The action of tributyltin chloride on the uptake of proline and glutamine by intact cells of Escherichia coli

1979 ◽  
Vol 57 (12) ◽  
pp. 1376-1383 ◽  
Author(s):  
A. P. Singh ◽  
P. D. Bragg
Keyword(s):  
Escherichia Coli ◽  
Amino Acids ◽  
Lipoic Acid ◽  
Membrane Vesicles ◽  
Electrochemical Gradient ◽  
Intact Cells ◽  
Iodide Ions ◽  
Tributyltin Chloride ◽  
Anion Exchange Reaction ◽  
Glutamine Uptake

Tributyltin chloride inhibits growth and uptake of glutamine and proline into intact cells of Escherichia coli. It causes efflux of the accumulated amino acids. A pH gradient generated in intact cells and everted membrane vesicles is dissipated by this compound. These effects do not require lipoic acid but are dependent on the presence of chloride, bromide, or iodide ions. We conclude that tributyltin chloride can catalyse a transmembrane OH−–anion exchange reaction and that this is its mode of inhibition of the uptake of these amino acids. The response of proline and glutamine uptake to the inhibitor is similar and is consistent with the transport of both amino acids requiring an electrochemical gradient of protons.

scholarly journals Energization of the transport systems for arabinose and comparison with galactose transport in Escherichia coli

1981 ◽  
Vol 200 (3) ◽  
pp. 611-627 ◽  
Author(s):  
K R Daruwalla ◽  
A T Paxton ◽  
P J Henderson
Keyword(s):  
Escherichia Coli ◽  
Transport System ◽  
Membrane Vesicles ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Protonmotive Force ◽  
Alkaline Ph ◽  
Ph Change ◽  
Intact Cells ◽  
Membrane Bound

1. Strains of Escherichia coli were obtained containing either the AraE or the AraF transport system for arabinose. AraE+,AraF- strains effected energized accumulation and displayed an arabinose-evoked alkaline pH change indicative of arabinose-H+ symport. In contrast, AraE-,AraF+ strains accumulated arabinose but did not display H+ symport. 2. The ability of different sugars and their derivatives to elicit sugar-H+ symport in AraE+ strains was examined. Only L-arabinose and D-fucose were good substrates, and arabinose was the only inducer. 3. Membrane vesicles prepared from an AraE+,AraF+ strain accumulated the sugar, energized most efficiently by the respiratory substrates ascorbate + phenazine methosulphate. Addition of arabinose or fucose to an anaerobic suspension of membrane vesicles caused an alkaline pH change indicative or sugar-H+ symport on the membrane-bound transport system. 4. Kinetic studies and the effects of arsenate and uncoupling agents in intact cells and membrane vesicles gave further evidence that AraE is a low-affinity membrane-bound sugar-H+ symport system and that AraF is a binding-protein-dependent high-affinity system that does not require a transmembrane protonmotive force for energization. 5. The interpretation of these results is that arabinose transport into E. coli is energized by an electrochemical gradient of protons (AraE system) or by phosphate bond energy (AraF system). 6. In batch cultures the rates of growth and carbon cell yields on arabinose were lower in AraE-,AraF+ strains than in AraE+,AraF- or AraE+,AraF+ strains. The AraF system was more susceptible to catabolite repression than was the AraE system. 7. The properties of the two transport systems for arabinose are compared with those of the genetically and biochemically distinct transport systems for galactose, GalP and MglP. It appears that AraE is analogous to GalP, and AraF to MglP.

scholarly journals Transport of l-glutamine and l-glutamate across sinusoidal membranes of rat liver. Effects of starvation, diabetes and corticosteroid treatment

1992 ◽  
Vol 284 (2) ◽  
pp. 333-340 ◽  
Author(s):  
S Y Low ◽  
P M Taylor ◽  
H S Hundal ◽  
C I Pogson ◽  
M J Rennie
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamate Uptake ◽  
Membrane Vesicles ◽  
Corticosteroid Treatment ◽  
Functional Expression ◽  
Liver Membrane ◽  
Health And Disease ◽  
Dependent Transport ◽  
Glutamine Uptake

There is increasing evidence that membrane transporters for glutamine and glutamate are involved in control of liver metabolism in health and disease. We therefore investigated the effects of three catabolic states [starvation (60 h), diabetes (4 days after streptozotocin treatment) and corticosteroid (8-day dexamethasone) treatment] associated with altered hepatic amino acid metabolism on the activity of glutamine and glutamate transporters in sinusoidal membrane vesicles from livers of treated rats. In control preparations, L-[14C]glutamine uptake was largely Na(+)-dependent, but L-[14C]glutamate uptake was largely Na(+)-independent. Vmax. values for Na(+)-dependent uptake of glutamine and/or glutamate exceeded control values (by about 2- and 12-fold respectively) in liver membrane vesicles from starved (glutamine), diabetic (glutamate) or steroid-treated (glutamine and glutamate) rats. The Km values for Na(+)-dependent transport of glutamine or glutamate and the rates of their Na(+)-independent uptake were not significantly altered by any treatment. Na(+)-independent glutamate uptake appeared to include a dicarboxylate-exchange component. The patterns of inhibition of glutamine and glutamate uptake by other amino acids indicated that the apparent induction of Na(+)-dependent amino acid transport in catabolic states included increased functional expression of systems A, N (both for glutamine) and X-ag (for glutamate). The results demonstrate that conditions resulting in increased secretion of catabolic hormones (e.g. corticosteroid, glucagon) are associated with increased capacity for Na(+)-dependent transport of amino acids into liver cells from the blood. The modulation of hepatic permeability to glutamine and glutamate in these situations may control the availability of amino acids for intrahepatic metabolic processes such as ureagenesis, ammonia detoxification and gluconeogenesis.

Characterization of Na(+)-independent glutamine transport in rat liver

1993 ◽  
Vol 265 (1) ◽  
pp. G90-G98 ◽  
Author(s):  
A. J. Pacitti ◽  
Y. Inoue ◽  
W. W. Souba
Keyword(s):  
Amino Acids ◽  
Rat Liver ◽  
Ph Dependence ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Charged Amino Acids ◽  
Amino Acids Transport ◽  
System L ◽  
Glutamine Transport ◽  
Glutamine Uptake

In hepatic plasma membrane vesicles (HPMVs) from rat liver, we observed that approximately 40-45% of Na(+)-independent glutamine uptake occurs by a saturable carrier-mediated process. This component of glutamine uptake is mediated by a transport agency distinct from that of previously described systems for the Na(+)-independent transport of amino acids. Transport of glutamine was electroneutral and occurred into an osmotically active space with negligible membrane binding. The model system L substrate 2-amino-2-norbornane-carboxylic acid (BCH) showed no appreciable inhibition of Na(+)-independent glutamine uptake by HPMVs but effectively inhibited the uptake of leucine, a classic system L substrate, in identical vesicle preparations. Further evidence against system L-mediated glutamine transport was provided by the pH dependence and the lack of trans-stimulation of saturable uptake. Competition experiments with selected amino acids revealed a pattern of inhibition of glutamine transport that was inconsistent with assignment of glutamine entry to systems asc, T, or systems for the Na(+)-independent transport of the charged amino acids. This BCH-noninhibitable transport system in HPMVs was highly selective for glutamine, histidine, and, to a lesser extent, asparagine. Inhibition of Na(+)-independent glutamine transport by leucine was noncompetitive in nature. On the basis of Na+ independence, pH sensitivity, absence of trans-stimulation, and an amino acid selectivity similar to that of the previously described hepatic Na(+)-dependent system N, we have provisionally designated the glutamine transport agency described in this article as system "n."

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