CHARACTERIZATION OF A BOVINE MAMMARY-GLAND PP3 CDNA REVEALS HOMOLOGY WITH MOUSE AND RAT ADHESION MOLECULE GLYCAM-1

full length PP3 (Proteose;Peptone component 3) cDNA of 679 bp was isol ated from a bovine mammary gland cDNA library. The cDNA encodes a sign al peptide of 18 amino acids followed by the mature PP3 sequence of 13 5 amino acids. This polypeptide showed homology with mouse and rat Gly CAM-1 (Glycosylation dependent Cell Adhesion Molecule I) a protein whi ch has been shown to act as a ligand for lymphocytes. The similarity w as most profound between the signal peptides and three short regions o f the mature polypeptides. Additionally structural conservation was pr edicted by computer analysis in the shape of a C-terminal amphipathic helix. PP3 was found to be expressed in mammary gland but not in perip heral lymph nodes, Peyer's pathes, lung, spleen, heart, and muscle.