A FlAsH–Tetracysteine Assay for Quantifying the Association and Orientation of Transmembrane α-Helices



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Lighting up protein dimers in membranes: The association of membrane proteins plays a critical role in biology. We describe a FlAsH–tetracysteine (tC) assay that detects protein dimerization in lipid bilayers with a fluorescent readout. The stringent spatial requirement of FlAsH–tC complex formation readily differentiates helix dimers in parallel and antiparallel orientations.