Proton and cation transport activity of the M2 proton channel from influenza A virus
Proton and cation transport activity of the M2 proton channel from influenza A virus
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DOI：
10.1073/pnas.1009997107
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发表时间：
2010-08-31
影响因子：
11.1
通讯作者：
Arskold, Sindra Peterson
中科院分区：
文献类型：
--
作者：
Leiding, Thom;Wang, Jun;Arskold, Sindra Peterson
M2蛋白是来自甲型流感病毒的小的单跨膜（TM）蛋白。这种病毒通过内体进入细胞;随着内体成熟并变得更加酸性，M2促进质子转运到病毒内部，从而破坏感染性所需的基质蛋白/RNA相互作用。一个谜团是质子如何在病毒内部积累而不产生阻碍质子进一步向内移位的大电势。解决这一问题的进展一直受到单向插入病毒样囊泡的蛋白质的强大方法的可用性的限制。使用一个优化的程序重建，我们表明，M2具有antiporter样的活性，促进K+或Na+流出时，质子流入囊泡的浓度梯度。阳离子流出非常小，除非在模拟内体截留病毒所遇到的条件下，其中质子流过通道。该质子/阳离子交换功能与通道的已知高质子选择性一致。因此，M2充当质子单向转运体，偶尔允许K+流动以保持电中性。值得注意的是，随着含有M2的囊泡内的pH（pH（in））降低，M2的质子通道活性被抑制，但其阳离子转运活性被激活。随着pH（in）降低，质子通量的这种相互抑制和阳离子通量的激活首先允许质子在酸化的早期阶段积累，然后当达到低pH（in）时，质子被捕获在病毒内。
The M2 protein is a small, single-span transmembrane (TM) protein from the influenza A virus. This virus enters cells via endosomes; as the endosomes mature and become more acidic M2 facilitates proton transport into the viral interior, thereby disrupting matrix protein/RNA interactions required for infectivity. A mystery has been how protons can accumulate in the viral interior without developing a large electrical potential that impedes further inward proton translocation. Progress in addressing this question has been limited by the availability of robust methods of unidirectional insertion of the protein into virus-like vesicles. Using an optimized procedure for reconstitution, we show that M2 has antiporter-like activity, facilitating K+ or Na+ efflux when protons flow down a concentration gradient into the vesicles. Cation efflux is very small except under conditions mimicking those encountered by the endosomally entrapped virus, in which protons are flowing through the channel. This proton/cation exchange function is consistent with the known high proton selectivity of the channel. Thus, M2 acts as a proton uniporter that occasionally allows K+ to flow to maintain electrical neutrality. Remarkably, as the pH inside M2-containing vesicles (pH(in)) decreases, the proton channel activity of M2 is inhibited, but its cation transport activity is activated. This reciprocal inhibition of proton flux and activation of cation flux with decreasing pH(in) first allows accumulation of protons in the early stages of acidification, then trapping of protons within the virus when low pH(in) is achieved.