Ricin: Difference between revisions
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RICIN | RICIN | ||
INTRODUCTION | |||
Ricin is a potent cytotoxin that is synthesized in the edosperm cells | |||
of maturing Riccinus seeds(1). Ricin belongs to a small multi-gene family | |||
(2) that is composed of eight members. It is also important to mention | |||
that Ricin is classified as a Type II heterodimeric Ribosome Inactivating | |||
protein(1). | |||
STRUCTURE | |||
Ricin is a heterodimer that consists of a 32,000 dalton A chain | |||
glycoprotein linked by a disulfide bond to a 32,000 dalton B chain | |||
glycoprotein(2). The A chain enzyme is a globular protein with extensive | |||
secondary structure and a predominate active site(2), where the B chain | |||
is a lectin(2) that binds to galactose-containing surface receptors(3). | |||
FUNCTION | |||
The mechanism employed by Ricin to gain entry to a host cell involves | |||
the heterodimeric properties of the toxin. Firstly the toxin arranges | |||
itself in such a way where its B chain can easily interact with the host | |||
cells receptors and once this happens the B chain can fascilitate the | |||
transfer of the A chain into the Cytoplasm(2). This association between | |||
A and B chain is essential for toxicity(2) without it the Ricin would not be | |||
able to gain access to the cells organelles. Once the A chain gains entry into | |||
the cytosol its target of attack is the ribosome, and its mechanism involves | |||
depurination of a single endenosine residue in 28S ribosome RNA(3); which | |||
inhibits ribosome function, thus stopping protein synthesis. | |||
