FIG. 1.

Schematic diagram of the wild-type F-MuLV Env protein and cytoplasmic tail insertion mutants. Construction of the plasmids containing the insertion mutations is described in Materials and Methods. The designation of each Env protein is given on the left. Shaded box, TM domain. The amino acid sequence of the cytoplasmic tail is shown, and the R peptide-coding region is underlined. The inserted and substituted amino acids are in boldface italics. (A) The full-length 32-amino-acid sequence of the F-MuLV Env protein (Menv) and the sequence of the R peptide-truncated Env protein (MenvR-) are shown. Mutants with insertions after residue F614 are shown below. (B) Mutants with insertions after I619 and the substitution at I619 are aligned at the transmembrane and cytoplasmic domains with other F-MuLV Env proteins.