RCA(60): Purification and characterization of ricin D isoforms from Ricinus sanguineus

Ricin is one of the well known potent plant toxins extracted from Ricinus c ommunis (Rc). It is documented that ricin can exist in the same plant in di fferent isoforms depending on the bean's type and the plant variety from wh ich it is purified. Ricinus sanguineus (Rs) is one variety of Ricinus plant grown in France. It was found that ricin D from Rs has different isoforms (R-11, R-12 and R-2) They were found to have the same molecular masses in r educed and non-reduced conditions. Ricin D isoforms from Rs were found to h ave pi values from 7.0 up to 9.6. Ricin D isoform R-12 was found 100 times more toxic than the isoforms R-11 and R-2. The phospholipase activity of th e three ricin D isoforms was tested on 1,2-diplamitoylsn-glycero-3-phosphor ylcholine. Ricin D isoform R-12 showed a specific activity of 4 nmol/h/mg p rotein compared with 2.5 nmol/h/mg protein for R-11 and R-2. It is hypothes ized that this higher phospholipase activity may be related to the increase d cytotoxicity of ricin R12 isoform and, in part, accounts for the low cyto toxicity of R-11 and R-2.