Answer to Question #93350 in Molecular Biology for Kylie

Question

Discuss how does the ribosome know where to begin during protein synthesis.

Answer 1

In prokaryotes, the 30S ribosome subunit complex recognizes specific mRNA sequence - ribosome-binding site (RBS). This site contains the start codon AUG and a special Shine-Dalgarno sequence interacting with the ribosomal 16S RNA. The Shine-Dalgarno sequence serves to distinguish the start codon AUG from the internal codons encoding methionine.

In eukaryotes, according to the scanning mechanism, the ribosome binds to the 5'-end of the mRNA at the cap region and moves along the mRNA molecule, scanning one codon after another until it recognizes a start codon AUG.