Toxalbumin

Toxalbumin

Illustration of Ricinus communis, a plant that contains the toxalbumin ricin.

Toxalbumins are a class of plant proteins that are highly toxic. These proteins are ribosome-inactivating proteins (RIPs) that inhibit protein synthesis, leading to cell death. Toxalbumins are found in several plant species, including the well-known castor bean plant (Ricinus communis), which contains the potent toxalbumin ricin.

Structure and Function

Toxalbumins are characterized by their ability to inactivate ribosomes, the cellular machinery responsible for protein synthesis. They achieve this by enzymatically removing an adenine residue from the ribosomal RNA, which is essential for the binding of elongation factors during translation. This action effectively halts protein synthesis, leading to cell death.

Notable Examples

Ricin

Ricin is one of the most well-known toxalbumins, derived from the seeds of the castor bean plant. It is highly toxic to humans and animals, with a lethal dose of just a few milligrams if inhaled or injected. Ricin has been studied for its potential use in bioterrorism and as a chemical warfare agent.

Abrin

Abrin is another potent toxalbumin, found in the seeds of the rosary pea (Abrus precatorius). Like ricin, abrin is highly toxic and can cause severe illness or death if ingested or inhaled.

Mechanism of Action

Toxalbumins exert their toxic effects by targeting the ribosomal RNA within cells. The enzymatic activity of these proteins cleaves a specific adenine base from the 28S rRNA, a component of the 60S subunit of the eukaryotic ribosome. This cleavage prevents the binding of elongation factors, which are necessary for the translocation step of protein synthesis, thereby halting the process and leading to cell death.

Symptoms of Poisoning

Exposure to toxalbumins can cause a range of symptoms depending on the route of exposure. Ingestion can lead to gastrointestinal distress, including nausea, vomiting, and diarrhea, followed by organ failure and death in severe cases. Inhalation can cause respiratory distress, fever, and pulmonary edema.

Treatment

There is no specific antidote for toxalbumin poisoning. Treatment is primarily supportive and symptomatic, focusing on maintaining respiratory and cardiovascular function. In cases of ingestion, activated charcoal may be administered to limit absorption.

Related Pages

• Ricin
• Abrin
• Ribosome-inactivating protein
• Castor oil plant