Crystallizable HIV-1 protease derived from expression of the viral pol gene in Escherichia coli

A plasmid vector was used to express the HIV-1 pol open reading frame under the regulation of the bacterial trp promoter in Escherichia coli. This expression system has been used as a source of recombinant viral protease. The self-processed active enzyme was recovered from a soluble fraction of a bacterial cell lysate and purified by a procedure involving four steps of chromatography. The protocol yielded 0.3 mg of protease for each liter of bacterial culture. The protease formed tetragonal bipyramidal crystals which have been used in high-resolution X-ray diffraction studies.