Figure 1

Functional domains of gp41 of HIV-1, location and alignment of the immunosuppressive (isu) domains of different retroviruses. FP, fusion peptide; FPPR, fusion peptide proximal region; NHR, N-terminal helical region; ISU, isu domain; S-S, cysteine-cysteine loop; CHR, C-terminal helical region; MPER, membrane proximal external region; MSD, membrane spanning domain. The location of the fusion inhibitor T20 (Enfuvirtide, Fuzeon) is shown as a black bar. Numbering on the top corresponds to the position according the accession number AF324493. The alignment of the conserved sequences of the isu domain of different retroviruses is given in the box (HIV-1, HIV-2, human immunodeficiency virus type −1, -2; SIVcpz, simian immunodeficiency virus of chimpanzees; HTLV-1, -2, human T-lymphotropic virus 1, 2; MPMV, Mason-Pfizer monkey virus; SRV-1, simian retrovirus 1; MuLV, murine leukemia virus; PERV, porcine endogenous retrovirus; syncytin 1 = human endogenous retrovirus HERV-W; syncytin 2 = human endogenous retrovirus HERV-FRD; HERV-K, human endogenous retrovirus-K). Residues common to group 1 and 2 are underlined. In brackets proteins (p) and glycoproteins (gp) and the molecular mass in kDa are indicated.