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Characterization of the replicon of plasmid pSW500 of Erwinia stewartii (1996)

Fu, Jen-Fen ; Chang, Han-Chang ; Chen, Yih-Ming ; [et al.]

Springer

Molecular genetics and genomics 250 (1996), S. 699-704

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ISSN: 1617-4623

Keywords: Key words Iteron ; Plasmid incompatibility ; Copy number control ; Replication protein ; Autoregulation

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A 1.6-kb DNA region required for the replication of pSW500 from Erwinia stewartii SW2 has been identified. DNA sequencing analysis revealed that this DNA fragment consists of a DnaA box, seven 16-bp direct repeats, and a 1005-bp open reading frame. The seven direct repeats have been demonstrated to mediate the incompatibility function of the plasmid. Primer extension analysis showed that the 1005-bp ORF is transcribed in vivo and the +1 site of the transcript is located 113 bp upstream from the translation initiation codon of the ORF. Complementation studies showed that this ORF is required for the replication of the plasmid and may encode a replication protein, RepA. Gene fusion studies revealed that the expression of repA is autoregulated by RepA. We also found that the pSW500 replicon has a copy number of approximately two and that the plasmid is stably maintained in Escherichia coli, thus demonstrating that the replicon contains all the elements required for copy number control and plasmid stability in E. coli. Curing of pSW500 from E. stewartii SW2 revealed that loss of pSW500 did not have any obvious effect on morphology or physiology of the cells, suggesting that pSW500 does not encode a function that is indispensable for the survival of the organism.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02172981

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Relationship of moleculated radical anion abundance and calculated lowest unoccupied molecular orbital energies for polychlorinated dibenzofurans and dibenzodioxins in electron capture negative ion mass spectrometry: Evidence for negative metastable ions (1988)

Laramée, J. A. ; Chang, Y-S. ; Arbogast, B. C. ; [et al.]

Chichester : Wiley-Blackwell

Biological Mass Spectrometry 17 (1988), S. 63-67

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ISSN: 1052-9306

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Relationships were found between experimentally measured molecular radical anion abundances and calculated lowest unoccupied molecular orbital energies (εLUMO) for polychlorodibenzofurans and polychlorodibenzo-p-dioxins. Anion abundances were measured using standard using standard mass spectrometric techniques, while εLUMO were calculated by the ‘Complete Neglect of Differential Overlap’ method. Polychlorodibenzofurans with calculated εLUMO ≥ 1.6 eV show 0% molecular radical anion and those with εLUMO ≤ 1.4 eV show ≥ 80% molecular radical anion abundance. Similarly, the molecular radical anion is absent for polychlorodibenzo-p-dioxins with calculated εLUMO ≥ 2.0 eV. A trend towards greater molecular radical ion relative abundance appears for 2.0 eV εLUMO ≥ 1.0 eV and a maximum is reached around 1 eV, whereupon the molecular ion abundance diminishes with lower εLUMO. B/E linked scan analysis indicates that chlorodioxins with εLUMO 〈 1 eV give increasing amounts of metastable anions.

Additional Material: 3 Ill.