scholarly journals Artificially induced active transport of amino acid driven by the efflux of a sugar via a heterologous transport system in de-energized Escherichia coli

1979 ◽  
Vol 178 (1) ◽  
pp. 103-107 ◽  
Author(s):  
M Bentaboulet ◽  
A Robin ◽  
A Kepes
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Active Transport ◽  
Transport System ◽  
Coupling Efficiency ◽  
Amino Acid Uptake ◽  
Energy Sources ◽  
Acid Uptake ◽  
Complex Sequence ◽  
The Poor

Consistent with the model of an H+ cotransport, amino acid uptake can be driven by a proton gradient generated by an efflux of sugar when the normal energy sources are suppressed. Heterologous countertransport is completely inhibited by uncouplers unlike homologous countertransport. Positive coupling was obtained with methyl thiogalactoside/proline, methyl thiogalactoside/phenylalanine, gluconate/proline; however, the poor coupling efficiency suggests a more complex sequence of reactions.

Active Transport of α-Aminoisobutyric Acid by the Isolated Midgut of Hyalophora Cecropia

1972 ◽  
Vol 56 (1) ◽  
pp. 167-172
Author(s):  
SIGNE NEDERGAARD
Keyword(s):  
Amino Acid ◽  
Active Transport ◽  
Opposite Direction ◽  
Amino Acid Transport ◽  
Amino Acid Uptake ◽  
Acid Uptake ◽  
Acid Transport ◽  
Active Process ◽  
Aminoisobutyric Acid ◽  
Amino Acid Flux

1. The α-aminoisobutyric acid flux from lumen to blood of the isolated Cecropia midgut is around 17 µmole/h, while the amino acid flux in the opposite direction is on average 0.3 µmole/h. 2. The amino acid uptake is inhibited by lack of oxygen. It is suggested that the amino acid transport from lumen to blood is an active process. 3. The amino acid uptake is inhibited by short-circuiting the midgut potential, indicating that there is no direct correlation between the active transport of potassium and the uptake of the amino acid by the midgut.

Amino Acid Uptake by Amino Acid Analog Resistant Tobacco Cell Lines

1978 ◽  
Vol 33 (9-10) ◽  
pp. 634-640 ◽  
Author(s):  
Jochen Berlin ◽  
Jade M. Widholm
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Transport System ◽  
Amino Acid Uptake ◽  
Resistant Cell ◽  
Resistant Cell Line ◽  
Acid Uptake ◽  
Wild Type ◽  
Phenylalanine Transport

Abstract Two tobacco cell lines resistant to p-fiuorophenylalanine (PFP) and one resistant to 5-methyltryptophan (5-MT) are compared with wild type cells in their ability to absorb amino acids from the medium. One p-fluorophenylalanine-resistant cell line shows greatly reduced uptake of all amino acids so is resistant to growth inhibition by other amino acid analogs. The impaired absorption is noted with amino acids, amino acid analogs and shikimate, but not with cinnamate, salicylate, nicotine, glucose, 3-O-methylglucose and palmitate. The phenylalanine transport system of the PFP-resistant cell line and the wild type both have Km values of 90 µᴍ, but have different V max values. Several analogs of phenylalanine and several neutral L-amino acids inhibit the phenylalanine transport system, while ʟ-aspartic acid, ʟ-arginine, ᴅ-phenylalanine or chlorogenic acid do not interfere with the ʟ-phenylalanine uptake. The results indicate the presence of more than one transport system for amino acid uptake. The lessened uptake of all amino acids, the specificity of the uptake systems and the unchanged binding let us conclude that a pleiotropic mutation or that some inhibitor causes the reduced uptake of all amino acids by the PFP-resistant cell line.

scholarly journals Global Regulatory Mutations in csrA andrpoS Cause Severe Central Carbon Stress in Escherichia coli in the Presence of Acetate

