Extracellular production of human tumor necrosis factor-alpha by Escherichia coli using a chemically-synthesized gene

A DNA fragment of approximately 490 base pairs encoding human TNF was chemically synthesized and expressed within Escherichia coli cells. Furthermore, extracellular production of human TNF and several N-terminal deletion mutants of TNF was attempted using the excretion vector pEAP8. The TNF mutant with two N-terminal amino acids deleted (N delta 2-TNF) was efficiently excreted into the culture medium by E. coli carrying the plasmid pEXTNF3. In this clone, the signal peptide was correctly processed during the excretion. The E. coli-excreted N delta 2-TNF had higher antitumor activity than wild-type TNF or N delta 2-TNF produced intracellularly by E. coli.