Question

In the first step of initiation complex formation, which factors bind to the small ribosomal subunit to prevent it from associating with the large ribosomal subunit?

Answer 1

Initiation factor IF3 binds to the 30S small ribosomal subunit to prevent its premature association with the 50S large ribosomal subunit during initiation complex formation in prokaryotes.

Step-by-step explanation:

In the process of initiation complex formation, specifically in prokaryotic cells, the small ribosomal subunit (30S in prokaryotes) binds to the initiation factors IF1, IF2, and IF3. One crucial function of these initiation factors is to prevent premature association with the large ribosomal subunit (50S in prokaryotes).

Particularly, IF3 plays a key role by binding to the 30S subunit and blocking its union with the 50S subunit.

This ensures that the small subunit can first properly bind to the mRNA and the initiator tRNA can locate the AUG start codon before the large subunit joins to complete the initiation complex, with the initiator fMet-tRNAfMet positioned in the P site of the ribosome.

This order of events is essential for accurate initiation of protein synthesis.