Testis-Specific Proprotein Convertase 4: Gene Structure, Optional Exons, and mRNA Isoforms

Proprotein convertase 4 (PC4) is a member of the recently discovered family of eukaryotic serine endoproteinases characterized by their structural similarity to bacterial subtilisin and to the yeast Kex2 gene product, as well as by their cleavage specificity after pairs of basic residues (1–8). This family also includes furin, PC1/PC3, PC2, PACE4, and PC5/PC6. Unlike the other convertases that have wide, albeit distinct, tissue distributions (1–4, 7, 8), PC4 expression is restricted to testicular germ cells (5, 6, 10).