Permeation and gating residues in serotonin transporter
AUTOR(ES)
Chen, Jie-Guang
FONTE
The National Academy of Sciences
RESUMO
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.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=15515Documentos Relacionados
- Single-channel currents produced by the serotonin transporter and analysis of a mutation affecting ion permeation.
- Voltage gating and permeation in a gap junction hemichannel.
- Oligomerization of serotonin transporter and its functional consequences
- Serotonin Transporter Polymorphisms in Patients With Portopulmonary Hypertension
- Social supports and serotonin transporter gene moderate depression in maltreated children