Figure 5.

Conservation of CXXC, ISD and CX₆CC motifs of gamma-type Envs. Geneious amino acid alignment of 27 gammaretroviral and gamma-like Env sequences and the CKS-17 peptide. Endogenous sequences are shown in red while exogenous viruses are shown in black. On the left is a section from SU containing the CXXC motif (which is absent from alpharetroviral and filoviral entry proteins). The CXXC contributes to an intersubunit disulfide bond with the third cysteine in the CX₆CC motif in TM. On the right is a section of sequence from TM that contains the highly conserved region of the immunosuppressive domain (ISD). The CKS-17 peptide was used to originally define the region of the ISD; also highlighted is the intra-subunit bond that forms within the CX₆CC motif. RSV and ALV are classified as alpharetroviruses, SRV3 is a betaretrovirus with a gamma-like Env, and HTLV is a deltaretrovirus; also notable is the gamma-like glycoprotein of Ebola virus which is a member of Filoviridae. Accession #s in order of figure: AFV99542.1; BAD98245.1; Q05320.1; ACI62863.1; AGI61275.1; P07575.1; ABS71857.1; QXV86750.1; P31796.1; NP_041262.1; NP_001291475.1; Q9UQF0.1; XP_022270294.1; AAM34209.1; XP_040289417.1; XP_025743503.1; QXP50143.1; XP_015345157.1; AAAU04934.1; AYG96595.1; ACD35952.1; AAQ88184.1; P26804.1; AEI59727.1; ALX81658.1; ALV83307.1; AAB03092.1.