Study Reveals How Virus Harpoons Your Cells

摘要： Researchers have deciphered the structure of a harpoon-like protein some viruses use to enter cells and begin infection.美国生物学家的一项研究搞清楚了一种能帮助病毒在人体内传播的蛋白质的结构，这种蛋白质形状如同鱼叉，是多种病毒用来袭击人体健康细胞的“敲门砖”。

Researchers have deciphered the structure of a harpoon-like protein some viruses use to enter cells and begin infection.

The protein is known as fusion (F) protein and is found on the outer surface of parainfluenza virus 5, a so-called "enveloped" virus that fuses its membrane with the membrane of its host cell before infection.

Once the membranes are fused, the virus dumps its genetic content into the healthy human cell's interior, hijacking the cell's replication machinery to clone itself.

Enveloped viruses are responsible for a wide variety of human diseases, including mumps, measles, HIV, SARS and Ebola. The finding could help researchers develop drugs that prevent infection by blocking viral entry into cells.

The researchers crystallized the F protein and used x-ray crystallography to determine its three-dimensional structure.

Doing so revealed a hydrophobic (meaning water-repellent) tip that allows the viral harpoon to latch on more securely to the cell membrane, which is also hydrophobic.

It also provided researchers with more insight into the dramatic structural change that the F protein undergoes while performing its task.

When not in use, the F protein looks like a mushroom, and its hydrophobic tip is folded into a compact form, safely hidden inside the cap.

When the virus comes into contact with a target cell, the cap unfurls and the hydrophobic tip is hurled like a harpoon into the cell's outer membrane.

The F protein then brings the virus and the cell together so their two membranes can merge.

It does this by collapsing back on itself like a metal rod bent so that its ends meet.

"The collapse of the protein acts like a hairpin that snaps together and brings the two membranes together to make them fuse," said Theodore Jardetzky, a structural biologist from Northwestern University and the study's principle investigator.

The research, led by Hsien-Sheng Yin of Northwestern University, is detailed in the Jan. 5 issue of the journal Nature.

美国生物学家的一项研究搞清楚了一种能帮助病毒在人体内传播的蛋白质的结构，这种蛋白质形状如同鱼叉，是多种病毒用来袭击人体健康细胞的“敲门砖”。

据美国“生活科学”网站1月5日报道，这项研究是在美国西北大学生物学家殷献生博士的带领下进行的，详细的研究报告已经刊登在1月5日出版的英国《自然》杂志上。这种在“副流感病毒5型”的外层表面发现的蛋白质通常被叫做“融合蛋白”（fusion protein），即所谓的“包膜”病毒，它可以将自身细胞膜与人体的细胞膜进行融解并感染。一旦细胞膜被融解，病毒就会将自身的基因物质倾注到健康的人体细胞中，并夺取人体细胞能量来进行病毒复制。

研究人员将“融合蛋白”进行结晶处理，然后利用X射线的结晶技术确定它的三维立体结构。生物学家通过显微镜发现，这种蛋白质具有一个防水的顶端。在没有碰到人体细胞时，“副流感病毒5型”细胞表层的“融合蛋白”看起来就像一个蘑菇，防水顶端严密封闭，且安全地藏在蘑菇帽子下面；当病毒接触到人体细胞时，蘑菇帽子会突然破裂开来，防水顶端也像鱼叉一样暴露出来，并陷入人体细胞膜内。“融合蛋白”将病毒和人体细胞连在一起并使细胞膜融解，病毒最后吞噬人体健康的细胞。

报告指出，“包膜”病毒是人类感染许多疾病和病毒的罪魁祸首，其中包括腮腺炎、麻疹、艾滋病病毒、SARS病毒和埃博拉病毒等。据认为，这一发现将有利于科学界进一步研制预防各种病毒感染的药物。

（国际在线独家资讯 程瑶）