Mass spectrometry–based relative quantification of proteins in precatalytic and catalytically active spliceosomes by metabolic labeling (SILAC), chemical labeling (iTRAQ), and label-free spectral count

Relative protein abundances in the B and C complexes for the U1, U4/U6, and U4/U6.U5 snRNP-specific proteins and the LSm proteins, as obtained by SILAC, iTRAQ, and spectral count. (A) B:C ratios for U1 snRNP-specific proteins. No protein ratios were obtained for U1-C from the spectral count since this protein was completely absent from the C complex. (B) B:C ratios for the U4/U6- and U4/U6.U5-specific proteins. (C) B:C ratios for the LSm proteins. No protein ratio was obtained from the spectral count for LSm4 since this protein was absent from the C complex. LSm5 was not identified or quantified. For details, see legend to Figure 3.