Maturation of membrane function: Transport of amino acid by rat erythroid cells

Wise, W. C.

doi:10.1002/jcp.1040870208

Cited by 34 publications

(9 citation statements)

References 11 publications

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“…Major alterations in membrane transport occur during this maturation process. Reticulocytes possess a Na+-dependent transport system for alanine and a-aminoisobutyric acid which disappears on cell maturation (5). Active transport of Na+ is also lower in mature erythrocytes compared with reticulocyte-rich populations (6), although cation inosine, hexokinase, and glucose-6-phosphate dehydrogenase were from Boehringer, Mannheim, W. Germany; iodoacetic acid and sodium iodoacetamide were from Eastman Kodak Co., Rochester, N. Y.; ATP, NADP+, and Tris-HCl were from Sigma Chemical Co., St. Louis, Mo.…”

Section: Introductionmentioning

confidence: 99%

“…[3H]-Ouabain, 5 Ci/mM ethanol-benzene solution, New England Nuclear lot no. 184-196, was evaporated to dryness under a stream of nitrogen and redissolved in 20-fold excess of unlabeled ouabain to give a stock solution of 10 juM ouabain in water of activity 12.5 ,ICi/ml.…”

Section: Introductionmentioning

confidence: 99%

“…This stock solution was stable at 4°C for several months. Silica crucibles (high-form, 5 High-reticuilocyte blood donors. Patients were selected with peripheral blood reticulocytosis of 2.0-25% resulting f'rom chronic autoimmune hemolytic anemia, pyruivate kinase deficiency hemolytic anemia, chronic gastrointestinal blood loss, or during hematinic therapy of' a deficiency anemia.…”

Section: Introductionmentioning

confidence: 99%

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Selective loss of calcium permeability on maturation of reticulocytes.

Wiley¹,

Shaller²

1977

J. Clin. Invest.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Selective loss of calcium permeability on maturation of reticulocytes.

Wiley¹,

Shaller²

1977

J. Clin. Invest.

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“…That system, ASC, differs from System A in its intolerance for an N-methyl group on the substrate, for branching of the sidechain, and for Li + as a substitute for Na + as co-substrate, It functions-in all the nucleated or reticulated red blood cells studied so far, as well as in the Ehrlich cell [2,9,11,15,18,19,20], in both erythroblastic and myeloblastic leukemia cells [Wise, personal communica-…”

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confidence: 99%

Na+/L+ selectivity in transport systemA: Effects of substrate structure

Christensen

Handlogten

1977

J. Membrain Biol.

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Summary. The effect of amino acid structure on the selectivity between Na and Li as co-substrates for transport System A in the Ehrlich cell has been explored to localize relative binding positions. By various tests the relative effectiveness of the two cations varies over fivefold. Changes in structure of the amino acid that lower its response to Na tend to decrease its selectivity for Na over Li, but with many exceptions. The higher the Li level required to half-maximize amino acid entry, the slower tends to be the entry attainable for both Li and amino acid. Our attention fell on strong departures from these trends. An atypically fast uptake is produced by Li in the presence of a second amino group pK~ <8.5, in exceptional association with the known fast uptake in Na. The hydroxyl group of serine yields exceptionally strong uptake, whereas hydroxyl groups in restrained orientation (as in threonine and hydroxyprolines) sharply limit co-substrate interaction. Despite the absence of a sidechain, glycine shows unexceptional relative co-substrate responses. A sidechain in the a 2 position, as in D-alanine, lowers tolerance for both ions, an aberration largely corrected by the insertion of a second (a~) methyl group, and surprisingly, even by an N-methyl group. For L-alanine, an N-methyl group has in contrast unfavorable effects on co-substrate interaction. These factors point to disturbance by the a 2 methyl group of the position taken by the amino acid at the site, largely rectifiable by balancing effects of a second methyl group. They also point to a position of the alkali ion quite close to the a-carbon and far from the position taken in System ASC.Addition of an ethylene bridge between the a-methyl groups of a(methylamino)-isobutyric acid leads to the strongest discrimination seen against Li § relative to Na § suggesting through crowding of the area that the alkali ion adjoins the three methyl groups of this analog.Only one of the Na +-dependent transport systems has so far revealed the spatial position taken by the sodium ion with respect to the substrate molecule at the receptor site. That system, ASC, differs from System A in its intolerance for an N-methyl group on the substrate, for branching of the sidechain, and for Li + as a substitute for Na + as co-substrate, It functions-in all the nucleated or reticulated red blood cells studied so far, as well as in the Ehrlich cell [2,9,11,15,18,19,20], in both erythroblastic and myeloblastic leukemia cells [Wise, personal communica-

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“…This quantitative difference may result from loss, with maturation, of transport systems (25), or may reflect the absence of folate utilization by mature erythrocytes. We favor the latter possibility because folate uptake in other cell types is clearly related to metabolic activity (3,23,26).…”

Section: Discussionmentioning

confidence: 99%

The Mechanism of 5-Methyltetrahydrofolate Transport by Human Erythrocytes

1978

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A B S T R A C T The mechanism involved inThus peripheral erythrocytes incorporate 5-methyltetrahydrofolate by a saturable, temperature-dependent, substrate-specific process which is influenced by counter-transport. This mechanism is qualitatively similar to the carrier-mediated transport of folate compounds previously described in other cell types. Therefore, human erythrocytes should be useful for detailed characterization of this membrane carrier system.

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Maturation of membrane function: Transport of amino acid by rat erythroid cells

Cited by 34 publications

References 11 publications

Selective loss of calcium permeability on maturation of reticulocytes.

Selective loss of calcium permeability on maturation of reticulocytes.

Na+/L+ selectivity in transport systemA: Effects of substrate structure

The Mechanism of 5-Methyltetrahydrofolate Transport by Human Erythrocytes

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