Substrates of human TRAP complex

While the Sec61-complex in the membrane of the human endoplasmic reticulum facilitates translocation of all precursor polypeptides with amino-terminal signal peptides or transmembrane helices, the Sec61-associated translocon-associated protein (TRAP)-complex supports translocation of only a subset of precursor polypeptides, i.e. in a substrate-specific manner. To characterize TRAP-dependent precursors, we combined siRNA-mediated TRAP depletion in HeLa cells, label-free quantitative proteomics, and differential expression analysis. Sec61 served as a positive control