Recombinant Production and Purification of Inosine 5-Mono Phosphate Dehydrogenase 1 Retinal Isoforms for Functional Studies

Inosine 5-monophosphate dehydrogenase 1 (IMPDH1) is the rate-limiting enzyme in the de novo purine nucleotide biosynthesis. IMPDH1 catalyzes IMP-oxidation to XMP, which in continue is converted to guanine nucleotides. Like mammals, the mouse IMPDH1 (mH1) has retinal-specific isoforms named H1 (546) and H1 (603). Mutations in the IMPDH1 gene are believed to cause retinal degenerative disease, retinitis pigmentosa, mediated by retinal-specific gene variants. After RNA extraction from the mouse retina, RT-PCR was done using NdeI and XhoI harboring primers. Tree mH1 isoform genes were amplified and cloned into a pET26b+ vector separately. The recombinant expression vectors were then transformed in E. coli BL21 (DE3) strain, expressed under IPTG-induced conditions and purified with Ni-NTA agarose resin. Activity assay of recombinant proteins was done by using spectrophotometric methods. Here, we cloned and optimized the expression and the purification of recombinant mH1 canonical and retinal isoforms in E. coli to gain soluble and highly active protein for further functional assays. Recombinant protein production in prokaryotic hosts, especially E. coli, is the most common method in large-scale of protein production for functional and structural studies. However, maximal yield and activity of recombinant proteins require optimal conditions for expression and purification, which is what we showed in the present study for the mouse IMPDH1 recombinant isoforms.