kuka
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i can't figure out how many ATP and GTP are used in translation process. Please correct me of i'm wrong.
1 ATP to activate amino acid, 2 ATP to attach amino acid to tRNA this 2 ATPs will be used later for peptide bond formation (peptidyl transferase)
Charged tRNA (not initiator tRNA) enters A site, 1 ATP is used.
Large ribosomal subunit binds small, 1 GTP is used.
Above mentioned 2ATPs for peptide bond formation (i'm trying to give it chronologic order)
Ribosome slides downstream 3 nucleotides a message, using 1 GTP
Stop codon enters A site, peptidiltransferase releases chain. 1GTP
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| pringo
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Hi to you dear friend & also to every body,
2 high energy bonds (from one ATP ---> AMP+PPi) will be used in AA. activation which we have them in the binding site between AA & tRNA (3' end), so there is no separate energy other than the one used in activation, for binding; & also Met. activation uses this ATP as well.
For binding of charged tRNA to A site: 1 GTP ---> GDP+P (not ATP)
Peptidyl transferase uses the activation energy (ATP) of AA in P site, to transfer it to A site & make a peptide bond.
& as you said, translocation & peptide release each uses 1 GTP.
When 40s initiation complex forms, 1 GTP will be used & transformed to GDP+Pi, then when 60s binds to 40s this GDP+P will be released.
So each cycle of elongation uses 1 GTP (incoming tRNA) + 1 ATP (pept. transf.) + 1 GTP (translocation), which are 4 high energy bonds.
I'm looking for this in the books. If I found something, I'll post it.
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| freshdoc
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Thanks guys good explanation
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| pringo
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OK, here are more details:
- AA. activation is not a part of initiation phase. ATP---> AMP + PP & the complex of (AMP + AA. + enzyme) is called activated AA. Then the enzyme will bind AA to tRNA with a high energy ester linkage & AMP+E. will be released & reutilized.
- Initiation has some steps. First 40s & 60s are separated & eIFs (3 & 1A) bind to 40s to delay its reassociation with 60s.
- (GTP-eIF2 + Met-tRNA) bind with 40s & form 43s preinitiation complex.
- mRNA will be activated which needs 1 ATP (ATP---> ADP + P).
- 43s preinitiation binds with mRNA & they form 48s initiation complex, & 1 ATP is used again (ATP---> ADP + P).
- 48s init. finds the start codon (AUG).
- GTP bound to eIF2 will be hydrolized---> GDP-eIF2 + P. This reaction causes the release of eIF3 & eIF1A from 48s init. complex ---> rapid association of 60s with 40s & thus forming 80s initiation complex.
So for initiation phase we have 2 ATP + 1 GTP
For elongation: 2 GTP (coz AA is already activated, no further energy is required for peptide bond formation).
For termination: 1 GTP
Overall in each translation cycle: 2 ATP + 4 GTP & 1 ATP in AA activation.
( I think that we should not include the ATP for AA activation in the cycle)
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| kuka
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uh oh i'm glad i posted this question...  great job pringo, now i won't forget. thank you my friend
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| pringo
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You're welcome dear friend, I'll be happy to help you all. bye.
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