Tag:LOV(VfAU1) corresponds to the light-oxygen-voltage (LOV) sensing domain of the Vaucheria frigida aureochrome 1 gene (GB:AB252504, PMID:18002911). In the dark, Tag:LOV(VfAU1) is largely monomeric, while illumination with blue light induces Tag:LOV(VfAU1) to form a homodimer (PMID:21641326). This property can be used to induce dimerization of a tagged protein of interest in vivo. The small size of the Tag:LOV(VfAU1) domain together with its slow relaxation from light-activated to dark-adapted state make Tag:LOV(VfAU1) particularly useful as a tag for activation of membrane receptors by light-induced forced dimerization (PMID:24986882).