Both the full-length and SH fragment of PLCγ1 drive LAT clustering. (A) TIRF microscopy revealed LAT microcluster formation with the full-length or SH2-SH2-SH3 domain of PLCγ1. Alexa Fluor 488–labeled, phosphorylated LAT at 300 molecules/µm² was incubated with 250 nM Sos1 and indicated concentrations of PLCγ1 or fragment. Scale bar, 5 µm. (B) Quantification of PLCγ1-driven LAT microclusters. Shown are mean ± SD; n = 3 independent experiments. (C) Recombinant proteins used in this study. Purified proteins were applied to SDS-PAGE, followed by Coomassie blue staining.