Ribosome

The Small Subunit

The structure of the small subunit is available in the PDB entries 1fka and 1fjg. The small subunit is in charge of information flow during protein synthesis. It initially finds a messenger RNA strand and, after combining with a large subunit, ensures that each codon in the message is paired with the anticodon in the proper transfer RNA. The messenger RNA is thought to enter through a small hole (seen here on the left side of the molecule) and then extend up into the "decoding center" in the cleft between the "head" at top and the "body" at the bottom. The messenger RNA does not have to thread through this hole like a needle, however, because the hole is actually formed by a loop of the ribosomal RNA, which can open like a latch to admit the messenger.

To download an animated movie of this subunit, click on the molecule.