( Scientists at Harvard Medical School (H...)Critical step traced in anthrax infection

Scientists at Harvard Medical School (HMS) have revealed details of a key step in the entry of anthrax toxin into human cells. The work, which grew out of an ongoing effort to produce a better anthrax therapeutic, shows that the protective antigen component of the bacterial toxin plays an active role in transferring the other two components of the toxin through the cell membrane.

The research, led by R. John Collier, professor of microbiology and molecular genetics at HMS, provides insight into the broader question of how proteins cross cell membranes. The findings appear in the July 29 issue of Science.

An anthrax bacterium secretes three nontoxic proteins that assemble into a toxic complex on the surface of the host cell to set off a chain of events leading to cell toxicity and death. Protective antigen (PA) is one of these proteins, and after binding to the cell, seven copies of it assemble into a specific complex that is capable of forming a pore in a cellular membrane. The pore permits the other two proteins, lethal factor (LF) and edema factor (EF), to enter the cell interior, where the factors interfere with metabolic processes, leading to death of the infected individual.

Details surrounding this process are continuing to be uncovered in Collier's lab. "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 LF and EF molecules through," he said. The findings show that it is the latter?the pore takes an active role in protein translocation.

The scientists demonstrated this role by investigating the channel's chemical make-up. Using a procedure known as cysteine-scanning mutagenesis, they identified the hydrophobic, or "greasy," amino acid phenylalanine in protective antigen's pore-forming domain. Seven of these amino acids project into the lumen of the pore and form a collection of greasy residues, nicknamed "the phi-clamp" by the sc
'"/>

Source:Harvard Medical School

Page: 1 2
Related biology news :

1. Critical role in programmed cell death identified
2. White Blood Cell Waste Disposal System Plays Critical Regulatory Role
3. Critical hearing gene helps send auditory messages to brain
4. Scientists seek answers on what activates deadly anthrax spores
5. Antibodies from plants protect against anthrax
6. Defensins neutralize anthrax toxin
7. US Army plans to bulk-buy anthrax
8. New antibody shows promise as cure for anthrax
9. Effective, safe anthrax vaccine can be grown in tobacco plants
10. UCSD study finds anthrax toxins also harmful to fruit flies
11. Driver of anthrax toxicity could lead to late-stage therapy