What is codon optimization and why is it important?
Living cells use a set of rules called the “genetic code” to translate genetic information encoded in DNA and mRNA into proteins. The code consists of nucleotide triplets, called codons, that specify which amino acid should be added to the growing chain of a peptide during protein synthesis.
There are 64 different codons. 61 of them encode the 20 standard amino acids, while another 3 function as stop codons. The greater number of codons relative to the number of amino acids they code for, means that a single amino acid can be encoded by more than one codon. Indeed, some common amino acids, such as arginine and leucine, are encoded by as many as 6 codons.
Different organisms exhibit bias towards use of certain codons over others for the same amino acid. Some species are known to avoid certain codons almost entirely. Why such biases exist and the effect they have on protein expression are still subject to debate in the fields of molecular evolution and biotechnology; however, they can impact expression significantly. Therefore, it is important to consider codon optimization when performing expression studies.
While numerous factors contribute to the success of protein expression, codon optimization plays a critical role, particularly when proteins are expressed in a heterologous system. As an example, if a human gene is to be expressed in E. coli, choosing codons preferentially used by the bacterium can increase the success of protein expression [1,2]. This is particularly true when rare codons are eliminated.
Studies also show that translationally efficient codons can increase elongation rate, accuracy of translation, or both . However, it is noteworthy that there are also studies showing no or weak correlations between codon bias and gene expression . These findings suggest that we do not have a comprehensive understanding of the effect of codon usage in all systems. Alternative strategies may have different levels of success in distinct organisms and with different types of expression. While codon optimization can improve protein expression, it does not provide a guarantee.
How does the IDT Codon Optimization Tool work?
The IDT Codon Optimization Tool was developed to optimize a DNA or protein sequence from one organism for expression in another by reassigning codon usage based on the frequencies of each codon’s usage in the new organism. For example, valine is encoded by 4 different codons (GUG, GUU, GUC, and GUA). In human cell lines, however, the GUG codon is preferentially used (46% use vs. 18, 24, and 12%, respectively). The codon optimization tool takes this information into account and assigns valine codons with those same frequencies. In addition, the tool algorithm eliminates codons with less than 10% frequency and re-normalizes the remaining frequencies to 100%. Moreover, our optimization tool reduces complexities that can interfere with manufacturing and downstream expression, such as repeats, hairpins, and extreme GC content.
Other advantages provided by IDT Codon Optimization Tool
The IDT Codon Optimization Tool provides several additional features:
- Input sequence options. You can enter either DNA or amino acid sequences. You can also codon optimize Genes (IDT) or gBlocks Gene Fragments (IDT) reagents.
- Sequence complexity check. You are notified of sequence complexities such as hairpins, repeats, or extreme GC content. The algorithm then provides the best sequence option with minimum complexity.
- Manual optimization capability. You can use manual mode to have full control over the optimization process.
In the following video, Adam Clore, Technical Director of the Synthetic Biology Division at IDT, provides information about the Codon Optimization Tool and related services offered by IDT.
To order codon optimized sequences or obtain more information about the tool, visit Codon Optimization Tool.