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 of the Sm proteins and the U2 and U5 snRNP-specific proteins obtained by spectral count, SILAC, and iTRAQ. The B:C ratios are shown for the Sm proteins (A), the U2 snRNP-specific proteins (B), and the U5 snRNP specific proteins (C). Ratios of proteins in B versus C complex are plotted on a logarithmic scale; error bars, SD between the two biological replicates. “1” indicates that a protein is present in these complexes in a 1:1 ratio. The different shading of the bars represents the ratios of proteins in B and C complexes derived from the values obtained by SILAC, iTRAQ, and spectral count, respectively (see Table 1; Supplemental Tables).