A model for the topology of excitatory amino acid transporters determined by the extracellular accessibility of substituted cysteines.
Excitatory amino acid transporters (EAATs) function as both substrate transporters and ligand-gated anion channels. Characterization of the transporter's general topology is the first requisite step in defining the structural bases for these distinct activities. While the first six hydrophobic domains can be readily modeled as conventional transmembrane segments, the organization of the C-terminal hydrophobic domains, which have been implicated in both substrate and ion interactions, has been controversial. Here, we report the results of a comprehensive evaluation of the C-terminal topology of EAAT1 determined by the chemical modification of introduced cysteine residues. Our data support a model in which two membrane-spanning domains flank a central region that is highly accessible to the extracellular milieu and contains at least one reentrant loop domain.
Seal
R P
RP
Vollum Institute, Oregon Health Sciences University, Portland 97201, USA.
Leighton
B H
BH
Amara
S G
SG
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000235:genetics*; D000595:Amino Acid Sequence; D027322:Amino Acid Transport System X-AG; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D001710:Biotin; D019556:COS Cells; D003545:Cysteine / Q000737:chemistry*; D005020:Ethyl Methanesulfonate / Q000031:analogs & derivatives; D005110:Extracellular Space / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007202:Indicators and Reagents; D015640:Ion Channel Gating / Q000502:physiology; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000502:physiology; D017434:Protein Structure, Tertiary
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D000596:Amino Acids; D007202:Indicators and Reagents; D008565:Membrane Proteins; C093171:methanethiosulfonate ethylammonium; D001710:Biotin; D005020:Ethyl Methanesulfonate; D003545:Cysteine