Expression of human lysozyme in an insoluble form in yeast

A high level of expression in yeast of a chemically synthesized human lysozyme (hL) gene was achieved by introducing an A-rich DNA fragment just upstream from the ATG start codon. The synthesized recombinant human lysozyme (r-hL) was insoluble and biologically inactive. It was solubilized with 7 M urea (pH 9) from yeast cells and its lytic activity was efficiently regenerated by oxidative renaturation. This renaturation experiment and Western blotting analysis under reducing and non-reducing conditions indicate that the insoluble form might be caused by the formation of incorrect intra- or intermolecular disulfide bonds. The N-terminal amino acid sequence of the purified r-hL was identical with that of authentic hL.