Fig. (3) Sec23a is ubiquitylated on cys432 and cys449. (A) Schematic representation of the Gly-Gly remnant left on ubiquitinated residues after trypsin digestion of the C-terminus of the linked ubiquitin (B;C) Output view of the software used for the search of the Gly-Gly modified peptides of Sec23a. The sequence and the MS/MS fragmentation peaks of the peptides containing the Gly-Gly-Cys 432 (B) and Gly-Gly-Cys 449 (C) are shown. (D) Extracted ion chromatograms corresponding to the Cys-modified peptide species.