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  • 1
    ISSN: 1432-072X
    Keywords: Copper-limitation ; Escherichia coli ; Cytochrome oxidases ; Oxygen reduction ; Respiratory chains
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The role(s) of copper in a bacterial cytochrome oxidase of the aa 3-type was investigated by growth of Paracoccus denitrificans NCIB 8944, in batch and steady state continuous culture, in a medium from which the bulk of the copper had been extracted. In a medium containing approximately 0.02 μM copper, cellular copper content, cytochromes a+a 3 and cytochrome a 3 were reduced to 55%, 58% and 33% respectively of control values and there were also less marked decreases in cytochromes c+c 1 (to 85%) and a CO-binding b-type cytochrome, possibly cytochrome o (to 71%). Copper deficiency elicited in reduced minus oxidized difference spectra a shift to shorter wavelengths and narrowing of the band width of the α-band of the oxidase, and loss of a (negative) band near 830 nm attributable to CuA (the copper functionally associated with haem a in the oxidase complex). The oxidase in copper-deficient cells reacted with oxygen to form the oxy “Compound A” at rates similar to that in control cells but CO recombination to ferrous haem a 3 was slowed 4-fold in the copper deficient case. The results are interpreted as indicating loss of CuA and changes in the proportions of haems a and a 3 with retention of catalytic activity. Titrations of respiration rates with antimycin suggested that copper deficiency did not result in diversion of electron flux through an antimycin A-insensitive, cytochrome o-terminated branch of the respiratory chain.
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  • 2
    ISSN: 1432-072X
    Keywords: Iron-limitation ; Escherichia coli ; Respiratory chains ; Cytochromes ; Gallium ; Metal uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of iron limitation on growth, the composition and function of the respiratory chains, and gallium uptake inEscherichia coli have been studied. Decreasing the iron concentration in a defined medium using Chelex resin gave lower growth yields in both continuous culture and prolonged batch culture. In the former, ironlimited (entering [Fe]≤2.0 μM) cells exhibited diminished respiration rates, respiration-driven proton translocation quotients, and levels of non-haem iron and cytochromes. The cellular concentration of haemoproteinb-590 (a cytochromea 1-like hydroperoxidase) decreased 20-fold on iron limitation, whilst a CO-binding pigment with an absorption maximum in the dithionite-treated form near 500 nm appeared. Gallium(III) (9 μM) added to iron-limited, but not iron-sufficient, cultures diminished growth yields further; cells grown with low entering concentrations of iron took up less gallium than iron-sufficient cells. These results are attributed to the interference by gallium(III) with siderophore-mediated metal uptake. Gallium also stimulated iron uptake and was itself accumulated by iron-sufficient cells, suggesting that gallium(III) also affects the iron transport system(s) of low affinity.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 213 (1988), S. 99-104 
    ISSN: 1617-4623
    Keywords: Promoters ; Escherichia coli ; Proteus vulgaris ; Hemolysin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The hemolytic activity of Escherichia coli and Proteus vulgaris is determined by common contiguous genes encoding synthesis (hly C, hly A) and specific secretion (hly B, hly D) of active hemolysin. Nevertheless, the hlyC-proximal DNA sequences directing production of the homologous hemolysins by the recombinant DNAs P. vulgaris pVU763-709 and E. coli pANN202-312 showed no extensive homology. Primer extension and S1 nuclease protection were used to define in the two sequences the 5′ termini of hly transcripts synthesized in vivo and thus to infer the active hly promoters sequences. The E. coli hly C upstream region contained three separate promotors directing in vivo hly transcription, while the corresponding transcription of the P. vulgaris hly operon originated from a single distinct promotor, the-35 and-10 sequences of which formed part of an inverted repeat sequence. Elevated hemolytic activity caused by upstream Tn5 insertions in pVU763-709 resulted from increased transcription from this promotor.
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  • 4
    ISSN: 0173-0835
    Keywords: Two-dimensional polyacrylamide gel electrophoresis ; Escherichia coli ; SWISS-2DPAGE database ; Immobilized pH gradient ; Sequence tag ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The combination of two-dimensional polyacrylamide gel electrophoresis (2-DPAGE), computer image analysis and several protein identification techniques allowed the Escherichia coli SWISS-2DPAGE database to be established. This is part of the ExPASy molecular biology server accessible through the WWW at the URL address http://www.expasy.ch/ch2d/ch2d-top.html. Here we report recent progress in the development of the E. coli SWISS-2DPAGE database. Proteins were separated with immobilized pH gradients in the first dimension and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the second dimension. To increase the resolution of the separation and thus the number of identified proteins, a variety of wide and narrow range immobilized pH gradients were used in the first dimension. Micropreparative gels were electroblotted onto polyvinylidene difluoride membranes and spots were visualized by amido black staining. Protein identification techniques such as amino acid composition analysis, gel comparison and microsequencing were used, as well as a recently described Edman “sequence tag” approach. Some of the above identification techniques were coupled with database searching tools. Currently 231 polypeptides are identified on the E. coli SWISS-2DPAGE map: 64 have been identified by N-terminal microsequencing, 39 by amino acid composition, and 82 by sequence tag. Of 153 proteins putatively identified by gel comparison, 65 have been confirmed. Many proteins have been identified using more than one technique. Faster progress in the E. coli proteome project will now be possible with advances in biochemical methodology and with the completion of the entire E. coli genome.
    Additional Material: 4 Ill.
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  • 5
    ISSN: 0173-0835
    Keywords: Escherichia coli ; SWISS-2DPAGE database ; Two-dimensional polyacrylamide gel electrophoresis ; Immobilized pH gradients ; Protein pattern comparison ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Numerous Escherichia coli proteins have already been characterized by two-dimensional gel electrophoresis (2-D PAGE), using carrier ampholytes in the first dimension (VanBogelen, R. A., Sankar, P., Clark, R. L., Bogan, J. A. and Neidhardt, F. C., Electrophoresis 1992, 13, 1014-1054). We present here a reference protein map of E. coli obtained with immobilized pH gradients (IPG) and available in a SWISS-2DPAGE format. Out of the protein spots identified in the E. coli gene protein database by Neidhardt's group, 153 have been identified on the E.coli SWISS-2DPAGE database map by gel comparison and most of them were confirmed either by the analysis of amino acid composition (AAC) and/or N-terminal microsequencing. Additionally, five as yet unsequenced proteins were found. The E. coli SWISS-2DPAGE database is part of the ExPASy molecular biology server accessible through the Word Wide Web network.
    Additional Material: 3 Ill.
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