EXPRESSION OF THE GENE FOR HOMOSERINE KINASE OF ESCHERICHIA-COLI IN MAMMALIAN-CELLS

The thrB gene of E. coli coding for homoserine kinase [EC 2.7.1.39] wa s introduced into the pRc/RSV mammalian expression vector. Transfectio n of the CHO cell line with the resulting pRSV-Bneo plasmid by electro poration yielded a stably transformed clone accumulating o-homoserine phosphate. Assay for homoserine kinase in cell extracts revealed enzym e activity of 6.0 . 10(-3) units per mg protein, which was 75% that in E. coli cells cultured in the minimal medium and about 20 times that in the 3T3 clones obtained before.