To initiate translation,
a 30S ribosomal subunitbinds to a short nucleotide sequence on the mRNA called
the ribosome binding site. However, translation doesn't usually begin until
the 30S ribosomal subunit reaches the first AUG sequence in the mRNA. For
this reason, AUG is known as the start codon. At this point, an initiation
complex composed of the 30S subunit, a tRNA having the anticodon UAC and carrying
an altered form of the amino acid methionine (N-formylmethionine or
f-Met), and proteins called initiation factors is formed.
