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. Author manuscript; available in PMC: 2015 Jan 15.
Published in final edited form as: Annu Rev Virol. 2014 Nov 1;1:261–283. doi: 10.1146/annurev-virology-031413-085537

Figure 2.

Figure 2

The topological domains of the IFITM proteins are shown above an alignment of immunity-related IFITM proteins of humans (h), mice (m), chickens (c), and rainbow trout (fish; f). Domains consist of the N-terminal domain (NTD), intramembrane domain (IMD), conserved intracellular loop (CIL), transmembrane domain (TMD), and C-terminal domain (CTD). The junction of the TMD and CTD is poorly defined. Residues are numbered according to human IFITM3, and where applicable, highlighting of important amino acids has been extended to include orthologous residues in other species. The NTD is poorly conserved, but the NTDs of human IFITM2 and IFITM3 and their orthologs all contain YXXF motifs (green) that promote their internalization into endolysosomes (68). Phosphorylation of Tyr20 by Fyn kinase inhibits this internalization (59). Ubiquitylation of Lys24 in human IFITM3 (blue) promotes its degradation (49). Palmitoylated cysteines (orange) are required for proper subcellular localization and restriction of viral entry (49). Two phenylalanines (gray) in the IMD have been proposed to promote dimerization (41). Methylation of Lys88 (purple) negatively regulates restriction activity (63).