IFITM family members contain a conservative CD225 domain and two terminal hypervariable regions [2] . The CD225 domain accounts for more than half of the protein in length, containing one intact transmembrane domain (TMD), two S-palmitoylation sites regions and partial TMD in the C-terminus of the protein. The S-palmitoylation sites have been demonstrated to play important roles in post-translational processing and stability of IFITM proteins [7] . The N-terminal hypervariable region generally contains 21 amino acid residues and the C-terminal one includes a TMD (Fig. 1) [8] .