The Shine-Dalgarno sequence (AGGAGG), proposed by Australian scientists John Shine and Lynn Dalgarno,[1] is a ribosomal binding site located upstream of the start codon AUG. It is a consensus sequence that helps recruit the ribosome to the mRNA to initiate protein synthesis by aligning it with the start codon. The complementary sequence (CCUCCU), is called the anti-Shine-Dalgarno sequence and is located at the 3' end of the 16S rRNA in the ribosome.
Mutations in the Shine-Dalgarno sequence can reduce translation. This reduction is due to a reduced mRNA-ribosome pairing efficiency, as evidenced by the fact that complementary mutations in the anti-Shine-Dalgarno sequence can restore translation.
When the Shine-Dalgarno sequence and the anti-Shine-Dalgarno sequence pair, the translation initiation factors IF2-GTP, IF1, IF3, as well as the initiator tRNA fMet-tRNA(fMET) are recruited to the ribosome.
Shine-Dalgarno sequence vs. ribosomal S1 protein
In Gram-negative bacteria, however, Shine-Dalgarno sequence presence is not obligatory for ribosome to locate initiator codon, since deletion of Anti-Shine-Dalgarno sequence from 16S rRNA doesn't lead to translation initiation at non-authentic sites. Moreover, numerous prokaryotic mRNAs don't possess Shine-Dalgarno sequences at all. What principally attracts ribosome to mRNA initiation region is apparently ribosomal protein S1, which binds to AU-rich sequences found in many prokaryotic mRNAs 15-30 nucleotides upstream of start-codon. It should be noted, that S1 is only present in Gram-negative bacteria, being absent from Gram-positive species
在革蘭氏陰性細菌中,Shine-Dalgarno序列對核糖體定位起始密碼子不是必須的,從16 s rRNA刪除Anti-SD序列後不會導致隨機翻譯(大概是這意思吧)。此外,大量原核生物的mRNA並不具有SD序列。將核糖體吸引至mRNA翻譯起始區域,主要靠核糖體S1蛋白,它與mRNA起始密碼子上游15~30鹼基的富AU區域結合。這樣的富AU區域存在於大量原核生物的mRNA中。值得注意的是,S1隻是出現在革蘭氏陰性細菌中,革蘭氏陽性細菌沒有。