Disclosed are fusion proteins comprising two detection portions and a periplasmic binding protein (PBP) portion between this two detection portions which undergoes a conformational change upon binding of a compound. Also described are nucleic acid molecules comprising a nucleotide sequence encoding such a fusion protein as well as expression cassettes, vectors, transgenic plants and transgenic non-human animals comprising said nucleic acid molecules. In addition, described are methods for detecting an analyte in a sample or in a cell using said fusion protein, and optionally, a control sensor allowing a calibration of analyte detection made by said fusion protein. Also described are such control sensors and nucleic acid molecules encoding them, as well as diagnostic compositions, kits and uses of the fusion protein and the control sensor for in vitro or in vivo analyte detection and preparing a diagnostic composition.