Functional Characterization of the Betaine/γ-Aminobutyric Acid Transporter BGT-1 Expressed in Xenopus Oocytes*
Functional Characterization of the Betaine/γ-Aminobutyric Acid Transporter BGT-1 Expressed in Xenopus Oocytes*
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非洲爪蟾卵母细胞中表达的甜菜碱/γ-氨基丁酸转运蛋白 BGT-1 的功能表征*
DOI：
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发表时间：
1999
影响因子：
4.8
通讯作者：
Florian Lang
中科院分区：
文献类型：
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作者：
Ioulia Matskevitch;C. Wagner;C. Stegen;S. Bröer;Birgit Noll;T. Risler;H. Kwon;J. Handler;S. Waldegger;A. Busch;Florian Lang
甜菜碱是一种渗透压物质，在渗透压细胞收缩过程中积累在细胞内。在非洲爪哇卵母细胞中表达了介导渗透调节甜菜碱和神经递质γ-氨基丁酸(BGT-1)积累的犬转运蛋白，并用双电极电压钳和示踪通量研究对其进行了分析。表达BGT-1的卵母细胞在甜菜碱或γ-氨基丁酸的作用下，在电流钳模式下使细胞膜去极化，并在电压钳条件下产生内向电流。在1 mM底物上，诱发电流的顺序为：甜菜碱=γ-氨基丁酸>；二氨基丁酸=β-丙氨酸>；脯氨酸=奎尼丁>；二甲基甘氨酸>；甘氨酸>；肌氨酸。γ-氨基丁酸和甜菜碱诱导电流的Vmax和Km都是电压依赖性的，而γ-氨基丁酸和甜菜碱诱导的电流和放射性示踪剂摄取严格依赖于Na+，但仅部分依赖于Cl-−的存在。随着Na+浓度的降低，GABA的表观亲和力降低。Na+的Km还依赖于γ-氨基丁酸和Cl-−的浓度。Cl-−浓度的降低降低了对Na+和GABA的表观亲和力，Na+浓度的降低降低了对Cl-−和GABA的表观亲和力。比较了~(22)Na~+、~(36)Cl、~(14)C标记的−~-和~(14)C标记的甜菜碱通量以及~(22)Na~+/~(36)Cl-−/有机底物的偶联比为3：1：1或3：2：1。在此基础上，提出了一个有序结合的转运模型，即GABA首先结合，Na~+其次，Cl-−第三。总之，BGT-1与GABA转运蛋白家族的其他成员显示出显著的功能差异。
Betaine is an osmolyte accumulated in cells during osmotic cell shrinkage. The canine transporter mediating cellular accumulation of the osmolyte betaine and the neurotransmitter γ-aminobutyric acid (BGT-1) was expressed inXenopus oocytes and analyzed by two-electrode voltage clamp and tracer flux studies. Exposure of oocytes expressing BGT-1 to betaine or γ-aminobutyric acid (GABA) depolarized the cell membrane in the current clamp mode and induced an inward current under voltage clamp conditions. At 1 mm substrate the induced currents decreased in the following order: betaine = GABA > diaminobutyric acid = β-alanine > proline = quinidine > dimethylglycine > glycine > sarcosine. Both the V max and K m of GABA- and betaine-induced currents were voltage-dependent, and GABA- and betaine-induced currents and radioactive tracer uptake were strictly Na+-dependent but only partially dependent on the presence of Cl−. The apparent affinity of GABA decreased with decreasing Na+ concentrations. TheK m of Na+ also depended on the GABA and Cl− concentration. A decrease of the Cl−concentration reduced the apparent affinity for Na+ and GABA, and a decrease of the Na+ concentration reduced the apparent affinity for Cl− and GABA. A comparison of22Na+-, 36Cl−-, and14C-labeled GABA and 14C-labeled betaine fluxes and GABA- and betaine-induced currents yielded a coupling ratio of Na+/Cl−/organic substrate of 3:1:1 or 3:2:1. Based on the data, a transport model of ordered binding is proposed in which GABA binds first, Na+ second, and Cl−third. In conclusion, BGT-1 displays significant functional differences from the other members of the GABA transporter family.
影响因子：
56.9
作者：
GUASTELLA, J;NELSON, N;KANNER, BI
通讯作者：
KANNER, BI
神经递质转运蛋白的渗透特性。
DOI：
10.1146/annurev.pa.34.040194.001251
发表时间：
1994
影响因子：
12.5
作者：
Lester,HA;Mager,S;Quick,MW;Corey,JL
通讯作者：
Corey,JL
影响因子：
--
作者：
HANDLER, JS;KWON, HM
通讯作者：
KWON, HM