PathHunter β-arrestin1 and 2 EA parental cell lines allow for introduction of your own GPCRs (or other β-arrestin binding protein) and development of your own β-arrestin recruitment assays. PathHunter β-arrestin assays take advantage of DiscoverX’s proprietary enzyme fragment complementation technology. The GPCR (or other β-arrestin binding protein) is fused in frame with a small enzyme donor fragment of β-galactosidase (β-gal) called ProLink™ (PK) which is then co-expressed in the EA parental cell line stably expressing a fusion protein of β-arrestin with a larger fragment of β-gal called enzyme acceptor (EA). Activation of the GPCR-PK (or other PK-tagged β-arrestin binding protein), which induces binding to the β-arrestin-EA fusion protein, forces complementation of the two β-gal enzyme fragments, resulting in the formation of an active β-gal enzyme. Addition of PathHunter detection reagents results in generation of a chemiluminescent signal, allowing the interaction of β-arrestin with GPCR or β-arrestin binding protein to be detected.