A RECOMBINANT HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 CAPSID PROTEIN (RP24) - ITS EXPRESSION, PURIFICATION AND PHYSICOCHEMICAL CHARACTERIZATION

An expression system has been established in Escherichia coli to facil itate the preparation of the HIV-1 capsid protein in amounts sufficien t for structural analysis. A plasmid vector pTCA5, containing the gene for the recombinant HIV-1 capsid protein rp24 under the control of th e lambda-P-R-promoter, was constructed which gave an expression produc t that spanned 234 amino acid residues. It differs at the N-terminus f rom the authentic sequence in that the residues Pro-Ile- are replaced by Met-Asn-Ser-Ala-Met-. Recombinant p24 was produced, as inclusion bo dies in E. coli LE392 containing pTCA5, at a level of approximately 15 % of the total cellular protein. After dissolution of the inclusion bo dies in the acidic urea system, the protein was easily reconstituted i n a soluble state by dialysis. The yield of reconstituted and purified protein was 12 mg per liter in rich medium. Recombinant rp24 consists of about 40% alpha-helix and 10% beta-sheet from circular dichroism m easurements and the two cysteine residues, within the rp24 sequence, a re bridged by a disulfide bond.