a, Cryo-EM map colored by local resolution as estimated from ResMap. b, Gold Standard Fourier Shell Correlation (GSFSC) of the final map used for model building from CryoSPARC2 with a reported resolution of 3.10 Å. c, Directional FSCs calculated by 3DFSC server. Map sphericity was calculated to be 0.949.d, Workflow for processing the HER2/HER3/NRG1β/trastuzumab dataset. The final model is indicated with a red box. e, Cryo-EM map colored by local resolution as estimated from ResMap. f, Gold Standard Fourier Shell Correlation (GSFSC) of the final map used for model building from CryoSPARC2 with a reported resolution of 3.45Å. g, Directional FSCs calculated by 3DFSC server. Map sphericity was calculated to be 0.941.