Early Steps in Translation During Bacterial Protein Synthesis:animationانیمیشن متن انگلیسی را با کلیک روی تیتر ببینید

This animation illustrates the early steps of translation during bacterial protein synthesis.
1. To initiate translation, a 30S ribosomal subunit first binds to a sequence on the mRNA called the ribosome binding site found just prior to the start codon AUG.
2. Then a tRNA having a complementary anticodon (UAC) and carrying the amino acid f-methionine (fMet) forms H-bonds with the AUG start codon. This forms the initiation complex for translation.
3. Next, a 50S ribosomal subunit joins the complex. The first tRNA now occupies the P (peptide) site of the 50S subunit.
4. A tRNA that recognizes the next codon along the mRNA (the tRNA anticodon GCG forms H-bonds with the codon CGC) then fills the unoccupied A (acceptor) site of the 50S subunit.
5. A peptide bond forms between the fMet and the newest amino acid, in this case argenine (Arg), carried by the tRNA on the A site. Once the fMet leaves the tRNA on the P site, that tRNA can now leave the ribosome, pick up a new Met, and be recycled.
6. The ribosome now advances a distance of one codon down the mRNA through a process called translocation. During this process, the tRNA with the growing amino acid chain moves to the P site of the 50S subunit.
7. Now, a tRNA with an anticodon complementary to the new codon can come in and occupy the empty A site. A peptide bond forms between the two amino acids on the tRNA at the P site and the newest amino acid attached to the tRNA at the A site.
8. The tRNA leaves the P site to be recycled and the ribosome is translocated to read the next codon along the mRNA.
9. This process continues until the ribosome comes to one of the three stop codons. Since there are no tRNAs having anticodons that are complementary to the stop codons, the protein is released from the ribosome and the 30S and 50S ribosomal subunits separate.