The Shine-Dalgarno sequence is a specific, purine-rich arrangement of nucleotides in prokaryotic mRNA that targets the RNA to a small ribosomal subunit for translation. This sequence is required for ribosomal binding and protein synthesis to occur in prokaryotic cells. It is also known as the ribosome binding site.
The Shine-Dalgarno sequence is located upstream from where mRNA translation into proteins takes place, in the 5' untranslated region, or 5' UTR. There are multiple arrangements of nucleotides that can target prokaryotic mRNA to ribosomes for translation to occur, and multiple Shine-Dalgarno sequences have been described by scientists. Typically, the sequence is seen approximately eight to 10 codons upstream of the AUG start codon that signals the beginning of prokaryotic mRNA translation. Despite there being multiple Shine-Dalgarno sequences, they all share a consensus sequence of six nucleotides in a specific order: AGGAGG.
The introduction of mutations to the Shine-Dalgarno sequence can have different effects depending on the type of mutation and its location. A mutation to the sequence may increase the rate of translation, decrease the rate, or have no impact.
The Shine-Dalgarno sequence was first described by Australian scientists John Shine and Lynn Dalgarno. The sequence has also been seen in archaea.