Ricin is a protein that can be isolated from castor beans. In pure form, ricin is...

Ricin is a protein that can be isolated from castor beans. In pure form, ricin is extremely poisonous when
inhaled or injected. Ricin can bind to eukaryotic ribosomal subunits and cleave them, making them inactive
and ultimately preventing their action.
a. What is the general structure of a ribosome?
b. What biological process is inhibited by ricin if ribosomes are destroyed?
c. Describe the steps of the process named in part b from initiation to termination

Expert Solution

Ribosome is a large and complex molecular machine found in all living cells that serve as the site of biological protein synthesis . Ribosomes link amino acid together in order specified by the mRNA molecule.m

It is made up of dozens of distinct proteins as wells as a few specialised RNA molecule called as rRNA. The ribosomes consists of 2 subunits ----- 1. large 2. small.

Prokaryotes have 70S ribosomes ----------- ( 30S) , 50S. Their small subunit has 16 S RNA, subunit bound to 21 proteins , The large subunit is composed of 5S, 23S, 31 proteins.

Eukaryotes have 80S ( 40S/60S ) . 40S --- 18S RNA / 33 proteins . large subunit --- 5S RNA , 28S RNA 5.8S RNA.

b. Ricin is a toxin that is fatal to humans in extremely small doses is a ribosome inactivating protein ----- damages the ribosomes that carry out protein synthesis . Ricin prevents the cells from assembling various amino acid into proteins according to the messages it receives from mRNA in a process conducted by cells ribosomes.

c. It has an rRNA N glycosylase activity that is responsible for the cleavage of a glycosidic bond within the large rRNA of 60S subunit of eukaryotic ribosome . It specifically and ireversibly hydrolyzes the N glycosidic bond of adenine residue at position A4324. with like 28S rRNA . Te depurination event rapidly and completely inactivates the ribosome resulting in toxicity from inhibited protein synthesis.

gladiator answered 2 years ago

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