Question

How many ATP or ATP equivalents would it take to translate the coding region of an mRNA that encoded 277 many amino acids? (Include the energy used to set up the ribosome, charge the tRNAs using an aminoacyl-tRNA synthetase, choose the correct tRNA, translocate the ribosome, and tear down the ribosome complex at termination. This answer will not include the energy required to synthesize the mRNA in the first place, only the energy to translate 1 polypeptide.

I'm not sure what kind of knowledge you are requesting.

The correct answer for this one is 834. I would like to know how this answer is obtained. Thank you very much.

Answer 1

Answer-

1. During activation of amino acids ATP are required. Attachment of right amino acid with right tRNA requires ATP and this reaction is catalyzed by aminoacyl- tRNA synthetase. So that to charge 277 amino acids with specific tRNA requires 277 ATP's.

2. During initiation of translation initiation factor IF2 bound to GTP involves in pairing of initiator tRNA with initiation codon of mRNA. Then binding of 50S ribosomal subunit with large complex causes hydrolysis of GTP and this marks the release of initiation factors from site. So that in this process 1GTP=1ATP is required.

3. During first step of elongation cycle the incoming aminoacyl- tRNA binds to a complex of GTP- bound EF-Tu. The aminoacyl- tRNA-EF-Tu-GTP complex binds to A site of 70S initiation complex. Then GTP is hydrolyzed and EF-Tu-GDP complex is released from 70S ribosome. So that for each amino acid 1GTP is required. For 277 amino acids 277GTP=277ATP are required.

4. During third step of elongation cycle, translocation , the ribosome moves one codon toward 3' end of mRNA. This movement requires EF-G and the energy provided by the hydrolysis of GTP. After translocation the ribosome is ready for next elongation cycle. So that for 277 amino acids 277GTP will be required by EF-G. The 277 GTP =277ATP.

5. During termination of translation hydrolysis of ester linkage between nascent polypeptide and the tRNA in the P-site and release the completed polypeptide. The hydrolysis of GTP by EF-G leads to dissociation of 50S subunit from 30S tRNA-mRNA complex. In this step 1GTP=1ATP is required.

6. So that totally, 277 ATP for tRNA charging + 1ATP for initiation + 277 ATP for first step of elongation + 277 ATP for third step of elongation + 1ATP for termination = 833ATP.