Timothy mutation disrupts the link between activation and inactivation in Ca(V)1.2 protein.
Timothy mutation disrupts the link between activation and inactivation in Ca(V)1.2 protein.
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DOI：
10.1074/jbc.m111.255273
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发表时间：
2011-09-09
期刊：
影响因子：
--
通讯作者：
Hering S
中科院分区：
文献类型：
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作者：
Depil K;Beyl S;Stary-Weinzinger A;Hohaus A;Timin E;Hering S
Timothy综合征突变G402 S和G406 R消除了CaV1.2的失活，并导致多器官功能障碍和致命的心律失常。为了深入了解G402 S突变对通道结构和功能的影响，我们系统地突变了兔通道的相应Gly-432并应用同源建模。Gly-432的所有突变（G432 A/M/N/V/W）都减少了通道失活。同源性建模显示Gly-432在所有四个结构域（Gly-432（IS 6）、Ala-780（IIS 6）、Gly-1193（IIIS 6）、Ala-1503（IVS 6））的同源位置形成高度保守的小残基结构基序（G/A/G/A）的一部分。相反，结构域II，III和IV中的相应突变诱导激活和失活曲线的平行移动，表明两个过程之间的保留耦合。激活和失活偶联之间的中断是特异性的Gly-432在结构域I的突变。Gly-432的突变去除了失活，而不管激活的变化。在所有四个结构域中，残基G/A/G/A与来自相邻S6螺旋的较大体积氨基酸紧密接触。这些相互作用显然提供了粘附点，从而将CaV1.2的激活门紧密地密封在关闭状态。这种结构假说得到了G/A/G/A残基突变诱导的激活门控变化的支持。CaV1.2激活和失活门控的结构影响进行了讨论。
The Timothy syndrome mutations G402S and G406R abolish inactivation of CaV1.2 and cause multiorgan dysfunction and lethal arrhythmias. To gain insights into the consequences of the G402S mutation on structure and function of the channel, we systematically mutated the corresponding Gly-432 of the rabbit channel and applied homology modeling. All mutations of Gly-432 (G432A/M/N/V/W) diminished channel inactivation. Homology modeling revealed that Gly-432 forms part of a highly conserved structure motif (G/A/G/A) of small residues in homologous positions of all four domains (Gly-432 (IS6), Ala-780 (IIS6), Gly-1193 (IIIS6), Ala-1503 (IVS6)). Corresponding mutations in domains II, III, and IV induced, in contrast, parallel shifts of activation and inactivation curves indicating a preserved coupling between both processes. Disruption between coupling of activation and inactivation was specific for mutations of Gly-432 in domain I. Mutations of Gly-432 removed inactivation irrespective of the changes in activation. In all four domains residues G/A/G/A are in close contact with larger bulky amino acids from neighboring S6 helices. These interactions apparently provide adhesion points, thereby tightly sealing the activation gate of CaV1.2 in the closed state. Such a structural hypothesis is supported by changes in activation gating induced by mutations of the G/A/G/A residues. The structural implications for CaV1.2 activation and inactivation gating are discussed.