Amino Acid Uptake by Pea Leaf Fragments

Cheung, Yuk-Ngai Stephen; Nobel, Park S.

doi:10.1104/pp.52.6.633

Cited by 31 publications

(15 citation statements)

References 15 publications

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“…The rates of transport over a wide concentration range do not conform to simple MichaelisMenten kinetics, resulting in various mechanistic interpretations (9,14,22). The energy dependence of transport is supported by the effects of metabolic inhibitors (4,9,14). The transport of small neutral amino acids is apparently mediated by a carrier with broad specificity (4, 9, 15); a number of other systems for basic, acidic, and neutral amino acids have been proposed (15).…”

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confidence: 99%

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Role of Calcium in Serine Transport into Tobacco Cells

Smith¹

1978

Plant Physiol.

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The transport of serie into tobacco (Nkodans tabscum L. var The transport of amino acids into plant cells has been investigated using either sections of plant drgans (4,22,25) or isolated cells cultured in liquid medium (9,10,14,15). Some generalizations can be drawn from the limited literature. The pH optimum for amino acid uptake is generally below 4.5 (9, 22) and transport may stimulate proton influx (25). The rates of transport over a wide concentration range do not conform to simple MichaelisMenten kinetics, resulting in various mechanistic interpretations (9,14,22). The energy dependence of transport is supported by the effects of metabolic inhibitors (4,9,14). The transport of small neutral amino acids is apparently mediated by a carrier with broad specificity (4, 9, 15); a number of other systems for basic, acidic, and neutral amino acids have been proposed (15). placed in a 125-ml Erlenmeyer flask containing 36 ml of 1% sucrose, 0.5 mm CaC12, and 5 mM bis-Tris-propane (pH 6.0).Transport was initiated by adding 4 ml of 1 mM L-[ 4C]serine (0.25 ACi), flasks were stoppered with cotton plugs and placed on a rotary shaker at 25 C for 1 hr. At the end of the experiment the cells were harvested by vacuum filtration, washed with 100 ml of 1 mM serine, placed in 10 ml of liquid scintillation fluid containing 1 ml of water, and radioactivity determined in a Packard 3310 Tri-Carb scintillation spectrometer with external standardization.Ca uptake/exchange was measured in a 125-ml Erlenmeyer flask containing 40 ml of 1% sucrose, 0.5 mM 45CaC12 (0.5 ,uCi), and 5 mrm bis-Tris-propane (pH 6.0).All operations before the addition of cells were conducted in a sterile room using sterilized media and equipment. RESULTS General Characteristics. A previous investigation of cysteine transport into these cells (9) established that transport was biphasic, inhibited by respiratory inhibitors (azide, 2,4-dinitrophenol, and carbonyl cyanide m-chlorophenylhydrazone) and sulfhydryl reagents (iodoacetamide and N-ethylmaleimide). The inhibition of cysteina transport by other amino acids supported the presence of a general transport system for neutral amino acids. The present study assumes that these observations are applicable to serine transport, however, none of the conclusions of this study are based on this assumption.Serine transport was linear with time for at least 2 hr and with amount of tissue in the range 0.15 to 0.5 g fresh weight. Serine uptake was not affected by increasing the sucrose concentration of the transport medium from 1 to 3%, however, a 25% reduction in rate was observed when the sucrose concentration was increased to 5%. Addition of B-5 growth medium to transport medium caused an inhibition of transport, as reported previously (9). The inhibitory constituents in B-5 medium were shown to be K+ (2.5 mM) and 2,4-D (4.5 uM). Transport rates were significantly higher in freshly transferred cells but were relatively constant during the exponential increase in culture fresh weight (Fig. 1). Serine transport...

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confidence: 99%

“…The transport of amino acids into plant cells has been investigated using either sections of plant drgans (4,22,25) or isolated cells cultured in liquid medium (9,10,14,15). Some generalizations can be drawn from the limited literature.…”

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confidence: 99%

Role of Calcium in Serine Transport into Tobacco Cells

Smith¹

1978

Plant Physiol.

