Final answer:
When a ribosome binds to the translocon, it moves along the mRNA by one codon with the help of EF-G (translocation), shifts the forming peptide from the A-site to the P-site, and releases the deacylated tRNA into the cytosol.
Step-by-step explanation:
When a ribosome binds to the translocon (Sec61 complex) during the process of translating an mRNA into a protein, three key events occur:
- The ribosome moves along the mRNA towards the 3' end by the distance of one codon (three bases) in a process known as translocation.
- Translocation requires elongation factor-G (EF-G), also known as translocase, which catalyzes GTP hydrolysis to provide the energy for the ribosome's movement.
- As a result of translocation, the newly formed dipeptide is shifted from the A-site to the P-site along with its tRNA, and the deacylated tRNA is released into the cytosol.
This process is essential for the elongation phase of protein synthesis, with the ribosome advancing in three nucleotide steps and catalyzing peptide bond formation between amino acids.