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Figure 3 | Proteome Science

Figure 3

From: Vigilin interacts with signal peptide peptidase

Figure 3

Representative CID spectra documenting specific co-enrichment of vigilin with SPP and non-specific co-purification of HSP70. Parallel co-purification with pre-saturated or naive anti-SPP antibody was followed by iTRAQ-based quantitation and ESI-MS/MS analyses. iTRAQ labeling reactions were setup with the iTRAQ116 label as the negative control, and iTRAQ117 label as peptides derived from the SPP-specific purification. (A) CID spectrum assigned to tryptic peptide AQFEGIVTDLIR which contributed to the identification of HSP70. iTRAQ signature mass peak ratios documented that this peptide was contributed equally by negative control and specific IP eluates. (B) Representative CID spectrum assigned to vigilin-derived peptide EQLAQAVAR which exhibited a strongly skewed iTRAQ ratio, demonstrating that this peptide was primarily contributed by the specific sample. Graphs on the side depict expanded views of the isotopic envelope of the respective precursor masses and the iTRAQ signature mass peaks. (C) Human vigilin amino acid sequence (GenBank: NP_005327.1) with peptides identified by MS/MS are in red and the 14 KH domains are underlined.

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