Translation

Translation is the process in which an mRNA template is used to synthesize polypeptides. In translation, the ribosome complex is constructed (small 30S subunit + large 50S subunit, for prokaryote) on the mRNA in conjunction with initiator tRNA. The P ribosome binding site is matched with the start codon (AUG), and the methylated initiating tRNA associates with the region. As elongation begins, elongation factors use GTP to help establish the new tRNA into the A site. Peptide bond formation is assisted by the 23S rRNA as the polypeptide chain grows. As the ribosome moves along the mRNA, translocation is powered from one codon to the next by GTP hydrolysis. The leaving tRNA is released from the E site. Translation continues as new tRNA enters the A site. Protein synthesis ends when a stop codon is reached which is recognized by release factors.

In bacteria, 16S rRNA participates in initiation by base pairing with the ribosome binding site. The 23S rRNA participates in translocation besides just structural support.

In regards to defective mRNA in bacteria, bacteria are known to contain tmRNA that frees stalled ribosomes. The tmRNA collides with the stalled ribosome and binds with the faulty mRNA. tmRNA contains a stop codon and stops translation by recognition by release factors.