Construction and optimization of a family of genetically encoded metabolite sensors by semirational protein engineering.

A family of genetically-encoded metabolite sensors has been constructed using bacterial periplasmic binding proteins (PBPs) linearly fused to protein fluorophores. The ligand-induced conformational change in a PBP allosterically regulates the relative distance and orientation of a fluorescence resonance energy transfer (FRET)-compatible protein pair. Ligand binding is transduced into a macroscopic FRET observable, providing a reagent for in vitro and in vivo ligand-measurement and visualization.