Gated Access to the Pore of a P2X Receptor STRUCTURAL IMPLICATIONS FOR CLOSED-OPEN TRANSITIONS
Gated Access to the Pore of a P2X Receptor STRUCTURAL IMPLICATIONS FOR CLOSED-OPEN TRANSITIONS
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DOI：
10.1074/jbc.m109.089185
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发表时间：
2010-03-26
影响因子：
4.8
通讯作者：
Khakh, Baljit S.
中科院分区：
文献类型：
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作者：
Kracun, Sebastian;Chaptal, Vincent;Khakh, Baljit S.
P2 X受体是配体门控的阳离子通道，其在结合ATP时从封闭状态转变为开放状态。闭合的斑马鱼P2X4.1受体的晶体结构直接揭示了离子传导途径由三个跨膜结构域2（TM 2）α-螺旋形成，每个螺旋由三聚体的三个亚基提供。然而，TM 2中伴随通道开放的转变还没有完全理解，仍然没有解决。在这项研究中，我们定量门控访问Cd 2+在取代的半胱氨酸在TM 2的P2 X2受体在开放和关闭状态。我们的数据为关闭状态是一致的斑马鱼P2X4.1结构，异亮氨酸和苏氨酸（Ile-332和Thr-336）定位一个螺旋圈分开内衬通道壁的方法到门。我们关于开放状态的数据揭示了通向孔的更深部分（Thr-339、瓦尔-343、Asp-349和Leu-353）的门控通路，这表明关闭的通道门在Thr-336和Thr-339之间。我们还发现了天然Cys-348和D349 C之间的意外相互作用，导致在开放状态下细胞内前庭深处的紧密Cd 2+结合。解释与P2 X2受体结构模型的关闭状态，我们的数据表明，通道门附近的Thr-336/Thr-339开放，并伴随着移动的孔衬区域，缩小到胞质端TM 2在开放状态。这种转变将缓解对离子流的屏障，并使细胞内前庭在ATP存在下的通道开放期间不那么张开。
P2X receptors are ligand-gated cation channels that transition from closed to open states upon binding ATP. The crystal structure of the closed zebrafish P2X4.1 receptor directly reveals that the ion-conducting pathway is formed by three transmembrane domain 2 (TM2) alpha-helices, each being provided by the three subunits of the trimer. However, the transitions in TM2 that accompany channel opening are incompletely understood and remain unresolved. In this study, we quantified gated access to Cd2+ at substituted cysteines in TM2 of P2X2 receptors in the open and closed states. Our data for the closed state are consistent with the zebrafish P2X4.1 structure, with isoleucines and threonines (Ile-332 and Thr-336) positioned one helical turn apart lining the channel wall on approach to the gate. Our data for the open state reveal gated access to deeper parts of the pore (Thr-339, Val-343, Asp-349, and Leu-353), suggesting the closed channel gate is between Thr-336 and Thr-339. We also found unexpected interactions between native Cys-348 and D349C that result in tight Cd2+ binding deep within the intracellular vestibule in the open state. Interpreted with a P2X2 receptor structural model of the closed state, our data suggest that the channel gate opens near Thr-336/Thr-339 and is accompanied by movement of the pore-lining regions, which narrow toward the cytosolic end of TM2 in the open state. Such transitions would relieve the barrier to ion flow and render the intracellular vestibule less splayed during channel opening in the presence of ATP.