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

The development of the Escherichia coli expression system, which was p repared by transferring the F' episome from strain 71/18 to a highly t ransformable 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 si mple 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 s upernatant prepared by removal of cell debris was precipitated by 30% saturation of ammonium sulphate. The protein spectrum was characterize d by gel electrophoresis, immunoblotting and ion-exchange titration cu rves. Optimum separation was achieved using a strong anion exchanger ( Mono Q) at pH 8.0. The purified protein did not cross-react with antib odies to E. coli.