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  • 1
    Electronic Resource
    Electronic Resource
    Regulation of the chlA locus of Escherichia coli K12; involvement of molybdenum cofactor (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 5 (1991), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The chlA encodes functions required for the biosynthesis of the molybdopterin part of the molybdenum cofactor. Mutants, carrying gene fusions at the chlA locus, which place β-galactosidase expression under the control of the chlA promoter, have been isolated employing λ plac Mui as the mutagen. The mutants exhibited β-galactosidase expression which was greatly enhanced when grown anaerobically. Secondary mutations at the chlB, D, E or G loci did not affect the high level of expression. The fnr gene product was not required for the anaerobic expression. Bacteriophage λ transducing phages were isolated which carried the φ (chlA-lac) mutations and were used to construct chlA/φ (chlA-lac) merodiploids. The merodiploids exhibited a much lower level of expression but showed the same characteristics as strains carrying lac fusions to the single chromosomal chlA locus. Genetic evidence is presented which strongly suggests that the molybdenum cofactor is a repressor of chlA expression. The anerobic enhancement of chlA expression is mediated via a mechanism that is distinct from the molybdenum cofactor effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1991.tb00764.x
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  • 2
    Electronic Resource
    Electronic Resource
    Molybdenum cofactor requirement for in vitro activation of apo-molybdoenzymes of Escherichia coli (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 4 (1990), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The apo-nitrate reductase precursor in an Escherichia coli chiB mutant preparation obtained following growth in the presence of tungstate is activated by incubation with protein FA and a heat-treated preparation from an E. coli crude extract. We show that the requirement for heat-treated E. coli crude extract can be fulfilled by material obtained from either of two heat–denatured purified E. coli molybdoenzymes, namely nitrate reductase or trimethylamine N-oxide reductase. Apo-trimethylamine N-oxide reductase precursor in the tungstate-grown chIB preparation can be activated in a similar manner with material from either heat-denatured molybdoenzyme. The active component in the denatured molybdoenzyme preparations is shown to be the molybdenum cofactor by Neurospora crassa nit1 molybdenum cofactor assay, size estimation and fluorimetric analysis. The direct demonstration of the requirement for molybdenum cofactor in the E. coli tungstate-grown chIB complementation system is an important step towards the molecular definition of the activation process and an understanding of the mechanism of cofactor acquisition during molybdoenzyme biosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1990.tb00633.x
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  • 3
    Electronic Resource
    Electronic Resource
    Nickel deficiency gives rise to the defective hydrogenase phenotype of hydc and fnr mutants in Escherichia coli (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Hydrogenase activity and other hydrogenase-related functions can be restored to hydC mutants by the specific addition of nickel salts to the growth medium. These mutants are defective in all three hydrogenase isoenzymes and the restoration is dependent upon protein synthesis. The cellular nickel content of the mutant when grown in LB medium is less than 1% of that of the parental strain. Partial suppression of the hydrogenase phenotype of hydC mutants occurs when growth takes place in a different medium. This correlates with an increased cellular nickel content. The phenotype of the mutant is also fully suppressed by growth in media of very low magnesium content. Such media facilitate nickel uptake via the magnesium transport system, which leads to the acquisition of a normal cellular nickel content. Mutations in the fnr gene, which encodes a transcriptional regulator for several anaerobically expressed enzymes, abolishes hydC expression and gives rise to a defective hydrogenase phenotype. The hydrogenase phenotype of fnr is closely similar to that of hydC in all respects examined. The hydrogenase activity of fnr strains can be restored by the presence of a functional hydC gene on a multicopy plasmid. The hydrogenase phenotype of fnr strains therefore arises indirectly via suppression of hydC, which leads to a low cellular nickel content. Nickel has no influence on fumarate reductase or nitrate reductase activities in fnr strains. The hydrogen-metabolism phenotype of fnr strains is, therefore, dependent upon their ability to acquire nickel from growth media. It is likely that hydC encodes a specific transport system for nickel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00156.x
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  • 4
    Electronic Resource
    Electronic Resource
    Proposed nomenclature for the genes involved in molybdenum metabolism in Escherichia coli and Saimonella typhimurium (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 6 (1992), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1992.tb02215.x
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular genetic analysis of the moa operon of Escherichia coli K-12 required for molybdenum cofactor biosynthesis (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 8 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A 3.2 kb chromosomal DNA fragment which complements the defects in a series of twelve moa::Mucts insertion mutants has been sequenced. Five open reading frames (ORFs) were identified and these are arranged in a manner consistent with their forming an operon. The encoded proteins (MoaA-MoaE) have predicted molecular weights of 37346, 18665, 17234, 8843 and 16981 respectively. Examination of subclones of the whole locus in an expression system demonstrated the predicted products. N-terminal amino acid sequences for the moa A, B, C and E products confirmed the translational starts. Genetic analysis distinguished four classes of moa mutants corresponding to genes moaA, C, D and E. Potential promoter sequences upstream of moaA and a possible transcription termination signal have been identified. Genetic analysis of the chlA1 and chlM mutants, which have been biochemically characterized as defective in molybdopterin biosynthesis, indicates that these carry lesions in moaA and moaD respectively. The moa locus is orientated clockwise at 17.7 minutes in the chromosome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01652.x
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  • 6
    Electronic Resource
    Electronic Resource
    Two crystal forms of ModE, the molybdate-dependent transcriptional regulator from Escherichia coli (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 542-543 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The molybdenum-responsive ModE regulatory protein from Escherichia coli has been purified and used in crystallization trials. Two crystal forms have been observed. Form I is tetragonal, P41212 (or enantiomorph), with a = b = 72.3, c = 246.2 Å and diffracts to medium resolution. Form II is orthorhombic, P21212, with a = 82.8, b = 127.9, c = 64.0 Å and diffraction has been observed beyond 2.8 Å resolution. Structural analysis, in combination with ongoing biochemical characterization, will assist the elucidation of the structure–activity relationship in regulating the uptake of molybdate in bacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444998011354
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