Mapping the urea channel through the rabbit Na(+)-glucose cotransporter SGLT1.
Mapping the urea channel through the rabbit Na(+)-glucose cotransporter SGLT1.
复制标题
绘制兔 Na()-葡萄糖协同转运蛋白 SGLT1 的尿素通道图。
DOI：
10.1111/j.1469-7793.2001.00419.x
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Wright,EM
中科院分区：
文献类型：
--
作者：
Panayotova-Heiermann,M;Wright,EM
1兔Na+-葡萄糖协同转运蛋白rbSGLT 1及其羧基末端部分C5（包含SGLT 1的跨膜螺旋10 - 14，作为低亲和力葡萄糖单向转运蛋白）在异种卵母细胞中表达为单个蛋白。通过14 C标记底物的摄取测量，研究了对照卵母细胞和表达SGLT 1和C5的卵母细胞对55 μ m尿素、乙二醇、甘露醇和α-甲基-d-吡喃葡萄糖苷（αMDG）的转运。2与对照卵母细胞相比，C5介导的尿素转运增加了5 - 6倍。与SGLT 1相似，C5-尿素摄取不依赖于阳离子，与时间呈线性关系，且随尿素浓度增加而增加，并被抑制剂根皮素（Ki ≥ 1 mm）以相同的灵敏度阻断。与胆碱缓冲液中的SGLT 1一样，C5介导的摄取对根皮苷不敏感。3甘露糖由C5转运，但不被SGLT 1或对照卵母细胞转运。4尿素通过C5转运的活化能（Ea）较低（5 ± 3 kcal mol−1）与未注射卵母细胞相比（16 ± 0.5 kcal mol−1），与尿素或水通过完整SGLT被动转运的Ea相当1.5存在αMDG时，通过C5的尿素内流增加，但在相同浓度的甘露醇存在下则不然。6我们得出结论，SGLT 1的五个羧基末端跨膜螺旋形成了尿素和水等小分子渗透的通道。
1The rabbit Na+‐glucose cotransporter rbSGLT1 and its carboxy‐terminal part, C5, which contains transmembrane helices 10‐14 of SGLT1 and functions as a low affinity glucose uniporter, were expressed as individual proteins inXenopusoocytes. Transport of 55 μmurea, ethylene glycol, mannitol and α‐methyl‐d‐glucopyranoside (αMDG) by control oocytes and by oocytes expressing SGLT1 and C5 was studied by uptake measurements of the14C‐labelled substrates.2There was a 5‐ to 6‐fold increase in urea transport mediated by C5, compared with control oocytes. Similar to SGLT1, the C5‐urea uptake was cation independent, linear in time and with increasing urea concentration, and blocked with the same sensitivity by the inhibitor phloretin (Ki≈ 1 mm). Like SGLT1 in choline buffer, the C5‐mediated uptake was insensitive to phlorizin.3Mannitol was transported by C5 but not by SGLT1 or control oocytes.4The activation energy (Ea) for urea transport through C5 was low (5 ± 3 kcal mol−1) compared with that of non‐injected oocytes (16 ± 0.5 kcal mol−1) and comparable with theEaof passive urea or water transport through intact SGLT1.5The urea influx through C5 increased in the presence of αMDG, but not in the presence of the same concentration of mannitol.6We conclude that the five carboxy‐terminal transmembrane helices of SGLT1 form a channel for the permeation of small molecules such as urea and water.