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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 402 (1982), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 13 (1982), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 75 (1990), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A Na+/H+ antiporter catalyses coupled Na+ extrusion and H+ uptake across the membranes of extremely alkalophilic bacilli. This exchange is electrogenic, with H+ translocated inward 〉 Na+ extruded. It is energized by the ??2 component of the ?μH+ that is established during primary proton pumping by the alkalophile respiratory chain complexes. These complexes abound in the membranes of extreme alkalophiles. Combined activity of the respiratory chain, the antiporter, and solute transport systems that are coupled to Na+ re-entry, allow the alkalophiles to maintain a cytoplasmic pH that is several pH units more acidic than optimal external pH values for growth. There is no compelling evidence for a specific and necessary role for any ion other than sodium in pH homeostasis, and although there is very high cytoplasmic buffering capacity in the alkaline range, active mechanisms for pH homeostasis are crucial. Energization of the antiporter as well as the proton translocating F1F0-ATPase that catalyses ATP synthesis in the extreme alkalophiles must accommodate the problem of the low net ?μH+ and the very low concentrations of protons, per se, in the external medium. This problem is by-passed by other bioenergetic work functions, such as solute uptake or motility, that utilize sodium ions for energy-coupling in the place of protons.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Members of the cation diffusion facilitator (CDF) family of membrane transport proteins are found in eukaryotes and prokaryotes. The family encompasses transporters of zinc ions, with cobalt, cad-mium and lead ions being additional substrates for some prokaryotic examples. No transport mechanism has previously been established for any CDF protein. It is shown here that the CzcD protein of Bacillus subtilis, a CDF protein, uses an antiporter mechanism, catalysing active efflux of Zn2+ in exchange for K+ and H+. The exchange is probably electroneutral, energized by the transmembrane pH gradient and oppositely oriented gradients of the other cation substrates. The data suggest that Co2+ and Cd2+ are additional cytoplasmic substrates for CzcD. A second product of the same operon that encodes czcD has sequence similarity to oxidoreductases and is here designated CzcO. CzcO modestly enhances the activity of CzcD but is not predicted to be an integral membrane protein and has no antiport activity of its own.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The stator-force generator that drives Na+-dependent motility in alkaliphilic Bacillus pseudofirmus OF4 is identified here as MotPS, MotAB-like proteins with genes that are downstream of the ccpA gene, which encodes a major regulator of carbon metabolism. B. pseudofirmus OF4 was only motile at pH values above 8. Disruption of motPS resulted in a non-motile phenotype, and motility was restored by transformation with a multicopy plasmid containing the motPS genes. Purified and reconstituted MotPS from B. pseudofirmus OF4 catalysed amiloride analogue-sensitive Na+ translocation. In contrast to B. pseudofirmus, Bacillus subtilis contains both MotAB and MotPS systems. The role of the motPS genes from B. subtilis in several motility-based behaviours was tested in isogenic strains with intact motAB and motPS loci, only one of the two mot systems or neither mot system. B. subtilis MotPS (BsMotPS) supported Na+-stimulated motility, chemotaxis on soft agar surfaces and biofilm formation, especially after selection of an up-motile variant. BsMotPS also supported motility in agar soft plugs immersed in liquid; motility was completely inhibited by an amiloride analogue. BsMotPS did not support surfactin-dependent swarming on higher concentration agar surfaces. These results indicate that BsMotPS contributes to biofilm formation and motility on soft agar, but not to swarming, in laboratory strains of B. subtilis in which MotAB is the dominant stator-force generator. BsMotPS could potentially be dominant for motility in B. subtilis variants that arise in particular niches.
    Type of Medium: Electronic Resource
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