The 43S is an important intermediate complex during cap-dependent translation initiation. In the canonical model of translation initiation, the 43S PIC is pre-formed as a stable complex and recruited to the 5 cap of eukaryotic messenger RNAs (mRNAs) by the eIF4F complex. The 43S PIC then "scans" in the 5 --> 3' direction along the mRNA in an ATP-dependent fashion (via eIF4A and/or other RNA helicases such as Ded1/DDX3 and DHX29) to locate the start codon. Start codon recognition occurs through base-pairing between the Met-tRNA and AUG in the ribosomal P-site and a number of associated changes, and is followed by joining of the large 60S ribosomal subunit to form the 80S ribosome.