<P> The Shine - Dalgarno (SD) sequence is a ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG . The RNA sequence helps recruit the ribosome to the messenger RNA (mRNA) to initiate protein synthesis by aligning the ribosome with the start codon . </P> <P> The Shine - Dalgarno sequence exists both in bacteria and archaea . It is also present in some chloroplast and mitochondrial transcripts . The six - base consensus sequence is AGGAGG; in Escherichia coli, for example, the sequence is AGGAGGU, while subsequence GAGG dominates in E. coli virus T4 early genes . </P> <P> The Shine - Dalgarno sequence was proposed by Australian scientists John Shine and Lynn Dalgarno . </P> <P> Using a method developed by Hunt, Shine and Dalgarno showed that the nucleotide tract at the 3' end of E. coli 16S ribosomal RNA (rRNA) is pyrimidine - rich and has the sequence - PyACCUCCUUA 3' OH . They proposed that these ribosomal nucleotides recognize the complementary purine - rich sequence AGGAGGU, which is found upstream of the start codon AUG in a number mRNAs found in viruses that affect E. coli . Many studies have confirmed that base pairing between the Shine - Dalgarno sequence in mRNA and the 3' end of 16S rRNA is of prime importance for initiation of translation by bacterial ribosomes . </P>

In the figure below which label represents the shine delgarno site