Effect of cytoplasmic tail truncations on the activity of the M2 ion channel of influenza A virus
Effect of cytoplasmic tail truncations on the activity of the M2 ion channel of influenza A virus
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DOI：
10.1128/jvi.73.12.9695-9701.1999
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发表时间：
1999-12-01
影响因子：
5.4
通讯作者：
Lamb, RA
中科院分区：
文献类型：
--
作者：
Tobler, K;Kelly, ML;Lamb, RA
甲型流感病毒的M-2蛋白形成了病毒复制所需的质子通道。M-2离子通道是一个同源四聚体，具有24个残基的N端胞外区、19个残基的跨膜区和54个残基的细胞质尾部。我们在这里表明，N末端的蛋氨酸残基是从成熟蛋白中切割出来的。翻译终止密码子被引入到M-2基因的第46、52、62、72、77、82、87和92位残基。根据改变为终止密码子的氨基酸位置，将缺失突变体命名为Truncx。我们通过测定非洲爪哇卵母细胞中表达的细胞质尾部截断突变体的离子通道活性(对M-2特异性抑制剂金刚烷胺的电流敏感性)来研究细胞质尾部的作用。当随着时间的推移测量它们的电导时，突变体trunc72、trunc77和trunc92的表现与野生型M-2蛋白相似(在30分钟内仅下降4%)。相比之下，干线82的电导下降了28%，干线62的电导下降了27%，干线52的电导下降了81%。在干62和干52的一些细胞中，在30min内可以观察到通道的完全关闭。这些数据表明，M-2离子通道的细胞质尾部区域的作用是在胞外区域暴露于低pH时稳定毛孔以防止过早关闭。
The M-2 protein of influenza A virus forms a proton channel that is required for viral replication. The M-2 ion channel is a homotetramer and has a 24-residue N-terminal extracellular domain, a 19-residue transmembrane domain, and a 54-residue cytoplasmic tail. We show here that the N-terminal methionine residue is cleaved from the mature protein. Translational stop codons were introduced into the M-2 cDNA at residues 46, 52, 62, 72, 77, 82, 87, and 92. The deletion mutants were designated truncx, according to the amino acid position that was changed to a stop codon. We studied the role of the cytoplasmic tail by measuring the ion channel activity (the current sensitive to the M-2-specific inhibitor amantadine) of the cytoplasmic tail truncation mutants expressed in oocytes of Xenopus laevis. When their conductance was measured over time, mutants trunc72, trunc77, and trunc92 behaved comparably to wild-type M-2 protein (a decrease of only 4% over 30 min). In contrast, conductance decreased by 28% for trunc82, 27% for trunc62, and 81%, for trunc52 channels. Complete closure of the channel could be observed in some cells for trunc62 and trunc52 within 30 min. These data suggest that a role of the cytoplasmic tail region of the M-2 ion channel is to stabilize the pore against premature closure while the ectodomain is exposed to low pH.