Abstract
The Insulin-like Growth Factor 1 (IGF1) is a small (~ 7.6 kDa) protein-hormone primarily generated in the liver of mammals. It has a similar structure to insulin, and functions to support cell growth and development. As a result, IGF1 is in high demand in the biopharmaceutical, biomedical, and research fields. In eukaryotic photosynthetic systems, over-expression of this and other proteins has been met with limited success. The current study used Synechocystis sp. PCC 6803, a freshwater, single-celled cyanobacterium, as a host system to produce the IGF1 through recombinant DNA technology. To stabilize and enhance IGF1 accumulation in the cells, fusion constructs of the codon optimized IGF1 gene with the β-subunit ( cpcB gene) of phycocyanin were designed. The resulting transgenic strains accumulated significant amounts of recombinant IGF1 in direct proportion to phycocyanin in Synechocystis . Quantitative aspects of the work, including the culture biomass yield in photoautotrophic and mixotrophic growth conditions, and the amount of recombinant fusion protein (CpcB*IGF1), as a fraction of total cellular protein in Synechocystis are reported. Further, antibody specificity is used as a tool to examine the effect of different fusion orientations between the CpcB and IGF1 proteins, needed to inform of optimal conditions for IGF1 functional properties. The work adds to the concept of cyanobacteria serving as cell factories for the renewable photosynthetic generation of biopharmaceutical proteins from sunlight, carbon dioxide and water.