Structural View of Biology
Health and Disease
Biomolecular structures allow us to understand the molecular nature of healthy cells and treat the underlying molecular causes of disease. Our cells contain thousands of molecules that must all work in concert to keep us healthy. When any of these molecules fails, or when a poison or pathogenic organism attacks these molecules, it may cause disease. Our bodies have many defenses against disease, and medical science has developed powerful drugs to assist these defenses.
Toxins and Poisons
Toxins and poisons bind to critical molecules in cells, blocking their action and killing the cell. Bacterial toxins are often particularly deadly, because they specifically bind to cells, force themselves inside, and destroy many copies of the cellular target.
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Anthrax is a household word, in spite of the fact that anthrax is not a common disease. For humans, anthrax is difficult to contract. It is not transmitted from person to person--it is usually contracted when people come into contact with infected animals or their products. But recently, anthrax has gained the potential to be a major threat through bioterrorism. It is an effective weapon because it forms sturdy spores that may be stored for years, that rapidly lead to lethal infections when inhaled.
Discussed StructuresAnthrax toxin is composed of three proteins. This structure includes the protective antigen, the part that delivers the toxin to cells that will be attacked.Anthrax toxin is composed of three proteins. This structure includes the edema factor, which produces a flood of cyclic AMP inside cells, destroying their normal signaling processes.Anthrax toxin is composed of three proteins. This structure includes the lethal factor, which destroys several signaling molecules inside cells.
Bacteria pull no punches when they fight to protect themselves. Some bacteria build toxins so powerful that a single molecule can kill an entire cell. This is far more effective than chemical poisons like cyanide or arsenic. Chemical poisons attack important molecules one by one, so many, many molecules of cyanide are needed to kill a cell. Bacterial toxins use two strategies to make their toxins far more deadly than this.
Discussed Structurescholera toxinEscherichia coli enterotoxinpertussis toxindiphtheria toxinricin
Ricin is one of the most deadly toxins that has been discovered. A single molecule can kill an entire cell. It's also a very common toxin. It's made by the castor bean plant, which can be found in gardens and wild areas around the world and is widely grown for the oil it produces. The seeds are laced with the toxin: about 8 beans can provide a lethal dose. The structure of ricin reveals how it kills cells, and provides insight into how to create a vaccine to protect against ricin poisoning.
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