Figure 1.

Schematic representation of basic proline-rich genes and encoded proteins: PRB1 (A), PRB2 (B), PRB3 (C), PRB4 (D). For each protein, the genetic allelic variants (S, small; M, medium; L, large; and VL, very large) are shown on the left-sided column; the resulting alternative proteoforms are shown on the right-sided column as blocks, with the corresponding symbol on top. Vertical dashed lines indicate the pro-protein convertase cleavage sites with corresponding Arg (R) residues’ positions. The P enclosed in a circle denotes phosphorylation sites; aminoacidic substitutions are shown for selected isoforms. See text for additional details.