Virus uses 'Swiss Army knife' protein to cause infection

August 17, 2011

In an advance in understanding Mother Nature's copy machines, motors, assembly lines and other biological nano-machines, scientists are describing how a multipurpose protein on the tail of a virus bores into bacteria like a drill bit, clears the shavings out of the hole and enlarges the hole. They report on the "Swiss Army Knife" protein, which enables the virus to pump its genetic material into and thus infect bacteria, in the Journal of the American Chemical Society.

Akio Kitao and colleagues focus on a group of viruses termed "bacteriophages," which literally means "bacteria eaters." These viruses infect bacteria like E. coli and usually make the bacteria dissolve. Infection involves injecting their own DNA or RNA into the bacteria, so that the viral genetic material takes over control of the bacteria. The tools for doing so are among numerous invisible nanomachines -- so small that 50,000 would fit across the width of a human hair --that work unnoticed in organisms ranging from microbes to people.

The scientists recreated intricate details of the protein's work as it helps the tail of the virus infect E. coli bacteria. Their computer models show that the protein performs tasks in a regular sequence, starting with a screw-like motion as it begins to penetrate the outer membrane of E. coli. The protein acts as a cell-puncturing bit, a pipe to draw away membrane debris and a tool to enlarge the puncture hole, among other functions. The infection process demonstrates "a case where a single-function protein acquired multiple chemical functions" as different parts of its structure come in contact with bacterial membrane proteins.
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The authors acknowledge funding from the Ministry of Education, Culture, Sports, Science and Technology-Japan (MEXT) and Japan Science and Technology Agency (JST).

American Chemical Society

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