Prokaryotic small ribosomal subunit

[3] A portion of the 30S subunit (the 16S rRNA) guides the initiating start codon (5′)-AUG-(3′) of mRNA into position by recognizing the Shine-Dalgarno sequence, a complementary binding site about 8 base pairs upstream from the start codon.

The tightness of the bonding between the Shine-Dalgarno sequence on the mRNA and the 16S rRNA determines how efficiently translation proceeds.

[4] Once the 16S rRNA recognizes the mRNA start codon, a special transfer RNA, f-Met-tRNA, binds and protein translation begins.

[5] The binding site of the f-Met-tRNA on the 30S ribosomal subunit is called the "D-site"[6] This step is required in order for protein synthesis to occur.

[7] The binding of the large subunit causes a conformational change in the 70S, which opens another site for protein translation.

[11] These antibiotics specifically target the prokaryotic ribosomes, hence their usefulness in treating bacterial infections in eukaryotes.

Atomic structure of the 30S Subunit from Thermus thermophilus . Proteins are shown in blue and the single RNA strand in orange. [ 1 ]