A sequence of five to nine (typically seven) nucleotides preceding the start codon in prokaryotic messenger RNA (mRNA) that is recognized by the ribosome as the correct site for binding the mRNA molecule prior to the start of translation. The sequence (AGGAGGU) binds a complementary sequence on the 16S ribosomal subunit, helping to form a stable complex between the ribosome and mRNA. The role of this sequence was first proposed by John Shine (1946– ) and Lynn Dalgarno (1935– ).