The Tag:LBD(FSHR) entry in FlyBase represents the ligand-binding ectodomain of the Homo sapiens FSHR gene (HGNC:3969). Together, Tag:LIG(CGA) and Tag:LIG(FSHb) form a heterodimer that acts as a specific ligand for Tag:LBD(FSHR). If the ligand-binding ectodomain of a receptor of interest is replaced with Tag:LBD(FSHR) and the receptor-binding domain of the corresponding ligand is replaced with Tag:LIG(FSHb), then binding of the chimeric receptor and ligand can be reconstituted in a conditional manner by providing or removing a source of Tag:LIG(CGA). This property can used to study the mechanisms of signal transduction (FBrf0237506).