Toxalbumin / Lectin
Definition
Two-chain plant protein (A-chain catalytic, B-chain lectin) that depurinates a specific adenine in 28S rRNA, inactivating the 60S ribosomal subunit. Abrin and ricin are the medico-legally important examples.
- Type
- Two-chain plant protein toxin
- A-chain function
- Catalytic, depurinates a specific adenine in 28S rRNA
- B-chain function
- Lectin, binds the target cell surface
- Key examples
- Ricin (Ricinus communis), abrin (Abrus precatorius)
- Effect
- Inactivates the 60S ribosomal subunit, halting protein synthesis
Common questions
How does a toxalbumin actually kill a cell?+
The A-chain removes a single adenine from ribosomal RNA, permanently disabling the ribosome so the cell can no longer make protein. Death of the cell, and eventually the organism, follows over hours to days rather than immediately.
How is ricin or abrin poisoning confirmed in the laboratory?+
Because the intact protein degrades quickly in the body, labs usually detect a stable marker instead, such as ricinine for ricin, using immunoassay or mass spectrometry on blood or urine rather than looking for the toxin itself.
Is abrin more dangerous than ricin?+
Abrin is generally considered more toxic per gram in animal studies, though both are lethal at microgram quantities and both are treated as medico-legally significant plant poisons in casework.
Related terms
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- Diterpene Alkaloid
- Aconitine and mesaconitine in Aconitum. Bind site 2 of the voltage-gated sodium channel and prevent inactivation. Refractory ventricular arrhythmia, death within hours.
- Keller-Kiliani Test
- Cardiac-glycoside test. Glacial acetic acid + FeCl3 layered with H2SO4 gives a reddish-brown ring and blue-green upper layer for 2-deoxysugars.
- Tropane Alkaloid
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- Vitali-Morin Test
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