Sialophorin (SPN)

Sialophorin (leukosialin) is a major sialoglycoprotein on the surface of human T lymphocytes, monocytes, granulocytes, and some B lymphocytes, which appears to be important for immune function and may be part of a physiologic ligand-receptor complex involved in T-cell activation.The nucleotide sequence of the 1.7-kb clone showed that the sialophorin transcript has a 3-prime-noncoding region of 587 nucleotides, is polyadenylated, and has the AATAAA polyadenylation signal. The derived sequence of 341 amino acids showed that the sialophorin protein has 3 domains: an extracellular domain of 195 amino acids, a hydrophobic transmembrane domain of 23 amino acids, and a C-terminal intracellular domain of 123 amino acids which contains a number of sites that might be phosphorylated by protein kinase C.