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Steady-state kinetic characterization of the mouse B0AT1 sodium-dependent neutral amino acid transporter


Camargo, Simone M R; Makrides, Victoria; Virkki, Leila V; Forster, Ian C; Verrey, François (2005). Steady-state kinetic characterization of the mouse B0AT1 sodium-dependent neutral amino acid transporter. Pflügers Archiv : European Journal of Physiology, 451(2):338-348.

Abstract

The members of the neurotransmitter transporter family SLC6A exhibit a high degree of structural homology; however differences arise in many aspects of their transport mechanisms. In this study we report that mouse B0AT1 (mouse Slc6a19) mediates the electrogenic transport of a broad range of neutral amino acids but not of the chemically similar substrates transported by other SLC6A family members. Cotransport of L-Leu and Na+ generates a saturable, reversible, inward current with Michaelis-Menten kinetics (Hill coefficient ~1) yielding a K0.5 for L-Leu of 1.16mM and for Na+ of 16mM at a holding potential of −50mV. Changing the membrane voltage influences both substrate binding and substrate translocation. Li+ can substitute partially for Na+ in the generation of L-Leu-evoked inward currents, whereas both Cl− and H+ concentrations influence its magnitude. The simultaneous measurement of charge translocation and L-Leu uptake in the same cell indicates that B0AT1 transports one Na+ per neutral amino acid. This appears to be accomplished by an ordered, simultaneous mechanism, with the amino acid binding prior to the Na+, followed by the simultaneous translocation of both co-substrates across the plasma membrane. From this kinetic analysis, we conclude that the relatively constant [Na+] along the renal proximal tubule both drives the uptake of neutral amino acids via B0AT1 thermodynamically and ensures that, upon binding, these are translocated efficiently into the cell

Abstract

The members of the neurotransmitter transporter family SLC6A exhibit a high degree of structural homology; however differences arise in many aspects of their transport mechanisms. In this study we report that mouse B0AT1 (mouse Slc6a19) mediates the electrogenic transport of a broad range of neutral amino acids but not of the chemically similar substrates transported by other SLC6A family members. Cotransport of L-Leu and Na+ generates a saturable, reversible, inward current with Michaelis-Menten kinetics (Hill coefficient ~1) yielding a K0.5 for L-Leu of 1.16mM and for Na+ of 16mM at a holding potential of −50mV. Changing the membrane voltage influences both substrate binding and substrate translocation. Li+ can substitute partially for Na+ in the generation of L-Leu-evoked inward currents, whereas both Cl− and H+ concentrations influence its magnitude. The simultaneous measurement of charge translocation and L-Leu uptake in the same cell indicates that B0AT1 transports one Na+ per neutral amino acid. This appears to be accomplished by an ordered, simultaneous mechanism, with the amino acid binding prior to the Na+, followed by the simultaneous translocation of both co-substrates across the plasma membrane. From this kinetic analysis, we conclude that the relatively constant [Na+] along the renal proximal tubule both drives the uptake of neutral amino acids via B0AT1 thermodynamically and ensures that, upon binding, these are translocated efficiently into the cell

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Item Type:Journal Article, refereed, original work
Communities & Collections:National licences > 142-005
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Scopus Subject Areas:Life Sciences > Physiology
Life Sciences > Clinical Biochemistry
Health Sciences > Physiology (medical)
Language:English
Date:1 November 2005
Deposited On:24 Oct 2018 13:42
Last Modified:31 Jul 2020 02:45
Publisher:Springer
ISSN:0031-6768
OA Status:Green
Publisher DOI:https://doi.org/10.1007/s00424-005-1455-x
Related URLs:https://www.swissbib.ch/Search/Results?lookfor=nationallicencespringer101007s004240051455x (Library Catalogue)

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