Modeling of Chimeric β-galactosidase Antigenic Fusion Proteins

It has been shown that the insertion of antigenic peptides of the foot-and-mouse disease virus (FMDV) into specific sites of the bacterial enzyme β-galactosidase causes a severe reduction of the activity of this enzyme which can be recovered upon antibody binding to the inserted antigenic peptide [1]. In principle, the recovery of β-galactosidase activity upon antigen-antibody binding allows the detection of antibodies by simple colorimetric quantification of β-galactosidase activity in a homogeneous test system, involving only the antigenic fusion protein, a chromogenic substrate and a serum sample for testing. The lack of three-dimensional (3D) structural information on the chimeric proteins renders their modeling requisite to understand at the molecular level the chimeric enzyme inactivation and reactivation upon antibody binding. For this purpose, we have determined 3D models of chimeric β-galactosidase by comparative modeling and structure prediction techniques.