Abstract

Human protease inhibitor nexin-I(NX-I) cDNA(1.2Kb) was isolated from human lung cDNA library and expressed under the control of T7 promoter as a fused protein in Escherichia coli BL21 and E. coli GJ1158 by addition of IPTG and Nacl as inducers. For GJ1158, 300 mM NaCl was added for induction after the cell reached A_600=0.6. As a result, E. coli GJ1158 showed higher expression level than BL2l with lesser extent of inclusion bodies. The optimum concentration of NaCl exerting no induction effect but shortening the time to reach A_600=0.6 was 50 mM. All the results suggested that E. coli GJ1158 was a useful host for efficient expression of NX-I using NaCl as an inducer. The expressed NX-1 showed an inhibitory effect on thrombin activity. The expressed protein was purified by immobilized metal affinity column chromatography (IMAC) and characterized by digestion with enterokinase (EK).

• Keywords: Protease inhibitor; nexin-I; cloning; expression; inducer; inclusion body; IMAC; mature form