MAST1 was N-terminally EGFP-tagged and overexpressed in HEK293 cells. Various constructs of MAST1, including WT, S90A, S161A, S90A S161A, and N-terminal truncations spanning S90 and S161 were compared in a pairwise manner to identify specific interactors of MAST1. EGFP-MAST1 was immunoprecipitated using the GFP-Trap system and the immunoprecipitates analyzed by mass spectrometry.