author_facet Chen, Jie-Guang
Rudnick, Gary
Chen, Jie-Guang
Rudnick, Gary
author Chen, Jie-Guang
Rudnick, Gary
spellingShingle Chen, Jie-Guang
Rudnick, Gary
Proceedings of the National Academy of Sciences
Permeation and gating residues in serotonin transporter
Multidisciplinary
author_sort chen, jie-guang
spelling Chen, Jie-Guang Rudnick, Gary 0027-8424 1091-6490 Proceedings of the National Academy of Sciences Multidisciplinary http://dx.doi.org/10.1073/pnas.97.3.1044 <jats:p>The third transmembrane domain (TM3) of serotonin transporter (SERT) contains two isoleucine residues previously proposed to be involved in binding and transport of serotonin. When Ile-172 was replaced with cysteine, SERT became sensitive to inactivation by externally added [2-(trimethylammonium)ethyl]methanethio-sulfonate (MTSET). The disulfide product of this inactivation was not sensitive to reduction by externally added sulfhydryl compounds, but apparently reacted with intracellular reducing agents to spontaneously regenerate active SERT. The apparent accessibility of this residue to both external and cytoplasmic reagents is consistent with its localization near a serotonin binding site that is alternately exposed to both internal and external media. In another SERT mutant, I179C, transport also was inactivated by MTSET but substrate binding was resistant. External substrate bound to the inactivated I179C and enhanced its reactivation by free thiols. In norepinephrine transporter (NET), cysteine replacement of Ile-155 (corresponding to SERT Ile-179) also rendered the transporter sensitive to MTSET inactivation. In NET I155C, cocaine enhanced this inactivation, and the substrate, dopamine, apparently protected against inactivation. The characteristics of this protection suggest that dopamine was transported, converting NET to a form in which Ile-155 was occluded. The results support the proposal that TM3 of SERT and NET constitute part of the substrate permeation pathway, and that Ile-172 in SERT resides close to the substrate binding site. They also suggest that Ile-179 in SERT (and Ile-155 in NET) is in a conformationally sensitive part of TM3, which may act as part of an external gate.</jats:p> Permeation and gating residues in serotonin transporter Proceedings of the National Academy of Sciences
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title Permeation and gating residues in serotonin transporter
title_unstemmed Permeation and gating residues in serotonin transporter
title_full Permeation and gating residues in serotonin transporter
title_fullStr Permeation and gating residues in serotonin transporter
title_full_unstemmed Permeation and gating residues in serotonin transporter
title_short Permeation and gating residues in serotonin transporter
title_sort permeation and gating residues in serotonin transporter
topic Multidisciplinary
url http://dx.doi.org/10.1073/pnas.97.3.1044
publishDate 2000
physical 1044-1049
description <jats:p>The third transmembrane domain (TM3) of serotonin transporter (SERT) contains two isoleucine residues previously proposed to be involved in binding and transport of serotonin. When Ile-172 was replaced with cysteine, SERT became sensitive to inactivation by externally added [2-(trimethylammonium)ethyl]methanethio-sulfonate (MTSET). The disulfide product of this inactivation was not sensitive to reduction by externally added sulfhydryl compounds, but apparently reacted with intracellular reducing agents to spontaneously regenerate active SERT. The apparent accessibility of this residue to both external and cytoplasmic reagents is consistent with its localization near a serotonin binding site that is alternately exposed to both internal and external media. In another SERT mutant, I179C, transport also was inactivated by MTSET but substrate binding was resistant. External substrate bound to the inactivated I179C and enhanced its reactivation by free thiols. In norepinephrine transporter (NET), cysteine replacement of Ile-155 (corresponding to SERT Ile-179) also rendered the transporter sensitive to MTSET inactivation. In NET I155C, cocaine enhanced this inactivation, and the substrate, dopamine, apparently protected against inactivation. The characteristics of this protection suggest that dopamine was transported, converting NET to a form in which Ile-155 was occluded. The results support the proposal that TM3 of SERT and NET constitute part of the substrate permeation pathway, and that Ile-172 in SERT resides close to the substrate binding site. They also suggest that Ile-179 in SERT (and Ile-155 in NET) is in a conformationally sensitive part of TM3, which may act as part of an external gate.</jats:p>
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author Chen, Jie-Guang, Rudnick, Gary
