5)U), 1-methylguanine (m(1)G), or 5-methylaminomethyl-2-thio-uridine (mam(5)s(2)U) are denoted tRNA(m(5)U)-(EC 2.1.1.35), tRNA(m(1)G)-(EC 2.1.1.31), and tRNA(mam(5)s(2)U)methyltransferase. We have studied the regulation of these tRNA biosynthetic enzymes in Escherichia coli under various physiological conditions and in bacterial mutants known to affect the regulation of components of the translational apparatus. Such studies have revealed that tRNA(m(5)U)-methyltransferase increases with the growth rate in the same fashion as stable RNA, whereas the activity of two other tRNA methyltransferases remains constant in relation to the growth rate. Thus, these tRNA biosynthetic enzymes were not coordinately regulated. Regulation of both tRNA(m(5)U)methyltransferase and stable RNA was similar during shift-up and shift-down experiments. This enzyme showed a stringent regulation in relA(+) strain (T. Ny and G. R. Björk, J. Bacteriol. 130:635-641, 1977) but also in two temperature-sensitive mutants, fusA and fusB, known to influence the accumulation of guanosine 5'-diphosphate 3'-diphosphate and RNA synthesis at nonpermissive temperatures. The tRNA(m(5)U)methyltransferase showed a gene dose effect when its structural gene, trmA, was carried on a plasmid or on lambda transducing phages. Although the regulation of tRNA-(m(5)U)methyltransferase was surprisingly coupled to that of stable RNA, this enzyme was expressed at a much lower level.
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