Difference between Shine-Dalgarno and Kozak Sequence

Shine-Dalgarno and Kozak sequences are consensus sequences that help in the initiation of translation in prokaryotes and eukaryotes. Translation is the process of synthesis of proteins by the ribosomes. It takes place in three steps: initiation, elongation and termination.

In translation, mRNA is decoded with the help of tRNA to synthesize proteins.

Shine-Dalgarno Sequence

The Shine-Dalgarno sequence is named after the Australian scientists John Shine and Lynn Dalgarno. It is a ribosomal binding site in bacterial and archeal mRNA. It is located 8 bases upstream of the start codon AUG. The sequence recruits ribosomes to the mRNA that initiates protein synthesis by aligning the ribosomes with the start codon.

The Shine-Dalgarno sequence in E.coli is 5’AGGAGGU3’.

Kozak Sequence

The Kozak sequence is named after the scientist Marilyn Kozak who discovered it. It is a nucleic acid motif that initiates protein translation in eukaryotic mRNA.

A start codon is located within the Kozak sequences where the assembly of ribosomes begins. This sequence is integral in protein regulation and the overall health of the cells.

The Kozak sequence is 5’(gcc)gccRccAUGG-3’, where R is a purine; capital letters are conserved bases and small letters are variable bases.

The differences between Shine-Dalgarno and Kozak sequences are tabulated below.

Shine-Dalgarno sequence

Kozak sequence


The Shine-Dalgarno sequence is a ribosomal binding site found commonly in bacterial but rarely in archeal mRNA.

The Kozak sequence is a protein translation initiation site in eukaryotic mRNA.

Discovered by

It was discovered by John Shine and Lynn Dalgarno.

It was discovered by Marilyn Kozak.




Start codon

It is located 8 bases upstream of the start codon.

The start codon is present in the Kozak sequence.


It is found in prokaryotes only.

It is found in eukaryotes only.

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Frequently Asked Questions


Where is the Kozak sequence?

A Kozak sequence is found in the eukaryotic mRNA.

What is the purpose of the Kozak sequence?

The Kozak sequence plays an important role in the initiation of the translation process.


When was the Kozak sequence discovered?

The Kozak sequence was discovered in 1987.


What is a nucleic acid motif?

A motif is a nucleic acid sequence pattern that holds some biological significance.


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