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Biochemistry

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Toxic Lectins: Ricin

BIOCHM-C9C9KO

Lectins are a large family of proteins that occur throughout nature. Not all lectins are good; ricin is a deadly lectin isolated from castor oil plants and can be fatal. Less than 2 mg is sufficient to likely kill an adult with death occurring within 36-72 hours.

Ricin has two domains; the first allows the protein to enter a cell and the second has N-glycosidase enzymatic activity. Most lectins do not have enzymatic activity but ricin is one of those that does.

The N-glycosidase enzymatic activity produces which of the following deadly results?

A

Agglutinates RBCs (red blood cells) resulting in blood clots and stroke.

B

Cleaves nucleobases from DNA resulting in base pair mismatches and chromosomal damage.

C

Cleaves nucleobases from ribosomal RNA resulting in inhibition of protein synthesis and cell death.

D

Cleaves galactose from blood group antigens resulting in an autoimmune response that targets the bodies own blood cells.