CONTROLLED HIGH-LEVEL EXPRESSION OF THE LON GENE OF ESCHERICHIA-COLI ALLOWS OVERPRODUCTION OF LON PROTEASE

Lon protease from Escherichia coli is an ATP-dependent protease which plays important roles in regulating the levels of specific proteins an d in eliminating abnormal proteins. A major problem of working with Lo n protease, the inability to substantially overproduce the enzyme, has been overcome by placing the ion gene under the control of an inducib le trp promoter within a copy-number-controllable plasmid. Induction r esulted in higher levels of production of the protease (similar to 100 mu g/ml of cell culture) than were previously possible. The enzyme ha s been purified to apparent homogeneity and shown to possess the chara cteristic ATP-dependent proteolytic activity. Sequence verification du ring DNA manipulations revealed differences from two previously publis hed sequences for the ion gene.