Expression of human lymphotoxin alpha in Aspergillus niger

A gene-fusion expression strategy was applied for heterologous expression o f human lymphotoxin alpha (LT alpha) in the Aspergillus niger AB1.13 protea se-deficient strain. The LT alpha gene was fused with the A. niger glucoamy lase GII-form as a carrier-gene, behind its transcription control and secre tion signals. Special attention was paid to the influence of different codo n usage on secretion of protein. In the case of human tumor necrosis factor alpha (TNF alpha) a dramatic change of secretion has been observed when hu man cDNA sequence was used instead of synthetic E. coli biased codons. In t he case of LT alpha such a change of codon usage brought improvement at the RNA level, however, no increase in the quantity of secreted protein was ob served, due to the proteolitic activity of the host organism. The estimated yield of secretion of LT alpha from A. niger into the soya medium was 50 p g l(-1) of culture.