Figure 2.

Principal acidic proline-rich protein (aPRP) proteoforms: in blue are the entire proteoforms and in red are the truncated ones. Red arrows indicate the cleavage site recognized by convertase activity, from which PRP-3-type truncated forms and the P-C peptide are generated from the entire PRP-1-type forms. Grey arrows indicate the possible loss of C-terminal residue by carboxypeptidase activity. Pyroglutamination N-terminal is evidenced in yellow, while the Ser residues that can undergo phosphorylation are evidenced in light green. The different phosphorylated proteoforms obtainable from the entire and truncated aPRPs are shown, as well as the disulfide dimeric form of Pa.