IF-3 binds to the 30S ribosomal subunit and shifts the equilibrum between 70S ribosomes and their 50S and 30S subunits in favor of the free subunits, thus enhancing the availability of 30S subunits on which protein synthesis initiation begins. Monomer. The 66 residues C-terminal tail is not present in other species. Belongs to the IF-3 family.