SMAGP (small transmembrane and glycosylated protein) is a 25 kD, type III transmembrane glycoprotein that participates in epithelial cell polarity. Rat SMAGP is 97 amino acids (aa) in length and contains no signal sequence. The N-terminal 34 amino acids constitute the extracellular domain and show O-linked glycosylation. The C-terminal 42 amino acids (# 56-97) make up the cytoplasmic region. SMAGP is likely involved in cell adhesion and communication. Relocation of SMAGP from the membrane to the cytosol is associated with tissue disorganization and metastatic transformation. Over the extracellular and cytoplasmic domains, rat SMAGP shares 96% and 66% aa sequence identity with mouse and human SMAGP, respectively.