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Identification of residues lining the entrance of the human serotonin transporter substrate permeation pathway using homology modeling
Author(s) -
TorresAltoro Melissa I.,
Nichols David E.,
Barker Eric L.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.714.7
Subject(s) - homology modeling , monoamine neurotransmitter , transporter , serotonin transporter , aquifex aeolicus , chemistry , biochemistry , amino acid transporter , biophysics , serotonin , biology , enzyme , receptor , gene , escherichia coli
Appropriate removal of monoamine neurotransmitters after release into the synapse is mediated by presynaptic transporters. Many neurological disorders have been implicated in the dysfunction of these important drug targets. A high‐resolution crystal structure for the monoamine transporters is yet to be resolved. We have developed a homology model for the serotonin transporter (SERT) based on the crystal structure of the leucine transporter (LeuT Aa ) from Aquifex aeolicus . The objective of my studies is to identify the structural determinants to the entrance into the substrate permeation pathway based on predictions drawn from the homology model. Taking advantage of the substituted cysteine accessibility method (SCAM), we identified residues that were sensitive and accessible to different MTS (methanethiosulfonate) reagents. These residues were protected against MTS reactivity with different SERT ligands. Moreover, those residues with significant changes in MTS reactivity after ligand protection were further analyzed by determining their rate of inactivation. Furthermore, bifunctional MTS cross‐linkers were used to assess the proximity of the helices predicted to be forming the entrance into the protein pore. Our studies provide the opportunity to refine the model and further extend SERT structural characterization. This research supported by NIH grant R01DA018682.