The invention relates to the use of a fluorescent protein chosen in particular from autofluorescent proteins, for the detection of the non-covalent interactions between a target protein labeled with the fluorescent protein and one of its ligands labeled with a label consisting: either of a molecule which is capable of absorbing the light emitted by the fluorescent protein, or of a fluorescent substance, this detection taking place by fluorescence energy transfer: between the fluorescent protein and the above-mentioned fluorescent substance, the fluorescent substance being such that either it is excitable at the emission wavelength of the fluorescent protein, or it emits at the excitation wavelength of the fluorescent protein, or between the fluorescent protein and the above-mentioned molecule which is capable of absorbing the light emitted by the fluorescent protein.