Transgenic cyanobacteria constructed as photosynthetic factories producing combined medicines

Abstract

Cyanobacteria are a group of photosynthetic prokaryotes which carry on oxygenic photosynthesis as the same as chloroplasts in eukaryotic algae and plants. Recent 10 years, four cDNA of proteins from human have been transferred into Anabaena sp.7120 and Synechococcus sp.7002 and expressed successfully at our lab. These proteins are as follows: Tumor Necrosis Factor-¦A (TNF-¦A) for anti-cancer, Pro-urokinase(Pro-UK) as thrombolytic agent, Epidermal Growth Factor(EGF) stimulating the proliferation of epidermal cells, and Intestinal Trefoil factor (ITF) protecting the epithelial layer of gastrointestinal tract. The cDNA of TNF-¦A was inserted in the plasmid to result in the shuttle, expression vectors pDC-TNF or pKT-TNF. The cDNA was also ligated with another plasmid to construct an integrative vector. These vectors were transferred into cyanobacteria cells with triparental conjugative transfer method. Southern Blot and Western Blot proved the replication and the expression of TNF-¦A cDNA in these species of cyanobacteria. The cDNA of pro-UK, EGF and ITF transformed the cyanobacteria in the similar way. After changing SD sequence the expression of TNF-¦A cDNA in Anabaena sp.7120 increased from 0.27% to 3.3% based on cellular soluble proteins, measured by radioimmunoassay(RIA). With the elevation of TNF-¦A expresssion the photosynthetic rate and growth of transgenic cells were promoted and greater than in wild cells. Comparing other hosts of foreign gene expression, cyanobacteria as bioreactors or factories possess several advantages: cheap cultivation, no endotoxin mostly, lot of nutrients, oral taking, low activity of proteinases, less problems of intellectual property right. With the development of molecular genetics in cyanobacteria the preparation of recombinant medicines by transgenic cyanobacteria will be applying greatly.