Computational Biophysics Group, Research School of Biology, Australian National University , Canberra, ACT 0200, Australia.
Biochemistry. 2013 Feb 5;52(5):967-74. doi: 10.1021/bi301498x. Epub 2013 Jan 23.
Dysfunction of Kir2.1, thought to be the major component of inward currents, I(K1), in the heart, has been linked to various channelopathies, such as short Q-T syndrome. Unfortunately, currently no known blockers of Kir2.x channels exist. In contrast, Kir1.1b, predominantly expressed in the kidney, is potently blocked by an oxidation-resistant mutant of the honey bee toxin tertiapin (tertiapin-Q). Using various computational tools, we show that both channels are closed by a hydrophobic gating mechanism and inward rectification occurs in the absence of divalent cations and polyamines. We then demonstrate that tertiapin-Q binds to the external vestibule of Kir1.1b and Kir2.1 with K(d) values of 11.6 nM and 131 μM, respectively. We find that a single mutation of tertiapin-Q increases the binding affinity for Kir2.1 by 5 orders of magnitude (K(d) = 0.7 nM). This potent blocker of Kir2.1 may serve as a structural template from which potent compounds for the treatment of various diseases mediated by this channel subfamily, such as cardiac arrhythmia, can be developed.
Kir2.1 的功能障碍被认为是心脏内向电流 I(K1) 的主要组成部分，与各种通道病有关，如短 QT 综合征。不幸的是，目前还没有已知的 Kir2.x 通道阻断剂。相比之下，主要在肾脏中表达的 Kir1.1b 被蜜蜂毒素 tertiapin（tertiapin-Q）的氧化抗性突变体强烈阻断。使用各种计算工具，我们表明这两种通道都通过疏水性门控机制关闭，并且在没有二价阳离子和多胺的情况下发生内向整流。然后，我们证明 tertiapin-Q 与 Kir1.1b 和 Kir2.1 的外部前庭结合，其 K(d) 值分别为 11.6 nM 和 131 μM。我们发现，tertiapin-Q 的单个突变将其与 Kir2.1 的结合亲和力提高了 5 个数量级（K(d) = 0.7 nM）。这种 Kir2.1 的有效阻断剂可能成为治疗由该通道亚家族介导的各种疾病的有效化合物的结构模板，例如心律失常。
