scholarly journals Characteristics of the Amino Acid Transport System in the Mucosal Border of Rabbit Ileum

1970 ◽  
Vol 56 (6) ◽  
pp. 673-691 ◽  
Author(s):  
Jean Jacques Hajjar ◽  
Peter F. Curran
Keyword(s):  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Sodium Ion ◽  
Side Chain ◽  
Carboxyl Group ◽  
Acid Transport ◽  
Rabbit Ileum ◽  
Amino Acid Transport System ◽  
Amino Acid Analogues

The specificity of the neutral amino acid transport system in the brush border was examined by studying the ability of amino acid analogues to inhibit the unidirectional influx of phenylalanine from mucosal solution into the cells. Effects were evaluated in terms of the affinity of various substrates for the amino acid site in the transport system. The affinity of amino acids for the site was proportional to the number of carbon atoms in the side chain. Electron-withdrawing substituents in the ring of phenylalanine increased affinity and electron-releasing groups decreased affinity. Removal of the α-amino group from phenylalanine decreased affinity by a factor of approximately 50 and removal of the carboxyl group decreased affinity 12-fold. Effects on affinity of variations in the side chain of the amino acid can be comparable in magnitude to that of the carboxyl group. The effect of sodium ion on the transport system appears to be similar for all compounds tested.

scholarly journals Structure-Affinity Relationships of Substrates for the Neutral Amino Acid Transport System in Rabbit Ileum

1974 ◽  
Vol 64 (4) ◽  
pp. 443-467 ◽  
Author(s):  
Robert L. Preston ◽  
John F. Schaeffer ◽  
Peter F. Curran
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Neutral Amino Acid ◽  
Side Chain ◽  
Amino Group ◽  
Acid Transport ◽  
Binding Region ◽  
Rabbit Ileum ◽  
Amino Acid Transport System ◽  
Linear Portion

The apparent affinities of various amino acids for the neutral amino acid transport system in rabbit ileum were determined by measuring the inhibition of L-methionine-14C influx across the brush border membrane. The apparent affinity was very low for compounds lacking an α-amino group, compounds with the α-hydrogen substituted by a methyl group, D-compounds, compounds with tertiary branching in the side chain, compounds with either a positive or negative charge in the side chain, and in most cases, compounds with a hydrophilic moiety in the side chain. High apparent affinities were exhibited by compounds with unbranched carbon or carbon-sulfur side chains. Branched compounds such as valine and leucine exhibited affinities which correlate with binding of only the linear portion of the side chain. The calculated change in free energy of binding is 370 cal/mol/CH2 group which suggests the binding region for the side chain is partially hydrophobic. The affinities of families of analogues, derivatives of cysteine, methionine, serine, alanine, valine, and phenylalanine, correlate with their calculated octanol/water partition coefficients and are also correlated with apparent structural and electronic differences between families. The data permit a preliminary description of the functional geometry of the neutral amino acid transport site. The site contains a region for binding the α-amino group, α-carboxyl group, and side chain. The regions about the α-amino group and α-hydrogen are quite sterically limited. The side chain binding region is hydrophobic in nature and appears to be shallow, binding only the linear portion of branched or ring compounds.

Osmotic Regulation of ATA2 mRNA Expression and Amino Acid Transport System A Activity

2001 ◽  
Vol 283 (1) ◽  
pp. 174-178 ◽  
Author(s):  
Roberta R. Alfieri ◽  
Pier-Giorgio Petronini ◽  
Mara A. Bonelli ◽  
Alessandro E. Caccamo ◽  
Andrea Cavazzoni ◽  
...  
Keyword(s):  
Amino Acid ◽  
Mrna Expression ◽  
Transport System ◽  
Amino Acid Transport ◽  
Osmotic Regulation ◽  
Acid Transport ◽  
Amino Acid Transport System ◽  
System A

Expression and regulation of 4F2hc and hLAT1 in human trophoblasts

2002 ◽  
Vol 282 (1) ◽  
pp. C196-C204 ◽  
Author(s):  
Yoko Okamoto ◽  
Masahiro Sakata ◽  
Kazuhiro Ogura ◽  
Toshiya Yamamoto ◽  
Masaaki Yamaguchi ◽  
...  
Keyword(s):  
Amino Acid ◽  
Cell Line ◽  
Transport System ◽  
Human Placenta ◽  
Amino Acid Transport ◽  
Calcium Ionophore ◽  
Acid Transport ◽  
Amino Acid Transport System ◽  
System L ◽  
Choriocarcinoma Cell Line

The neutral amino acid transport system L is a sodium-independent transport system in human placenta and choriocarcinoma cells. Recently, it was found that the heterodimer composed of hLAT1 (a light-chain protein) and 4F2 heavy chain (4F2hc), a type II transmembrane glycoprotein, is responsible for system L amino acid transport. We found that the mRNAs of 4F2hc and hLAT1 were expressed in the human placenta and a human choriocarcinoma cell line. The levels of the 4F2hc and hLAT1 proteins in the human placenta increased at full term compared with those at midtrimester. Immunohistochemical data showed that these proteins were localized mainly in the placental apical membrane. Data from leucine uptake experiments, Northern blot analysis, and immunoblot analysis showed that this transport system was partially regulated by protein kinase C and calcium ionophore in the human choriocarcinoma cell line. Our results suggest that the heterodimer of 4F2hc and hLAT1 may play an important role in placental amino acid transport system L.

Cloning and functional characterization of a new subtype of the amino acid transport system N

2001 ◽  
Vol 281 (6) ◽  
pp. C1757-C1768 ◽  
Author(s):  
Takeo Nakanishi ◽  
Ramesh Kekuda ◽  
You-Jun Fei ◽  
Takahiro Hatanaka ◽  
Mitsuru Sugawara ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Mammalian Cells ◽  
Functional Characterization ◽  
Isobutyric Acid ◽  
Xenopus Laevis Oocytes ◽  
Acid Transport ◽  
Amino Acid Transport System

We have cloned a new subtype of the amino acid transport system N2 (SN2 or second subtype of system N) from rat brain. Rat SN2 consists of 471 amino acids and belongs to the recently identified glutamine transporter gene family that consists of system N and system A. Rat SN2 exhibits 63% identity with rat SN1. It also shows considerable sequence identity (50–56%) with the members of the amino acid transporter A subfamily. In the rat, SN2 mRNA is most abundant in the liver but is detectable in the brain, lung, stomach, kidney, testis, and spleen. When expressed in Xenopus laevis oocytes and in mammalian cells, rat SN2 mediates Na+-dependent transport of several neutral amino acids, including glycine, asparagine, alanine, serine, glutamine, and histidine. The transport process is electrogenic, Li+tolerant, and pH sensitive. The transport mechanism involves the influx of Na+ and amino acids coupled to the efflux of H+, resulting in intracellular alkalization. Proline, α-(methylamino)isobutyric acid, and anionic and cationic amino acids are not recognized by rat SN2.

scholarly journals The EGF Receptor Promotes the Malignant Potential of Glioma by Regulating Amino Acid Transport System xc(—)

2016 ◽  
Vol 76 (10) ◽  
pp. 2954-2963 ◽  
Author(s):  
Kenji Tsuchihashi ◽  
Shogo Okazaki ◽  
Mitsuyo Ohmura ◽  
Miyuki Ishikawa ◽  
Oltea Sampetrean ◽  
...  
Keyword(s):  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Egf Receptor ◽  
Malignant Potential ◽  
Acid Transport ◽  
Amino Acid Transport System
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