Proline Rich Protein 1, Lacrimal (PRL1)

BPLP is a putative 180-amino acid protein of 20.5 kD that contains a 21-residue secretory leader sequence, an N-glycosylation site, and a zona pellucida (Zp) domain. The Zp domain of BPLP shows most similarity to that of ZP2, which carries 2 insertions/deletions of identical size to those in BPLP. The BPLP protein consists of 24.5% proline, 10.5% leucine, and 8.4% each of arginine and serine residues. While the proline residues show 2 regions of clustering, BPLP shows no homology to the salivary proline-rich proteins. BPLP shows limited homology to human PRPb, the mouse MSG proteins, and rat VCS-alpha-1, VCS-beta-1, and submandibular apomucin. Northern blot analysis showed abundant expression of a 1.05-kb BPLP transcript in the lacrimal gland and moderate expression in the submandibular gland.