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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >SUBUNIT INTERACTIONS IN COORDINATION OF NI2+ IN CYCLIC NUCLEOTIDE-GATED CHANNELS
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SUBUNIT INTERACTIONS IN COORDINATION OF NI2+ IN CYCLIC NUCLEOTIDE-GATED CHANNELS

机译：循环核苷酸门控通道中Ni2 +配位的亚基相互作用

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摘要

Cyclic nucleotide-gated (CNG) channels present a unique model for studying the molecular mechanisms of channel gating, We have studied the mechanism of potentiation of expressed rod CNG channels by Ni2+ as a first step toward understanding the channel gating process. Here we report that coordination of Ni2+ between histidine residues (H420) on adjacent channel subunits occurs when the channels are open, Mutation of H420 to lysine completely eliminated the potentiation by Ni2+ but did not markedly alter the apparent cGMP affinity of the channel, indicating that the introduction of positive charge at the Ni2+-binding site was not sufficient to produce potentiation, Deletion or mutation of most of the other histidines present in the channel did not diminish potentiation by Ni2+, We studied the role of subunit interactions in Ni2+ potentiation by generating heteromultimeric channels using tandem dimers of the rod CNG channel sequence, Injection of single heterodimers in which one subunit contained H420 and the other did not (wt/H420Q or H420Q/wt) resulted in channels that were not potentiated by Ni2+, However, coinjection of both heterodimers into Xenopus oocytes resulted in channels that exhibited potentiation, The H420 residues probably occurred predominantly in nonadjacent subunits when each heterodimer was injected individually, but, when the two heterodimers were coinjected, the H420 residues could occur in adjacent subunits as well, These results suggest that the mechanism of Ni2+ potentiation involves intersubunit coordination of Ni2+ by H420. Based on the preferential binding of Ni2+ to open channels, we suggest that alignment of H420 residues of neighboring subunits into the Ni2+-coordinating position may be associated with channel opening. [References: 35]
机译：环核苷酸门控（CNG）通道为研究通道门控的分子机制提供了独特的模型。我们已研究了Ni2 +增强表达的杆状CNG通道的机制，这是了解通道门控过程的第一步。在这里，我们报告说，当通道打开时，相邻通道亚基上的组氨酸残基（H420）之间发生Ni2 +的配位。将H420突变为赖氨酸可完全消除Ni2 +的增强作用，但并未明显改变通道的表观cGMP亲和力，这表明在Ni2 +结合位点引入正电荷不足以产生增强作用，通道中存在的大多数其他组氨酸的缺失或突变并未减弱Ni2 +的增强作用，我们通过产生亚基相互作用研究了亚基相互作用在Ni2 +增强作用中的作用。使用杆CNG通道序列的串联二聚体形成的异源多聚体通道，注入单个异源二聚体，其中一个亚基包含H420，另一个不包含H420（wt / H420Q或H420Q / wt），导致通道不能被Ni2 +增强，但是，两个异二聚体都进入爪蟾卵母细胞，导致通道显示出增强作用，H420残基可能在分别注射每个异二聚体时，在不相邻的亚基中占优势，但是，当同时注射两个异二聚体时，相邻亚基中也会出现H420残基。这些结果表明，Ni2 +增强的机制涉及H420对Ni2 +的亚基间配位。基于Ni2 +与开放通道的优先结合，我们建议将相邻亚基的H420残基排列成Ni2 +配位的对齐方式可能与通道打开有关。 [参考：35]

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