Two independent SILAC-based liquid chromatography-tandem mass spectrometry analyses were performed for identification of BTK interactors in untreated KG-1 cells. Mass-spectrometric data sets were analyzed by MaxQuant software. The proteins listed showed at least fourfold enrichment of heavy peptides compared with light ones. The protein functions listed were obtained by a literature search. Detailed statistics, including total numbers of all peptides identified and quantified, are provided in supplemental Table 3.