Optical protein sensors that enable to detect relevant biomolecules of interest play central roles in biological research. Coupling fluorescent reporters to protein sensing units has enabled the development of a wide range of biosensors that recognize analytes with high selectivity. In these sensors, analyte recognition induces a conformational change of the protein sensing unit that can modulate the optical signal of the fluorescent reporter. Here, we explore various designs for the creation of tunable allosteric-like fluorogenic protein sensors through incorporation of sensing protein units within the chemogenetic fluorescence-activating and absorption-shifting tag (FAST) that selectively binds and stabilizes the fluorescent state of 4-hydroxybenzylidene rhodanine (HBR) analogs. Conformational coupling allowed us to design analyte-responsive optical protein sensors through allosteric-like modulation of fluorogen binding.