Translation Initiation in Prokaryotes: 30S initiation complex

IF-3: 22 kDa. Binds to the 30S subunit and prevents association with the 50S subunit. IF-1: 9 kDa. Binds near the A site therefore directs fmet-tRNA to the P site. IF-2: 120 kDa. Reacts with fmet-tRNA and GTP to form a ternary complex IF-2-GTP-fmet-tRNA. Delivers the ternary complex and mRNA to the partial P site in the 30S subunit-mRNA complex. Triggers GTP hydrolysis when the 50S subunit joins the complex. It does not recognize met-tRNA or any aa tRNA used for elongation.