This document summarizes key structural and functional properties of rat CD4 protein as reported in three scientific publications. It describes the crystal structure of the CD4 protein domains 3 and 4 determined in 1993 and locations of N-linked glycosylation sites, serine phosphorylation site involved in Lck dissociation, and cysteine residues important for Lck binding and palmitoylation. A 2003 study is also cited that examined the role of palmitoylation in CD4 lipid raft association.