2000 ◽  
Vol 182 (6) ◽  
pp. 1632-1640 ◽  
Author(s):  
Bangdong Wei ◽  
Sooan Shin ◽  
David LaPorte ◽  
Alan J. Wolfe ◽  
Tony Romeo
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Rna Binding ◽  
Isocitrate Lyase ◽  
Tca Cycle ◽  
Amino Acid Uptake ◽  
Acetate Metabolism ◽  
Acid Uptake ◽  
Central Carbon ◽  
Glycogen Biosynthesis

ABSTRACT The csrA gene encodes a small RNA-binding protein, which acts as a global regulator in Escherichia coli and other bacteria (T. Romeo, Mol. Microbiol. 29:1321–1330, 1998). Its key regulatory role in central carbon metabolism, both as an activator of glycolysis and as a potent repressor of glycogen biosynthesis and gluconeogenesis, prompted us to examine the involvement ofcsrA in acetate metabolism and the tricarboxylic acid (TCA) cycle. We found that growth of csrA rpoS mutant strains was very poor on acetate as a sole carbon source. Surprisingly, growth also was inhibited specifically by the addition of modest amounts of acetate to rich media (e.g., tryptone broth). Cultures grown in the presence of ≥25 mM acetate consisted substantially of glycogen biosynthesis (glg) mutants, which were no longer inhibited by acetate. Several classes of glgmutations were mapped to known and novel loci. Several hypotheses were examined to provide further insight into the effects of acetate on growth and metabolism in these strains. We determined thatcsrA positively regulates acs(acetyl-coenzyme A synthetase; Acs) expression and isocitrate lyase activity without affecting key TCA cycle enzymes or phosphotransacetylase. TCA cycle intermediates or pyruvate, but not glucose, galactose, or glycerol, restored growth and prevented theglg mutations in the presence of acetate. Furthermore, amino acid uptake was inhibited by acetate specifically in thecsrA rpoS strain. We conclude that central carbon flux imbalance, inhibition of amino acid uptake, and a deficiency in acetate metabolism apparently are combined to cause metabolic stress by depleting the TCA cycle.

scholarly journals Radiation Inhibition of Amino Acid Uptake by Escherichia coli

1961 ◽  
Vol 1 (4) ◽  
pp. 265-277 ◽  
Author(s):  
E.S. Kempner ◽  
E.C. Pollard
Keyword(s):  
Escherichia Coli ◽  
Amino Acid ◽  
Amino Acid Uptake ◽  
Acid Uptake

scholarly journals Evidence that cycloleucine affects the high-affinity systems of amino acid uptake in cultured human fibroblasts

1984 ◽  
Vol 224 (1) ◽  
pp. 309-315 ◽  
Author(s):  
M Feneant ◽  
N Moatti ◽  
J Maccario ◽  
M Gautier ◽  
S Guerroui ◽  
...  
Keyword(s):  
Amino Acid ◽  
Transport System ◽  
Human Fibroblasts ◽  
Diffusion Constant ◽  
Amino Acid Uptake ◽  
Cell Uptake ◽  
Transport Systems ◽  
Acid Uptake ◽  
High Affinity ◽  
Cultured Human Fibroblasts

The influence of cycloleucine on kinetic parameters of uptake of L-alanine, L-proline and L-leucine into cultured human fibroblasts was examined under initial-rate conditions with substrate concentrations of 0.05-10 mM and 5 mM-cycloleucine. Kinetic data obtained by computer analysis showed that, in the absence of cycloleucine, cell uptake was heterogeneous for each amino acid. L-Alanine and L-leucine entered by two transport systems with different affinities; L-proline was taken up by one saturable transport system plus a diffusion-like process. This heterogeneity disappeared in the presence of cycloleucine, since the high-affinity systems were no longer detectable. The remaining process had the same kinetic constants as the low-affinity system for alanine and leucine and a KD similar to the diffusion constant for proline. The influence of cycloleucine on the amino acid uptake was not specific either to the amino acid concerned or to a particular transport system, since the three neutral amino acid-transport systems, A, ASC and L, were involved in these experiments. This influence was shown to be unaffected by the absence of Na+ (for leucine uptake). ATP content of the cells was identical in the presence or in the absence of cycloleucine.

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