Eliminating Drug Dealers with Ricin
Ricin (pictured) is a highly toxic lectin that is produced from the seeds of the castor-oil plant (Ricinus communis). Lectins are proteins or glycoproteins with a specific ability to bind sugar. This allows them to selectively react with carbohydrates on cell membranes.
Source: Aza Toth with reference to the “Protein Data Bank (DOI: 10.2210/pdb2aai/pdb) of the Research Collaboratory for Structural Bioinformatics (RCSB)”
Ricin itself is a macromolecule made up of two units connected by disulfide bridges. The effectomer (A chain) has a molecular weight of 32 kDa and is responsible for the toxicity of the molecule. The N-glycosidases of the A chain cause a deadenylation and thus the degradation of the ribosome’s 28S-rRNA, which then blocks protein synthesis in the entire cell . The haptomer (B chain) with a molecular weight of 34 kDa only has the function of binding carbohydrates.
Walter uses ricin for tactical reasons. Although 200–300 µg is enough to kill an adult, death does not occur immediately. It requires 48 to 72 hours. Protein synthesis is blocked during this time meaning that vitally essential proteins cannot be formed. The primary symptoms (nausea, vomiting, general weakness) do not directly indicate poisoning. Ricin is also very difficult to trace in the body. Walter’s motives are not exactly humane – but understandable in the circumstances. Who wants to have a Mexican drug cartel as an enemy after all?
 E. A. E. Garbner, J. Food Prot. 2008, 71, 1875–1883. Link