PRODUCTION AND SIMPLE PURIFICATION OF A PROTEIN ENCODED BY PART OF THE GAG GENE OF HIV-1 IN THE ESCHERICHIA-COLI HB101F(+) EXPRESSION SYSTEM INDUCIBLE BY LACTOSE AND ISOPROPYL-BETA-D-THIOGALACTOPYRANOSIDE

The development of the Escherichia coli expression system, which was prepared by transferring the F' episome from strain 71/18 to a highly transformable F- strain HB101, is described. These new HB101 (F+) cells, which produced high levels of lac repressor, were capable of taking up lactose and grew under strict selection conditions. A relatively simple two-step purification of part of a protein (M(r) 27 000) encoded by the gag gene of HTV-1 in this expression system is described. The supernatant prepared by removal of cell debris was precipitated by 30% saturation of ammonium sulphate. The protein spectrum was characterized by gel electrophoresis, immunoblotting and ion-exchange titration curves. Optimum separation was achieved using a strong anion exchanger (Mono Q) at pH 8.0. The purified protein did not cross-react with antibodies to E. coli.