| Human prothymosinα( ProTα) is a highly acidic protein which is distributed widely and conserved highly among mammals. Its molecular weight is 13 kDa. ProTαhas been tested in clinical trial as an immunomodulator. Interleukin-2 (IL-2) which is 15kDa and acts as a immunocyte growth factor can augment natural killer cell activity .So it is a powerful immunoregulatory lymphokine and has been used in treat cancer, but it may bring about side effect if overused .The combination of IL-2 and prothymosin alpha (Proα) can increase anti-tumor effect compared with IL-2 alone. The combination of IL-2 and ProTαcan also decrease toxiferous side effect caused by IL-2 .In this research,the ProTα-IL-2 fusion protein gene was amplified by PCR with speific primers which were designed for prokaryotic expression .Then the amplified gene fragment was subcloned into the expression vector pET42a.There are 13 rare codes existing dispersively in the opening reading frame of fusion protein. So E.coli Rossetta has been chosen as the host, because it can supply with the tRNAs of rare codes. The cloned fusion protein gene is expressed solubly after IPTG induction. Experimenting by SDS-PAGE and Western blotting detection, it has been proved that the amino acid sequence of expressed fusion protein is correct .The soluble fusion protein has been purified through DEAE-Sepharose F.F chromatography. The fusion protein has both the activity of Prothymosin and that of IL-2 in terms of E-rosette assay and interleukin-2-dependent CTLL-2 active test.The results of study provide a basis for developing new drug of ProTα- IL2 fusion protein.
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