Characteristics of the active transport of peptides and amino acids by germinating barley embryos

Planta ◽  
1984 ◽  
Vol 162 (2) ◽  
pp. 159-165 ◽  
Author(s):  
D. J. Walker-Smith ◽  
J. W. Payne
Keyword(s):  
Amino Acids ◽  
Active Transport

scholarly journals New Plasmid System To Select forSaccharomyces cerevisiae Purine-Cytosine Permease Affinity Mutants

2001 ◽  
Vol 183 (14) ◽  
pp. 4386-4388 ◽  
Author(s):  
Renaud Wagner ◽  
Marie-Laure Straub ◽  
Jean-Luc Souciet ◽  
Serge Potier ◽  
Jacky de Montigny
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Structure Function ◽  
Active Transport ◽  
Function Model

ABSTRACT The FCY2 gene of Saccharomyces cerevisiaeencodes a purine-cytosine permease (PCP) that mediates the active transport of purines and cytosine. A structure-function model for this PCP has been recently proposed. In this study, we developed a plasmid-based system that generated a number of affinity-mutated alleles, enabling us to define new amino acids critical for permease function.

Tertiary active transport of amino acids reconstituted by coexpression of System A and L transporters in Xenopus oocytes

2009 ◽  
Vol 297 (3) ◽  
pp. E822-E829 ◽  
Author(s):  
Fiona E. Baird ◽  
Kevin J. Bett ◽  
Catherine MacLean ◽  
Andrew R. Tee ◽  
Harinder S. Hundal ◽  
...  
Keyword(s):  
Amino Acids ◽  
Active Transport ◽  
Xenopus Oocytes ◽  
Plasma Concentrations ◽  
Transport Systems ◽  
Functional Coupling ◽  
Specific System ◽  
Tor Pathway ◽  
System A ◽  
System L

The System L transporter facilitates cellular import of large neutral amino acids (AAs) such as Leu, a potent activator of the intracellular target of rapamycin (TOR) pathway, which signals for cell growth. System L is an AA exchanger, proposed to accumulate certain AAs by coupling to dissipation of concentration gradient(s) of exchange substrates generated by secondary active AA transporters such as System A (SNAT2). We addressed the hypothesis that this type of coupling (termed tertiary active transport) acts as an indirect mechanism to extend the range of AA stimulating TOR to those transported by both Systems A and L (e.g., Gln) through downstream enhancement of Leu accumulation. System A overexpression enabled Xenopus oocytes to accumulate substrate AAs (notably Ser, Gln, Ala, Pro, Met; totaling 2.6 nmol/oocyte) from medium containing a physiological AA mixture at plasma concentrations. Net accumulation of System L (4F2hc-xLAT1) substrates from this medium by System L-overexpressing oocytes was increased by 90% (from 0.7 to 1.35 nmol/oocyte; mainly Leu, Ile) when Systems A and L were coexpressed, coincident with a decline in accumulation of specific System A substrates (Gln, Ser, Met), as expected if the latter were also System L substrates and functional coupling of the transport Systems occurred. AA flux coupling was confirmed as trans-stimulation of Leu influx in System L-expressing oocytes by Gln injection (0.5 nmol/oocyte). The observed changes in Leu accumulation are sufficient to activate the TOR pathway in oocytes, although intracellular AA metabolism limits the potential for AA accumulation by tertiary active transport in this system.

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