The Triangle

Issue date: 2/25/05 Section: Sci-Tech
Originally published: 2/24/05 at 10:37 PM EST
Last update: 2/24/05 at 10:49 PM EST

Media Credit: http://www.science-projects.com/ Cholesterol

Rod Tweten, of Ohio State University, gave a seminar in the Living Arts Lounge Feb. 22 on the mechanism of pore formation by cholesterol-dependent cytolysins. The Dept. of Bioscience and Biotechnology and the College of Medicine anthrax team gained insight about anthrolysin O, the anthrax protein, which is currently under study at our university.

The cholesterol-dependent cytolysin Anthrolysin O (ALO), found in Bacillus anthracis, is suggested to be implicated in anthrax virulence. According to the Centers for Disease Control and Prevention, ALO has been categorized as a Category A bioterrorism agent, meaning that it poses the greatest possible threat to public health. Anthrax can seriously affect the skin, lungs, and digestive tract when dormant spores are activated under certain conditions. The impact on public health is appreciated when recognizing that Bacillus anthracis spores are agents of biological terrorism.

Media Credit: http://textbookofbacteriology.net/ Bacillus anthracis, which contains Anthrolysin O (ALO), a Category A bioterrorism agent.

Tweten explained how cytolysins, one of which is implicated in anthrax, bind to the plasma membrane and form large pores. Cholesterol-dependent cytolysins are produced by more than 20 Gram-positive bacteria, including Bacillus, Clostridium, and Streptococcus. The mechanisms of pore formation involves binding, prepore formation, and pore formation. Of these steps, prepore formation was proven to be cholesterol-sensitive, as cell membranes depleted of cholesterol were not targeted by cytolysins.

Although human cells containing CD59 membrane proteins are resistant to certain cytolysins, such as perfringolysin O from Clostridium and streptolysin O from streptococcus, intermedilysins are specific to human cells. These findings are based on hemolysis experiments on erythrocyte-containing blood agar plates.

Amyloid proteins, which are implicated in the deposition of plaques in the brains of Alzheimer's patients, are also implicated in pore formation. As we come to know more about science, we take a step back and realize that we are coming to know less and less, as the boundaries in the field of science are endless.

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