Tag:LOVpep is an engineered light-regulated specific binding tool based on the LOV2 flavin binding domain of the Avena sativa Phototropin 1 (PT1) gene. A short peptide epitope (KAVDTWV) has been appended to the C-terminal end of the domain, along with partial truncation of the Jα helix and other mutations selected to improve its utility. The C-terminal peptide epitope can bind to a cognate PDZ domain (such as Tag:ePDZb1), but in the dark, this binding is inhibited due to caging of the epitope by the Jα helix binding to the LOV2 core. Upon blue light irradiation, unfolding of the Jα helix exposes the C-terminal peptide epitope, which can now bind a cognate PDZ domain and form a heterodimer. This property can be used to bring together two tagged proteins of interest in vivo in a light-dependent manner, for example to reconstitute a functional protein by bringing together complementary split system components, or to target a protein of interest to a particular subcellular location (PMID:22388287).

Tag:LOVpep must be used as a C-terminal tag in order for Tag:ePDZb1 to be able to bind it (PMID:22388287).