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  • 1
    Electronic Resource
    Electronic Resource
    Threonine diffusion and threonine transport in Corynebacterium glutamicum and their role in threonine production (1996)
    Springer
    Archives of microbiology 165 (1996), S. 48-54 
    Details
    ISSN: 1432-072X
    Keywords: Key words Amino acid transport ; Uptake ; Excretion ; Diffusion ; Threonine ; Corynebacterium glutamicum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transmembrane threonine fluxes (i.e., uptake, diffusion, and carrier-mediated excretion) all contribut-ing to threonine production by a recombinant strain of Corynebacterium glutamicum, were analyzed and quantitated. A threonine-uptake carrier that transports threonine in symport with sodium ions was identified. Under production conditions (i.e., when internal threonine is high), this uptake system catalyzed predominantly threonine/threonine exchange. Threonine export via the uptake system was excluded. Threonine efflux from the cells was shown to comprise both carrier-mediated excretion and passive diffusion. The latter process was analyzed after inhibition of all carrier-mediated fluxes. Threonine diffusion was found to proceed with a first-order rate constant of 0.003 min–1 or 0.004 μl min–1 (mg dry wt.)–1, which corresponds to a permeability of 8 × 10–10 cm s–1. According to this permeability, less than 10% of the efflux observed under optimal conditions takes place via diffusion, and more than 90% must result from the activity of the excretion carrier. In addition, the excretion carrier was identified by (1) inhibition of its activity by amino acid modifying reagents and (2) its dependence on metabolic energy in the form of the membrane potential. Activity of the excretion system depended on the membrane potential, but not on the presence of sodium ions. Threonine export in antiport against protons is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050295
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The mitochondrial dicarboxylate carrier is essential for the growth of Saccharomyces cerevisiae on ethanol or acetate as the sole carbon source (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The dicarboxylate carrier (DIC) is an integral membrane protein that catalyses a dicarboxylate–phosphate exchange across the inner mitochondrial membrane. We generated a yeast mutant lacking the gene for the DIC. The deletion mutant failed to grow on acetate or ethanol as sole carbon source but was viable on glucose, galactose, pyruvate, lactate and glycerol. The growth on ethanol or acetate was largely restored by the addition of low concentrations of aspartate, glutamate, fumarate, citrate, oxoglutarate, oxaloacetate and glucose, but not of succinate, leucine and lysine. The expression of the DIC gene in wild-type yeast was repressed in media containing ethanol or acetate with or without glycerol. These results indicate that the primary function of DIC is to transport cytoplasmic dicarboxylates into the mitochondrial matrix rather than to direct carbon flux to gluconeogenesis by exporting malate from the mitochondria. The ΔDIC mutant may serve as a convenient host for overexpression of DIC and for the demonstration of its correct targeting and assembly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01197.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Yeast Mitochondrial Carriers: Bacterial Expression, Biochemical Identification and Metabolic Significance (2000)
    Springer
    Journal of bioenergetics and biomembranes 32 (2000), S. 67-77 
    Details
    ISSN: 1573-6881
    Keywords: Mitochondria ; transport ; overexpression ; dicarboxylate carrier ; ACR1 gene ; succinate-fumarate exchange ; ARG11 gene; ornithine carrier ; arginine biosynthesis ; yeast ; metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The genome of Saccharomyces cerevisiae encodes 35 members of a family proteins thattransport metabolites and substrates across the inner membranes of mitochondria. They includethree isoforms of the ADP/ATP translocase and the phosphate and citrate carriers. At the startof our work, the functions of the remaining 30 members of the family were unknown. We areattempting to identify these 30 proteins by overexpression of the proteins in specially selectedhost strains of Escherichia coli that allow the carriers to accumulate at high levels in the formof inclusion bodies. The purified proteins are then reconstituted into proteoliposomes wheretheir transport properties are studied. Thus far, we have identified the dicarboxylate,succinate-fumarate and ornithine carriers. Bacterial overexpression and functional identification, togetherwith characterization of yeast knockout strains, has brought insight into the physiologicalsignificance of these transporters. The yeast dicarboxylate carrier sequence has been used toidentify the orthologous protein in Caenorhabditis elegans and, in turn, this latter sequencehas been used to establish the sequence of the human ortholog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005564429242
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    Paper (German National Licenses)
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