EXPRESSION OF THE EXTRACELLULAR DOMAIN OF THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENVELOPE PROTEIN AND ITS FUSION WITH BETA-GALACTOSIDASE IN SACCHAROMYCES-CEREVISIAE

Two envelope glycoprotein gene fragments were cloned from the proviral genome of the HXB2 isolate of human immunodeficiency virus (HIV). For the production of the two domains of the envelope gene product these cloned gene fragments were inserted into an Escherichia coli-yeast ind ucible shuttle vector fused to the galactokinase (GAL1) promoter. Cell extracts from strains of Saccharomyces cerevisiae harboring these two vectors (pYENV1 and pYENV2) were found to contain a specific protein with a size of 50 kDa when induced by galactose, while the protein cou ld not be detected in extracts from control cells containing only the E. coli-yeast vector in the presence of galactose. Furthermore, anothe r expression plasmid coding for fusion proteins from the majority of t he external envelope glycoprotein (gp120) moiety and a large part of t he beta-galactosidase was constructed. Antibodies from HIV type 1-posi tive sera could react with recombinant fusion polypeptides. Transforma nts could produce this fusion protein to a level of about 1.6% of the total protein content, as deduced from beta-galactosidase activity.