Figure 5.

Mass spectrometric detection of the BRCA2^Δ5+7 protein. (a) Schematic illustration of WT-BRCA2 (upper panel) and BRCA2^Δ5+7 protein (lower panel) with putative unique trypsin digestion sites. Amino acid sequence derived for the shifted reading frame of the exon 6 is indicated in purple. (b) Gel electrophoresis and gel slice selection (dotted square) of chromatin fractions of SBRes used for trypsin digestion, tryptic peptides isolation and subsequent mass spectrometry analysis. (c) Targeted mass spectrometry SRM spectrum for the splice variant-specific peptide MDQADDVSCPLLNSCLSESGMWEFVSYTK detecting ten co-eluting fragment ions (color coded lines, left insert). A reconstituted spectrum using the SRM data is also shown (right insert). b ions (blue) and y ions (red) are annotated related to the peptide sequence