A rapid and sensitive bacterial assay to determine the inhibitory effect of 'interface' peptides on HIV-1 protease co-expressed in Escherichia coli.

The HIV-1 protease is essential for maturation of virus particles and is, therefore, an attractive target for antiviral drugs. The function of this protease depends on the dimerization of two identical subunits. Commonly used protease inhibitors are directed mainly against the active site of the enzyme which often leads to viral resistance. To determine the inhibitory effect of peptides interfering with the dimerization site of the HIV-1 protease, a recombinant bacterial screening assay was established. Escherichia coli was co-transformed with two different plasmids, expressing the 'interface' peptide and an active HIV-1 protease toxic for the bacteria. Co-expression of inhibitory peptides overcomes the incomplete membrane transmission of supplemented inhibitors and leads to a direct interaction of the inhibitory peptide and the HIV-1 protease. The inhibitory effect of co-expressed peptides was measured by an increased growth of co-transformed bacteria, compared with a slowly growing E. coli control culture only expressing the HIV-1 protease. Using this assay several penta- and hexa-peptides were screened for their ability to inhibit HIV-1 protease activity. One of these peptides showed a significant inhibitory effect on co-expressed recombinant HIV-1 protease.