scholarly journals Interactions between the thiol-group reagent N-ethylmaleimide and neutral and basic amino acid transporter-related amino acid transport

1999 ◽  
Vol 343 (1) ◽  
pp. 169-176 ◽  
Author(s):  
George J. PETER ◽  
Anthony DAVIES ◽  
Peter W. WATT ◽  
Jacqueline BIRRELL ◽  
Peter M. TAYLOR
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Basic Amino Acid ◽  
Thiol Group ◽  
Neutral Amino Acid ◽  
Acid Transport ◽  
Transport Activity ◽  
Direct Role ◽  
Cationic Amino Acid

The neutral and basic amino acid transport protein (NBAT) expressed in renal and jejunal brush-border membranes is involved in amino acid and cystine absorption. NBAT mutations result in Type 1 cystinuria. A C-terminal myc-tagged NBAT (NBATmyc) retains the amino acid transport and protein-protein interaction properties of NBAT when expressed in Xenopusoocytes. Neutral amino acid (Ala, Phe)-cationic amino acid (Arg) heteroexchanges related to NBATmyc expression in oocytes are inactivated by treatment with the thiol-group reagent N-ethylmaleimide (NEM), although significant Arg-Arg and Ala-Ala homoexchanges persist. Inactivation of heteroexchange activity by NEM is accompanied by loss of > 85% of alanine and cystine uptake, with smaller (< 50%) inhibition of arginine and phenylalanine uptake. NEM-sensitive cystine uptake and arginine-alanine heteroexchange (system b0,+ activity) are not expressed by an NBAT truncation mutant (NBATmyc-Sph1) lacking the 13 C-terminal amino acid residues, but the mutant expresses NEM-resistant transport activity (system y+L-like) equivalent to that of full-length NBATmyc. The deleted region of NBATmyc-Sph1 contains two cysteine residues (671/683) which may be the targets of NEM action. The synthetic amino acid 2-trifluoromethylhistidine (TFMH) stimulated alanine efflux at pH 7.5 and arginine at pH 5.5, but not vice versa, establishing the existence of distinct pathways for cationic and neutral amino acid homoexchange (TFMH is zwitterionic at pH 7.5 and cationic at pH 5.5). We suggest that NBAT expresses a combination of system b0,+ and y+L-like activities, possibly by interacting with different light-chain subunits endogenous to oocytes (as does the homologous 4F2hc protein). The C-terminus of NBAT may also have an additional, direct role in the mechanism of System b0,+ transport (the major transport activity that is defective in Type 1 cystinuria).

scholarly journals Electrogenic Na+-dependentl-alanine transport in the lizard duodenum. Involvement of systems A and ASC

2001 ◽  
Vol 280 (3) ◽  
pp. R612-R622
Author(s):  
Virtudes Medina ◽  
Antonio Lorenzo ◽  
Mario Dı́az
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Short Circuit ◽  
Duodenal Mucosa ◽  
Neutral Amino Acid ◽  
Acid Transport ◽  
Transport Activity ◽  
System A ◽  
Alanine Transport ◽  
Gallotia Galloti

l-Alanine transport across the isolated duodenal mucosa of the lizard Gallotia galloti has been studied in Ussing chambers under short-circuit conditions. Net l-alanine fluxes, transepithelial potential difference (PD), and short-circuit current ( Isc) showed concentration-dependent relationships. Na+-dependent l-alanine transport was substantially inhibited by the analog α-methyl aminoisobutyric acid (MeAIB). Likewise, MeAIB fluxes were completely inhibited byl-alanine, indicating the presence of system A for neutral amino acid transport. System A transport activity was electrogenic and exhibited hyperbolic relationships for net MeAIB fluxes, PD, and Isc, which displayed similar apparent K m values. Na+-dependentl-alanine transport, but not MeAIB transport, was partially inhibited by l-serine and l-cysteine, indicating the participation of system ASC. This transport activity represents the major pathway for l-alanine absorption and seemed to operate in an electroneutral mode with a negligible contribution to the l-alanine-induced electrogenicity. It is concluded from the present study that the active Na+-dependent l-alanine transport across the isolated duodenal mucosa of Gallotia galloti results from the independent activity of systems A and ASC for neutral amino acid transport.

scholarly journals Analysis of Cationic Amino Acid Transport Activity in Canine Lens Epithelial Cells

2013 ◽  
Vol 62 (4) ◽  
pp. 311-317 ◽  
Author(s):  
Hideharu Ochiai ◽  
Jun Moriyama ◽  
Nobuyuki Kanemaki ◽  
Reiichiro Sato ◽  
Ken Onda
Keyword(s):  
Amino Acid ◽  
Epithelial Cells ◽  
Amino Acid Transport ◽  
Lens Epithelial Cells ◽  
Acid Transport ◽  
Transport Activity ◽  
Cationic Amino Acid

scholarly journals Mutations of the basic amino acid transporter gene associated with cystinuria

1995 ◽  
Vol 310 (3) ◽  
pp. 951-955 ◽  
Author(s):  
K Miyamoto ◽  
K Katai ◽  
S Tatsumi ◽  
K Sone ◽  
H Segawa ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Transport ◽  
Basic Amino Acid ◽  
Amino Acid Transporter ◽  
Regulatory Subunit ◽  
Acid Transport ◽  
Transport Activity ◽  
Wild Type ◽  
Neutral Amino Acid Transporter ◽  
Acid Transporter

To investigate the function of a basic and neutral amino acid transporter-like protein (rBAT) which is a candidate gene for cystinuria, we analysed the rBAT gene in cystinuric patients. Patient 1 is a compound heterozygote with mutations in the rBAT gene causing a glutamine-to-lysine transition at amino acid 268, and a threonine-to-alanine transition at amino acid 341, who inherited these alleles from his mother (E268K) and father (T341A), respectively. Injection of T341A and E268K mutant cRNAs into oocytes decreased transport activity to 53.9% and 62.5% of control (L-cystine transport activity in oocytes injected with wild-type rBAT cRNA), respectively. Co-injection of E268K and T341A into oocytes strongly decreased amino acid transport activity to 28% of control. On the other hand, co-injection of wild-type and mutant rBAT did not decrease transport activity. Furthermore, immunological studies have demonstrated that the reduction of amino acid transport is not due to a decrease in the amount of rBAT protein expressed in oocyte membranes. These results indicate that mutations in the rBAT gene are crucial disease-causing lesions in cystinuria. In addition, co-injection experiments suggest that rBAT may function as a transport activator or regulatory subunit by homo- or hetero-multimer complex formation.

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