Preparation and interaction mechanism analysis of single-chain fragment variables against phenylethanolamine A

Abstract

This is the first report on the screening, expression, and recognition mechanism analysis of single-chain fragment variable (scFv) against phenylethanolamine A (PEAA), a newly emerged β-adrenergic agonist illegally used as a feed additive for growth promotion. The PEAA-specific scFv scFv, called scFv-32, was screened from hybridoma cell lines by phage display and was found to be optimally expressed in the E. coli system. The ic-ELISA results revealed an IC50 value of 10.34 μg/L for scFv-32 and no cross-reactivity with other β-adrenergic agonists. Homology modeling and molecular docking revealed the key binding sites VAL178, TYP228, and ASP229. One hydrogen bond, two pi-sigma bonds, and one pi-pi bond maintain the formation of the antibody‒drug complex. Alanine scanning mutagenesis of the three predicted key binding sites showed that the mutants completely lost their recognition activity, which confirmed the accuracy of the theoretical analysis. These results are valuable for the preparation of scFvs and the analysis of the molecular recognition mechanism of antigen-antibodies. Graphical abstract