IF3
IF3 is not universally found in all bacterial species but in E. coli it is required for the 30S subunit to bind to the initiation site in mRNA. In addition, it has several other jobs including stabilization of free 30S subunits, facilitation of 30S subunits binding to mRNA and checking for accuracy against the first aminoacyl-tRNA. It also allows for rapid codon-anticodon pairing for the initiator tRNA to bind quickly to. IF3 is required by the small subunit to form initiation complexes, but has to be released to allow the 50S subunit to bind.
Read more about this topic: Prokaryotic Initiation Factor