Answer:
There are important differences in the process of mRNA translation between prokaryotes and Eukaryotes.
Step-by-step explanation:
Initiation:
Prokaryotes:
- The 30S subunit of the ribosome binds initiation factors 1 and 3 (IF1 and IF3)
- The shine dalgarno site (where binding of the ribosome occurs) at 5' end of the mRNA, is upstream of the start codon AUG, that leads into the open reading frame
- Initiation occurs at AUG, sometimes GUG but rarely at UUG
- Initiation tRNA carries a N-formyl-methionyl group
- 50S subunit binds, GTP is hydrolyzed to form GDP and the initiation factors are released
Eukaryotes:
- There are 12 initiation factors
- Elongation factors 1A and 3 (ELF-1A and ELF-3) act in a similar manner to IF-1 and IF-3
- There is no shine dalgarno site, instead the ribosome binds to the 5' end of the mRNA and glides down it to the first start codon (AUG); here initiation occurs
- Initiation only occurs at AUG
- The initiation tRNA is the normal methionine tRNA
Elongation:
Prokaryotes:
- Charged tRNA binds to the EF-Tu and the tRNA-EF-Tu complex then binds to the A site on the ribosome
- GTP is hydrolyzed to form GPD and EF-Tu is released
- A peptide bond is created using peptidyl transferase activity in the 23S subunit of rRNA
- EF-G-GTP complex binds to the tRNA-peptide complex found at the A site
- GTP is hydrolyzed and the tRNA peptide moves from the A-site to the P-site
Eukaryotes:
- The elongation factors are different to those found in prokaryotic tranlsation, however the process is the same
Termination:
Prokaryotes:
- Slow process comparable to elongation and begins as soon as the open reading frame is reached, indicated by stop codons UAA, UAG or UGA
- Requires release factors (RFs) which are proteins, not tRNAs
- RF1-3 initiates termination
- RF1 recognizes stop codons UAA/UAG
- RF2 recognizes stop codon UGA
- RF3 is a GTPase, which aids in the removal of RF1 and RF2 post-termination
Eukaryotes:
- Utilize eRF instead of RF1, RF2 and EF2-GTP instead of EF-G