[Construction of shuttle expression vector and expression of thymosin alpha 1 in Synechococcus sp. PCC7942].

The shutter expression vector pPREUT was constructed from the plasmid pPRS-1 containing the endogenous small plasmid of Plectonema boryanum. The expression elements such as heat shock gene groESL promoter, foreign gene Ub-thymosin alpha 1, rbcS polyA terminator and Kanamycin resistance gene were all included. The shutter plasmid pPREUT was directly transferred into Synechococcus sp. PCC7942. The transformants were obtained through Kanamycin screening. Southern blotting analysis showed that the shutter plasmid have been transferred into Synechococcus sp. PCC7942. After induction by heat shock(42 degrees C) for 30 min, the foreign protein UB-T alpha 1 was expressed efficiently, which reached 7.5% of total amount protein.