For mass spectrometry analysis of SEC14L2 and STMN1 binding partners, 293T cells expressing SEC14L2-Flag or STMN1-Flag were lysed in NP-40 lysis buffer. The cytosolic proteins were collected by centrifugation and incubated with anti-Flag beads for 2 h, followed by five washes with NP-40 lysis buffer. Bound proteins were then eluted using 0.1 M glycine, subjected to mass spectrometry analysis.