Energetics and Location of Phosphoinositide Binding in Human Kir2.1 Channels
Energetics and Location of Phosphoinositide Binding in Human Kir2.1 Channels
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DOI：
10.1074/jbc.m113.452540
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发表时间：
2013-06-07
影响因子：
4.8
通讯作者：
Nichols, Colin G.
中科院分区：
文献类型：
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作者：
D'Avanzo, Nazzareno;Lee, Sun-Joo;Nichols, Colin G.
Kir2.1通道是由磷酸肌苷4,5-二磷酸（PI(4,5)P-2）唯一激活的，并且可以被其他磷酸肌苷（PIPs）抑制。使用生化和计算方法，我们评估了PIP通道的相互作用，并区分了那些对结合具有能量关键作用的残基，以及那些通过改变开闭平衡而改变PIP敏感性的残基。有趣的是，每个PIP的结合被不同的突变子集破坏。在硅配体对接表明pip结合到两个位点。第二个次要位点可能对应于通道激活所需的次级阴离子磷脂位点。然而，96-99%的PIP结合定位在第一个簇上，这与最近Kir晶体结构中一般的PI(4,5)P-2结合位置相对应。pip可以包含多个方向；每一个二磷酸化和三磷酸化的物种都具有相当的结合能量，并且比单磷酸化的pip更受青睐。数据表明，PI(4,5)P-2的选择性激活涉及定向特异性，其他pip通过直接竞争抑制这种激活。
Kir2.1 channels are uniquely activated by phosphoinositide 4,5-bisphosphate (PI(4,5)P-2) and can be inhibited by other phosphoinositides (PIPs). Using biochemical and computational approaches, we assess PIP-channel interactions and distinguish residues that are energetically critical for binding from those that alter PIP sensitivity by shifting the open-closed equilibrium. Intriguingly, binding of each PIP is disrupted by a different subset of mutations. In silico ligand docking indicates that PIPs bind to two sites. The second minor site may correspond to the secondary anionic phospholipid site required for channel activation. However, 96-99% of PIP binding localizes to the first cluster, which corresponds to the general PI(4,5)P-2 binding location in recent Kir crystal structures. PIPs can encompass multiple orientations; each di- and triphosphorylated species binds with comparable energies and is favored over monophosphorylated PIPs. The data suggest that selective activation by PI(4,5)P-2 involves orientational specificity and that other PIPs inhibit this activation through direct competition.