Fig. 2.

Identification of C-terminal proteolytic processing events in CCP1-transfected cells by means of C-terminal COFRADIC analysis. A, Representation of a protein that is not processed by CCP1. Scissors indicate trypsin cleavage sites. N-terminal tryptic peptides are colored in red. C-terminal tryptic peptides are colored in green/blue. Internal tryptic peptides are colored in yellow. B, Representation of a protein that is C-terminally processed by CCP1. C, Mass spectrum representation of a C-terminal peptide that is not processed in both proteomes (Peptide A). This mass spectrum would equally represent a C-terminal peptide showing basal degradation in both proteomes by a protease different from CCP1. D, Mass spectrum representation of the intact C-terminal peptide of a protein that is processed by CCP1 (Peptide B). E, Mass spectrum representation of the neo-C-terminal peptide of a protein that is processed by CCP1 (Peptide C). F, Identification of α-tubulin 1A/1B as CCP1 substrate. Mass spectrum of the triply charged neo-C terminus of α-tubulin 1A/1B, But¹³C₄-EDMAALEKDYEEVGVDSVEGEGEEEG (residues 423–448; But¹³C₄, α-amino group modified by ¹³C₄-butyric acid).