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Report Reveals New Clues to Deadly Anthrax

Bacterial proteins gang up to force entry into cells

THURSDAY, July 28, 2005 (HealthDay News) -- The activity of a pore on the surface of human cells may be a critical step to anthrax infection, according to Harvard Medical School researchers. They believe the finding could help lead to new methods of fighting the deadly bacterium.

Their study, published in the July 29 issue of Science, found that the anthrax bacterium secretes three nontoxic proteins that form into a "toxic complex" on the surface of the host human cell. This sets off a sequence of events that results in cell toxicity and death.

One of the proteins involved in this process is called protective antigen (PA). After it binds to the cell, seven copies of PA assemble into a compound that's able to form a pore in the cellular membrane of the host human cell. This pore enables the two other proteins secreted by the anthrax bacterium -- lethal factor and edema factor -- to enter the human host cell. These proteins interfere with the normal metabolic processes of the human cell, resulting in cell death.

"Until now, we have not known whether the PA pore serves simply as a passive conduit, or alternatively, plays an active role in shepherding the unfolded lethal factor and edema factor molecules through," research leader R. John Collier, professor of microbiology and molecular genetics, said in a prepared statement.

According to the researchers, this study shows that the PA protein does play an active role in enabling these two proteins to invade human cells. The findings could help in the development of improved ways to combat anthrax.

More information

The U.S. Centers for Disease Control and Prevention has more about anthrax.

SOURCE: Harvard Medical School, news release, July 28, 2005
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