Optimizing protein expression in heterologous system: Strategies and tools

Abstract

Heterologous expression involves the introduction of gene encoding for a protein of interest from one species into the cell of another species, thus allowing for the host cells to express the foreign protein. Often, heterologous expression can result in very low protein expression in the host cells. For optimal heterologous gene expression, numerous factors such as the codon usage of the recipient species, guanine and cytosine (GC) composition, Kozak sequence, Shine-Dalgarno sequence, messenger ribonucleic acid (mRNA) stability, and splicing pattern of the gene have to be examined. Codon usage is the most important factor to be considered for higher expression especially when gene-donor and gene-recipient species belong to a prokaryote and eukaryote or vice versa. It is imperative to modify the codon to match the usage pattern of recipient species for maximal protein expression. Cryptic splice sites, premature polyadenylation signal and destabilizing sequences in the mRNA also need to be removed for higher protein yield. Presently, many tools are available to modify native gene or design synthetic version for higher and stable expression in plants, animals or any prokaryotic host species. In this review, we have discussed the different factors to be considered while synthesizing or modifying a gene for optimal expression in heterologous host species. Finally, we have also listed various tools and software available for standardizing heterologous gene expression.