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Name: Eleanor
Status: student
Grade: 9-12
Location: VA
Country: USA
Date: Winter 2012-2913


Question:
What happens to tRNA after translation? My textbook says it just floats off and I believe my teacher said that tRNA is reused again in the process but how does this happen?



Replies:
As far as I can remember, once tRNA exits from the 40s ribosome at what is called the E site it becomes uncharged after it passes off its amino acid to the growing peptide chain. The tRNA then gets recycled and free for more rounds of recycling. In the very complex process, it is possible one or more elements in the tRNA can be corrupted (mutated?). We think these "errors" may be responsible for some degree of biological changes. So, looks like your teacher had the right answer. Many of the biological reactions occur by Brownian motion resulting in random collisions between the molecules. When 2 molecules are "compatible" they join. What makes them compatible or attractable, I do not know. It may be thought of like 2 people in a very large mall with a lot of people randomly walking around and in and out of stores. One person is looking for a person wearing his or her high school colored sweater. The person keep looking until he or she finds someone wearing exactly that sweater. Then they get together, talk and maybe have some ice cream at the mall's Friendly restaurant.

Stephen R. Dunn Ass't Professor of Medicine (ret.) Kimmel Cancer Center & Division of Nephrology


Hi Eleanor,

Thanks for the question. tRNA is used in making proteins by acting as a ferry to bring in the proper amino acid. tRNA is indeed reused as it is energetically unfavorable for a cell to regenerate a new tRNA molecule for each amino acid used--if that was the case, the cell would starve itself. The tRNA is reused by reattaching an amino acid to the carboxy terminus.

I hope this helps. Please let me know if you have more questions. Thanks Jeff



Eleanor,

Your teacher is indeed correct. After a tRNA binds to a ribosome and its attached amino acid is successfully transfered to the growing polypeptide chain, the resultant free tRNA molecule detaches from the ribosome and goes back into the cytosol. In the cytoplasm, it can pick up another amino acid (of the correct type) through the actions of a protein called an aminoacyl tRNA synthetase. This protein uses an ATP to attach the amino acid to the free tRNA molecule, and it can then be reused for translation at the ribosome.

S. Unterman Ph.D.



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