Ricin

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                                                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.

Please do NOT make changes to this Sandbox until after April 23, 2010. Sandboxes 151-200 are reserved until then for use by the Chemistry 307 class at UNBC taught by Prof. Andrea Gorrell.

Proteopedia Page Contributors and Editors (what is this?)

Ann Taylor, Douglas Read, Wayne Decatur, Andrea Gorrell, Michal Harel, Joel L. Sussman, Angel Herraez, Alexander Berchansky, Jaime Prilusky, David Canner