To initiate translation, a 30S ribosomal subunit first binds to a sequence on the mRNA called the ribosome binding site found just prior to the start codon AUG. Then a tRNA having a complementary anticodon (UAC) and carrying the amino acid f-methionine (fMet) forms H-bonds with the AUG start codon. This forms the initiation complex for translation. Next, a 50S ribosomal subunit joins the complex.

Antibiotics known as aminoglycosides (streptomycin, neomycin, netilmicin, tobramycin, gentamicin, amikacin, etc.) bind to the 30S subunit of bacterial ribosomes and block the attachment of the 50S subunit to the initiation complex.