Bacterial Translation Initiation - Mechanism and Regulation.

Bacterial protein synthesis is a conserved process proceeding through the phases initiation, elongation, termination and recycling. Here we focus on initiation, which is the rate limiting and the most regulated of the different translation phases. The ribosome, at least the three protein factors initiation factor IF1, initiation factor IF2 and initiation factor IF3, the amino acylated initiator tRNA fMet-tRNA Met f and an mRNA are involved in the translation initiation phase. In this process the translation initiation region of mRNA is bound to the 30S ribosomal subunit, then followed by decoding of the initiation codon, which is aided and controlled by the initiation factors IF1, IF2 and IF3 as well as fMet-tRNA Met f. Afterwards, as late translation initiation events, IF1 and IF3 dissociate from the 30S initiation complex, and the 50S ribosomal subunit joins, GTP associated with IF2 is hydrolyzed and IF2 exits the complex. This 70S ribosome initiation complex is now competent to enter the elongation phase.