We generated a HEK293 cell line expressing ZZ-TEV-FLAG-bait protein by Lipofectamine 3000 transfection. The expression level of bait protein is controlled to endogenous level by addition of 2 ng/mL doxycycline. Note the combined treatment of Torin1 and CQ was applied for STX17. The tandem affinity purification of tagged bait protein was performed in a physiology buffer condition [20 mM Tris-HCl (pH 7.5), 150 mM NaCl, 0.5% Igepal CA-630, 1 mM EDTA, protease inhibitor cocktail (Roche)]. The eluted protein mixtures were subjected to SDS/PAGE and further analyzed by mass spectrometry.