Monday, 23 May 2005
323

This presentation is part of: Biological Chemistry Posters

Purification and Characterization of Ricin from Castor seed

Srinivas V.S Chakravartula, New York Medical College, Valhalla, NY and Nagaraj Guttarla, Directorate of Oilseeds Research, Hyderabad, India.

Ricin a toxic protein present in the castor seed belongs to a family of RIP-II (ribosome inactivating proteins)composed of two subunits or two polypeptide units (A&B chain)linked by a single disulfide bond.The A-chain forms the toxic moiety while the B chain binds to the galactose unit of cell receptors and thus termed as lectin(sugar binding protein).Recently there is increasing interest in the medicinal applications of ricin as immunotoxin which have been sucessfully applied in several human diseases.Present avaliable data suggests that ricin exists in several isoforms with a molecular weights ranging between 62,000 to 65,000 daltons and its subunits between 32,000 and 34,000 daltons.Our studies have shown a significant difference in the molecular weights of ricin and its subunits. The molecular weights of ricin and its subunits were 57,257, 29,000 and 28,000 daltons confirmed by SDS-PAGE and Mass spectrometry.Ricin when subjected for amino acid analysis revealed a total of 517 amino acid residues and its subunits composed of 269 and 242 amino acid residues . The total helical content of ricin based on circular dichrosim studies revealed 53.6% which is stabler than other existing isoforms of ricin. Thus our experiments have shown that there could be a variation in ricin structure and also its toxic properties which will be discussed.

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