Figure 6

Relationship between Xq22.3 HERV-W Env, MSRV Env, and Syncytin-1. An amino acid sequence alignment of Xq22.3 HERV-W Env, MSRV Env (clones AF127228 and AF331500), and Syncytin-1 is shown. The sequence of a HERV-W element on chromosome 5p12 from which the C-terminal region of the MSRV env clone AF331500 is derived (see also Table 3 and Additional file 2) is also shown. For the sake of simplicity, only the C-terminal region of the 5p12 element is included. The region of MSRV Env (AF331500) originating from HERV-W 5p12 is highlighted in yellow. Predicted signal peptides (according to SignalP 3.0, http://www.cbs.dtu.dk/services/SignalP/) are shaded in gray. The stop codon at position 39 of Xq22.3 HERV-W Env and AF127228 is indicated by a dot (·). The consensus C-X-X-C motif conserved among C-type and D-type retroviral Env proteins [42] is shown in boldface. The border between the SU and TM regions is indicated by arrows. The proteolytic cleavage site (consensus R/K-X-R/K-R) between SU and TM is highlighted in red letters. The sequences of the MSRV Env SU protein (generated using the MSRV env clone AF331500) studied by Rolland et al. [24] is marked in red. The fragment of the MSRV env clone AF127228 used for generation of the anti HERV-W Env monoclonal antibody 6A2B2 [16] is shown in green.