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“…DISCUSSION The general characteristics of L-Arg, L-Asp, L-His, and L-Phe transport have been determined. In most respects, the transport of these amino acids is identical to that of L-Leu (4) and of other amino acids (7,8,10,15). That is, uptake is pH-dependent, energydependent, stereospecific, dependent upon culture growth phase, concentrative, and carrier-mediated, the exception being that LAsp is not concentrated.…”

Section: Resultsmentioning

confidence: 88%

“…Some researchers suggest a single system for all amino acids (6,7,10), while others suggest multiple systems (1,9,12). Cheung and Nobel (7) reported that L-Ala, L-Ser, L-Thr, L-Asp, and L-Glu competitively inhibited glycine uptake in pea leaf fragments and that Ki values were similar to Km values.…”

Section: Resultsmentioning

confidence: 99%

“…Our inhibition results demonstrated that the carrier system(s) which transports L-Arg, L-Asp, L-His, L-Leu, and L-Phe is either a common carrier system(s) where all amino acids bind to a common site for transport or a complex carrier system(s) where allosteric binding of one amino acid inhibits the binding or transport of another amino acid. We believe the former explanation to be the most reasonable, inasmuch as amino-acid inhibition has been shown to be competitive (6,7,10) and allosteric inhibition would require a far more complex molecular system(s). Thus, the simplest interpretation of the amino-acid inhibition data presented in this paper is that acidic (L-Asp), basic (L-Arg and L-His) and neutral (L-Leu and L-Phe) amino acids are transported into cultured tobacco cells by a single-carrier system.…”

Section: Resultsmentioning

confidence: 99%

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Amino Acid Transport in Suspension-Cultured Plant Cells

McDaniel

Holterman²,

Bone³

et al. 1982

Plant Physiol.

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The transport of L-agifife (L-Arg), L-aspartic acid (L-Asp), L-histldine (L-His), and L-phenylablni (L-Phe) has been investigated in suspension cultures of Nkotiana tabacum cv. Wisconsin 38 cells. Uptake of these amino acids is pH-and energy-dependent, concentrative (except for LAsp), stereospecific, dependent upon culture growth phase, and, apparently, carrier-mediated. A 1,000-fold higher concentration of L-leucine (L-Leu) can inhibit all of the energy-dependent uptake of L-Arg, L-Asp, L-His, and L-Phe. A 1,000-fold higher concentration of L-Arg or L-Phe can inhibit all of the energy-dePendent uptake of L-Leu. L-Asp and L-His cannot inhibit all of the energy-dependent L-Leu uptake. However, evidence is presented which indicates that L-Leu enters the cell via the carrier system which also transports L-Asp and L-His. These inhibition data are consistent with the hypothesis that all of these amino acids are transported by a single carder system.Plant cells take up amino acids from their external environment. This presumed membrane function has been examined in whole plants (5), excised organs (15), tissues (14), and cultured cells (12).However, the number of carrier systems involved in amino-acid uptake is not known for any plant cell, nor has any carrier system been fully characterized (4,6). We have begun to characterize the carrier system(s) which transports amino acids into suspensioncultured tobacco cells with the long-term goal ofisolating transport mutants. An assay for measuring amino acid transport has been developed (3), and various aspects of L-Leu transport, including kinetics and regulation, have been studied (2,4,13).The work reported here was undertaken to determine if structurally dissimilar amino acids are transported into suspensioncultured tobacco cells by the L-Leu carrier system. The evidence presented indicates that energy-dependent uptake ofL-Asp, L-Arg, L-His, L-Leu, and L-Phe into cultured tobacco cells is only by the L-Leu carmer system. MATERIALS AND METHODSCell Culture and Assay. Cell culture and assay procedures have been described (3,4 Wisc. 38 were maintained in 125-ml Erlenmeyer flasks containing 50 ml L and S medium.2 Cells were subcultured every 7 days by adding 50 ml of L and S medium to a 125-ml Erlenmeyer flask containing 50 ml of cell suspension in stationary phase and dividing the resulting suspension between two 125-ml flasks. The subculture inoculum size was about 9 g fresh weight, and, 4 days after subculturing, the cells had completed their period of rapid growth. Uptake rate was measured in growing cells (3 days after subculturing) over a 9-min period with four sample points in an incubation solution consisting of fresh L and S medium; unlabeled L-Arg, L-Asp, L-His, L-Leu, or L-Phe of various concentrations;Leu, or L-[alanine 2,3-3HjPhe. This 9-min assay measures initial uptake rates (3, 4) and was used in all experiments except those employed to measure amino-acid accumulation. Uptake rates are expressed as nmol/(ml HV .min), where HV is the volume of cell debr...

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Cell Electrophysiology and Membrane Transport

Bentrup¹

1982

Progress in Botany / Fortschritte Der Botanik

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Amino Acid Uptake by Pea Leaf Fragments

Cited by 31 publications

References 15 publications

Role of Calcium in Serine Transport into Tobacco Cells

Role of Calcium in Serine Transport into Tobacco Cells

Amino Acid Transport in Suspension-Cultured Plant Cells

Cell Electrophysiology and Membrane Transport

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