Figure 6.

MLV Env protein. MLV Env protein consists of a complex between gp70^SU and p15E^TM. The cartoon shows that gp70 has two domains, RBD at its N-terminus and “C-term” at its C-terminus, separated by a variable, proline-rich linker. P15E contains, from N- to C-terminus, the fusion peptide (FP), an N-terminal helical domain (helix A), a short C-terminal helical domain (helix B), and a C-terminal domain (light pink) which spans the viral membrane (yellow). Gp70 is exclusively external to the virus and is connected to p15E by a disulfide linkage between one of the two cysteines in a CXXC motif within its C-terminal domain and the last cysteine in a CX₆CC motif in p15E.