Constitutive Ion Fluxes and Substrate Binding Domains of Human Glutamate Transporters
Application of L-glutamate activates ionic currents in voltage-clamped Xenopus oocytes expressing cloned human excitatory amino acid transporters (EAATs). However, even in the absence of L-glutamate, the membrane conductance of oocytes expressing EAAT1 was significantly increased relative to oocytes...
Saved in:
Published in: | The Journal of biological chemistry 1995-07, Vol.270 (30), p.17668-17671 |
---|---|
Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | Application of L-glutamate activates ionic currents in voltage-clamped Xenopus oocytes expressing cloned human excitatory amino acid transporters (EAATs). However, even in the absence of L-glutamate,
the membrane conductance of oocytes expressing EAAT1 was significantly increased relative to oocytes expressing EAAT2 or control
oocytes. Whereas transport mediated by EAAT2 is blocked by the non-transported competitive glutamate analog kainate ( K = 14 μM), EAAT1 is relatively insensitive ( K > 3 mM). Substitution of a block of 76 residues from EAAT2 into EAAT1, in which 18 residues varied from EAAT1, conferred
high affinity kainate binding to EAAT1, and application of kainate to oocytes expressing the chimeric transporter blocked
a pre-existing monovalent cation conductance that displayed a permeability sequence K > Na > Li choline . The results identify a structural domain of glutamate transporters that influences kainate binding and demonstrate the presence
of a constitutive ion-selective pore in the transporter. |
---|---|
ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.270.30.17668 |