Movie S1

Dual-color SMCT identifies FHC association in live cell plasma membranes. GFP-K^b dimer formation was probed by co-locomotion analysis. Individual GFP-K^b molecules labeled with Rho11 (magenta) and Dy647 (green) in STF1 cells were imaged by TIRF microscopy (scale bar, 2.5 μm; frame rate, 10 Hz; playback speed, 1/3 real time). Movies were acquired in the absence of peptide (FHCs, left), in the presence of peptide (HC/b₂m/peptide complexes; center) and in the presence of peptide and a crosslinker consisting of a dimeric anti-GFP nanobody (right). Localized molecules in each channel are encircled, co-locomoting molecules are highlighted by white diamonds.