author_facet Chen, Jie-Guang, Rudnick, Gary, Chen, Jie-Guang, Rudnick, Gary
author_sort chen, jie-guang
container_issue 3
container_start_page 1044
container_title Proceedings of the National Academy of Sciences
container_volume 97
description <jats:p>The third transmembrane domain (TM3) of serotonin transporter (SERT) contains two isoleucine residues previously proposed to be involved in binding and transport of serotonin. When Ile-172 was replaced with cysteine, SERT became sensitive to inactivation by externally added [2-(trimethylammonium)ethyl]methanethio-sulfonate (MTSET). The disulfide product of this inactivation was not sensitive to reduction by externally added sulfhydryl compounds, but apparently reacted with intracellular reducing agents to spontaneously regenerate active SERT. The apparent accessibility of this residue to both external and cytoplasmic reagents is consistent with its localization near a serotonin binding site that is alternately exposed to both internal and external media. In another SERT mutant, I179C, transport also was inactivated by MTSET but substrate binding was resistant. External substrate bound to the inactivated I179C and enhanced its reactivation by free thiols. In norepinephrine transporter (NET), cysteine replacement of Ile-155 (corresponding to SERT Ile-179) also rendered the transporter sensitive to MTSET inactivation. In NET I155C, cocaine enhanced this inactivation, and the substrate, dopamine, apparently protected against inactivation. The characteristics of this protection suggest that dopamine was transported, converting NET to a form in which Ile-155 was occluded. The results support the proposal that TM3 of SERT and NET constitute part of the substrate permeation pathway, and that Ile-172 in SERT resides close to the substrate binding site. They also suggest that Ile-179 in SERT (and Ile-155 in NET) is in a conformationally sensitive part of TM3, which may act as part of an external gate.</jats:p>
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spelling Chen, Jie-Guang Rudnick, Gary 0027-8424 1091-6490 Proceedings of the National Academy of Sciences Multidisciplinary http://dx.doi.org/10.1073/pnas.97.3.1044 <jats:p>The third transmembrane domain (TM3) of serotonin transporter (SERT) contains two isoleucine residues previously proposed to be involved in binding and transport of serotonin. When Ile-172 was replaced with cysteine, SERT became sensitive to inactivation by externally added [2-(trimethylammonium)ethyl]methanethio-sulfonate (MTSET). The disulfide product of this inactivation was not sensitive to reduction by externally added sulfhydryl compounds, but apparently reacted with intracellular reducing agents to spontaneously regenerate active SERT. The apparent accessibility of this residue to both external and cytoplasmic reagents is consistent with its localization near a serotonin binding site that is alternately exposed to both internal and external media. In another SERT mutant, I179C, transport also was inactivated by MTSET but substrate binding was resistant. External substrate bound to the inactivated I179C and enhanced its reactivation by free thiols. In norepinephrine transporter (NET), cysteine replacement of Ile-155 (corresponding to SERT Ile-179) also rendered the transporter sensitive to MTSET inactivation. In NET I155C, cocaine enhanced this inactivation, and the substrate, dopamine, apparently protected against inactivation. The characteristics of this protection suggest that dopamine was transported, converting NET to a form in which Ile-155 was occluded. The results support the proposal that TM3 of SERT and NET constitute part of the substrate permeation pathway, and that Ile-172 in SERT resides close to the substrate binding site. They also suggest that Ile-179 in SERT (and Ile-155 in NET) is in a conformationally sensitive part of TM3, which may act as part of an external gate.</jats:p> Permeation and gating residues in serotonin transporter Proceedings of the National Academy of Sciences
spellingShingle Chen, Jie-Guang, Rudnick, Gary, Proceedings of the National Academy of Sciences, Permeation and gating residues in serotonin transporter, Multidisciplinary
title Permeation and gating residues in serotonin transporter
title_full Permeation and gating residues in serotonin transporter
title_fullStr Permeation and gating residues in serotonin transporter
title_full_unstemmed Permeation and gating residues in serotonin transporter
title_short Permeation and gating residues in serotonin transporter
title_sort permeation and gating residues in serotonin transporter
title_unstemmed Permeation and gating residues in serotonin transporter
topic Multidisciplinary
url http://dx.doi.org/10.1073/pnas.97.3.1044