Glycoprotein A33 (GPA33) is also known as Cell surface A33 antigen, is a single-pass type I membrane protein which is expressed in normal gastrointestinal epithelium and in 95% of colon cancers. GPA33 The predicted mature protein has a 213-amino acid extracellular region, a single transmembrane domain, and a 62-amino acid intracellular tail. The sequence of the extracellular region contains 1 Ig-like C2-type (immunoglobulin-like) domain and 1 Ig-like V-type (immunoglobulin-like) domain characteristic of the CD2 subgroup of the immunoglobulin (Ig) superfamily, which contains. GPA33 may play a role in cell-cell recognition and signaling.