ROLE OF POLYETHYLENEIMINE IN THE PURIFICATION OF RECOMBINANT HUMAN TUMOR-NECROSIS-FACTOR-BETA

The chromatographic behaviour of recombinant human tumour necrosis fac tor beta (rhTNF-beta) (pI similar to 9.0) during cation-exchange chrom atography at pH 7.5 is investigated, Without prior treatment of the Es cherichia coli cell extract with polyethyleneimine (PEI), very little rhTNF-beta was bound to the column. However, upon addition of 5% PEI ( 100 mu l ml(-1)) to the cell lysate, rhTNF-beta was shown to bind to c ation-exchange columns normally. TNF-beta was readily precipitated fro m the clarified cell extract by 20% ammonium sulphate, but only ca, 25 % of this precipitate could be re-solubilized for further purification . However, when 5% PEI was included in the solubilization buffer, the balance of the rhTNF-beta could be recovered. It is proposed that char ge interaction between rhTNF-beta and nucleic acids in the cell extrac t is responsible for both of these anomalous phenomena, and that PEI ( a cationic polyelectrolyte) was able to disrupt this interaction by di splacing rhTNF-beta from the charge complex.