Po is an alias for the gene, Proline-rich protein BstNI subfamily 4, in humans. Other names include: Basic salivary proline-rich protein 4; Parotid o protein; Salivary proline-rich protein II-1; Salivary proline-rich protein Po. The encoded protein has an amino acid length of 310 and a mass of 31.3 kDa. This gene shares homology with other species, including: Fly.