pDP4 is a secreted glycoprotein of the olfactomedin family. (A) Genetic locus of pDP4: The gene is expressed from 5 exons that span about 25 kb on mouse chromosome 14 (CELERA GA_x5J8B7W6JWY and NCBI accession NT_039606, gene LOC239192). Filled boxes symbolize the exons (E). (B) pDP4 is expressed as a peptide with an N-terminal signal peptide (SP) and a C-terminal olfactomedin-like domain (NCBI accession nos. XM_139161 and XP_139161 for the mRNA and peptide, respectively). The lower panel shows the peptide sequence comparison of the olfactomedin-like domains of mouse pDP4, human hGC-1/GW112, and bullfrog olfactomedin. Conserved amino acids are framed. The peptide used for generating the pDP4 antiserum is highlighted in the gray box. (C) Western blot using 60 μg of either total cell extracts or culture medium from mock or pcDNA-pDP4-HA-transfected COS-7 cells. Ngase F treatment of the culture medium extract demonstrates that pDP4 is secreted as a highly glycosylated protein. The membrane was hybridized with an antibody against the HA tag.