Study Reveals How Virus Harpoons Your Cells

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Study Reveals How Virus Harpoons Your Cells

Ker Than

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-repellant) 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.

A three-dimensional model of the HIV virus. Image Courtesy 3DScience.com

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.

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