Ricin toxin A chain (RTA)

Ricin toxin A chain is the protein subunit of ricin, a highly potent plant-derived toxin from Ricinus communis (castor bean plant)[3][5]. As part of a heterodimeric holotoxin (linked to the B chain via disulfide bond), the A chain is an N-glycoside hydrolase enzyme (approx. 32 kDa, 267 amino acids) that specifically depurinates adenine-4324 in the sarcin-ricin loop of eukaryotic 28S rRNA. This enzymatic lesion irreversibly blocks ribosomal function, thereby halting protein synthesis and rapidly killing affected cells[1][3][5][6]. Ricin toxin A chain is thus both a classic and highly effective ribosome-inactivating protein, responsible for the extreme toxicity of ricin holotoxin. There is significant interest in RTA as a biological warfare/terror agent, as well as a model for developing specific inhibitors and antidotes due to its unique mechanism of action[1][3][5][6].

Other names

Ricin A chainRicin A subunitRTARicin toxin A subunit

Inhibition of the N-glycosidase activity (hydrolysis of adenine in 28S rRNA)[2][4][6]. Small molecule inhibitors bind to the active site, impeding access to substrate rRNA[4][6]. Antibodies neutralize and block uptake or enzymatic activity.