In bacterial translation, what does the presence of IF-3 prevent?

In bacterial translation, the presence of initiation factor 3 (IF-3) plays a crucial role in the process of protein synthesis by ensuring the correct assembly of the ribosomal subunits. IF-3 prevents the premature association of the large (50S) and small (30S) ribosomal subunits before the initiation of translation can occur.

This action is vital because it allows the small ribosomal subunit to first bind to the mRNA and the initiator tRNA, which together form the initiation complex. By preventing the association of the ribosomal subunits, IF-3 ensures that the ribosome assembles in an orderly manner, allowing for the correct positioning of the mRNA and the initiator tRNA, which is necessary for the accurate recognition of the start codon and the subsequent steps in translation.

Therefore, the function of IF-3 is critical in regulating the initiation phase of translation, ensuring that the ribosome only engages in protein synthesis after all necessary components are correctly aligned and in place.