Synthesis of frataxin genes by direct assembly of serial deoxyoligonucleotide primers and its expression in Escherichia coli

Frataxin, a small nuclear-encoded protein targeted to mitochondria, is known to play an important role in both the mitochondrial respiratory chain and iron homeostasis. The protein is highly conserved in most eukaryotic organisms with no major structural changes, suggesting that it serves a crucial function in all organisms. Recently, purified frataxin was used as a therapeutic treatment of Friedreich's ataxia, a common degenerative disorder that results from a frataxin protein deficiency, by directly applying the protein to the diseased cells. In this report, we describe a novel and rapid method of synthesizing genes encoding frataxin proteins for the purpose of efficient protein production. The artificial yeast and human frataxin genes were synthesized by direct assembly of serial deoxyoligonucleotide primers designed based on the optimal nucleotide sequences. When we tested the expression of these synthetic genes in two E. coli host strains, the yeast frataxin gene was expressed 20 folds higher in Rosetta (DE3) cells than in BL21 (DE3) cells, whereas the expression levels of human frataxin were similar in both E. coli strains. Attenuation of the Fenton reactions by the purified yeast and human frataxin proteins was observed under the defined conditions, which suggests that the recombinant frataxin proteins are active and functional. The procedure described here could be applied to many known genes or to generate novel synthetic genes that can be redesigned by arranging functional domains from previously identified genes and to study the structure and function of synthetic recombinant proteins and potential usage.