ID #1811

How does a ribosome distinguish the initiator codon from an internal methionine codon in bacteria? I know it uses the Shine Delgarno sequence but how does it actually use that sequence? Is the sequence always the same and is it approximately 10 nucleotides away from the AUG initiator?

The Shine-Delgarno sequence is a conserved region meaning that the 16s rRNA in the 30S subunit, this sets up the ribosome in the right place to initiate translation. The AUG (initiator codon) is found about 10 bases away and then translation proceeds. The purpose of the Shine-Delgarno sequence is just to get the ribosomal subunit in the right place for making the proteins you want.

 Eukaryotes do things a different way, the small ribosomal subunit the 40s RNA binds to the 5' cap and finds the nearest AUG.

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