USE OF A DUAL-ORIGIN TEMPERATURE-CONTROLLED AMPLIFIABLE REPLICON FOR OPTIMIZATION OF HUMAN INTERLEUKIN-1-BETA SYNTHESIS IN ESCHERICHIA-COLI

A new dual-replicon recombinant plasmid, pPR53-tsr, has been constructed; it is derivative of the expression vector pPR-TGATG-1 [Mashko et al., Gene 88 (1990) 121-126]. In contrast to its progenitor, pPR53-tsr is a low-copy-number (low-Cop) plasmid amplifiable in temperature-dependent fashion. In addition to both the replicon and the par locus from plasmid pSC101, providing segregational stability and a low Cop at 28-degrees-C, the new plasmid contains a mutant ColE1 replicon whose RNAII is synthesized under the control of the p(L) promoter. The presence of a thermolabile repressor, cIts857, allows the thermo-inducible amplification of pPR53-tsr; the increased plasmid Cop is estimated at approx. 200 per genome 6 h after thermal induction at 42-degrees-C. Thus, pPR53-tsr can be used as a donor of the thermo-inducible dual-replicon fragment for recombinant plasmids. Here, we employ such an approach for optimization of production of human interleukin-1-beta (hIL-1-beta) in Escherichia coli at a high level. The thermo-induced level of recombinant hIL-1-beta (re-hIL-1-beta) biosynthesis was around 9% of total cellular protein when the dual-replicon high-Cop vector was used. A method based on acidification of the water-soluble protein fraction to pH 4.0 has been developed that allows for the isolation of 80%-pure re-hIL-1-beta. The homogeneous material was obtained by two subsequent hydrophobic sorbent chromatographies. The protein yield ranged between 3-5 mg of re-hIL-1-beta/g of wet cells. The re-hIL-1-beta specific activity was about 2 X 10(8) units/mg, coinciding with that of the authentic hIL-1-beta.