Influenza A virus AM2 protein is an integral membrane protein that is an ion channel (also known as a viroporin). The channel has 24 extracellular residues, 19 residues that span the membrane once and acts as both the channel pore and also the membrane anchoring domain, and a 54-residue cytoplasmic tail. The M2 protein has four identical chains linked via two disulfide bonds that form a four-helix bundle that is 10⁷–10⁸ more permeable to protons than Na⁺ ions. The M2 channel is activated by low pH, His residue 37 is the pH sensor, and Trp residue 41 is the channel gate. The channel is blocked by the antiviral drug amantadine hydrochloride. The influenza B virus BM2 protein does not have homology with the AM2 channel, but BM2 does have the His proton sensor, Trp gate, and is activated by low pH. It is thought that the AM2 and BM2 proteins have common functions in the influenza A and B virus life cycles. Both BM2 and AM2 also facilitate virus budding. The amphipathic helix in the AM2 cytoplasmic tail has an important role in the assembly of the virus, and functional AM2 protein makes the virus independent of the “endosomal sorting complex required for transport” (ESCRT) complex scission.

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甲型和乙型流感病毒离子通道的结构，功能和病理生物学

甲型流感病毒AM2蛋白是必不可少的膜蛋白，它是一个离子通道（也称为viroporin）。该通道具有24个细胞外残基，其中19个残基一次跨过膜并既充当通道孔又充当膜锚定域，并具有5​​4个残基的细胞质尾巴。M2蛋白具有通过两个二硫键连接的四个相同链，这些链形成了一个四螺旋束，该四螺旋束比Na ⁺对质子的渗透性高10 ⁷ –10 ⁸离子。M2通道被低pH值激活，His残留物37是pH传感器，Trp残留物41是通道门。该通道被抗病毒药物盐酸金刚烷胺封闭。乙型流感病毒BM2蛋白与AM2通道不具有同源性，但BM2确实具有His质子传感器Trp门，并被低pH值激活。认为AM2和BM2蛋白在甲型和乙型流感病毒的生命周期中具有共同的功能。BM2和AM2都可以促进病毒出芽。AM2细胞质尾巴中的两亲性螺旋在病毒的组装中具有重要作用，而功能性AM2蛋白使病毒独立于“运输所需的内体分拣复合物”（ESCRT）复杂的决定。