Engineering regulable Escherichia coli beta-galactosidases as biosensors for anti-HIV antibody detection in human sera

The activity of engineered, peptide-displaying enzymes is modulated by bind ing to specific anti-peptide antibodies. This new concept of a quantitative antibody detection system allows test kits to be set up for fast diagnosis of infectious diseases. To develop a quick and homogeneous assay for the d etection of human immunodeficiency virus (HIV) infection, we have explored two acceptor sites of the bacterial Escherichia coli beta -galactosidase fo r the accommodation of HIV antigenic peptides. Two overlapping epitopes (na mely P1 and P2) from the gp41 envelope glycoprotein, contained in different sized peptides, were inserted in the vicinity of the enzyme active site to generate a set of hybrid, enzymatically active beta -galactosidases. Regul able enzymes of different responsiveness to monoclonal antibody binding wer e generated with both acceptor sites tested. These biosensors were also sen sitive to immune sera from HIV-infected patients. Modeling data provide ins ight into the structural modifications in the vicinity of the active site i nduced by peptide insertion that strongly affect the responsiveness of the engineered proteins through different parameters of their catalytic propert ies.