کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
8998270 | 1115618 | 2005 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Intramolecular cross-linking in a bacterial homolog of mammalian SLC6 neurotransmitter transporters suggests an evolutionary conserved role of transmembrane segments 7 and 8
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کلمات کلیدی
موضوعات مرتبط
علوم زیستی و بیوفناوری
علم عصب شناسی
علوم اعصاب رفتاری
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چکیده انگلیسی
The extracellular concentration of the neurotransmitters dopamine, serotonin, norepinephrine, GABA and glycine is tightly controlled by plasma membrane transporters belonging to the SLC6 gene family. A very large number of putative transport proteins with a remarkable homology to the SLC6 transporters has recently been identified in prokaryotes. Here we have probed structural relationships in a 'microdoman' corresponding to the extracellular ends of transmembrane segments (TM) 7 and 8 in one of these homologs, the tryptophan transporter TnaT from Symbiobacterium thermophilum. We found that simultaneous - but not individual - substitution of Ala286 at the top of TM7 and Met311 at the top of TM8 with cysteines conferred sensitivity to submicromolar concentrations of Hg2+ as assessed in a [3H]tryptophan uptake assay. Because Hg2+ can cross-link pairs of cysteines, this suggests close proximity between TM 7 and 8 in the tertiary structure of TnaT as previously suggested for the mammalian counterparts. Furthermore, the inhibition of uptake upon cross-linking the two cysteines provides indirect support for a conserved conformational role of these transmembrane domains in the transport process. It was not possible, however, to transfer to TnaT binding sites for another metal ion, Zn2+, that we previously engineered in the dopamine (DAT) and GABA (GAT-1) transporters between TM 7 and 8. This suggests that the structure of the TM7/8 microdomain is not identical with that of DAT and GAT-1. Hence, our data also emphasize possible structural differences that should be taken into account when interpreting future data on bacterial homologs of the SLC6 transporters.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Neuropharmacology - Volume 49, Issue 6, November 2005, Pages 715-723
Journal: Neuropharmacology - Volume 49, Issue 6, November 2005, Pages 715-723
نویسندگان
Julie Kniazeff, Claus Juul Loland, Naomi Goldberg, Matthias Quick, Shonit Das, Harald H. Sitte, Jonathan A. Javitch, Ulrik Gether,