Schematic illustration of the mammalian Gag and Env expression constructs. (A) Schematic outline of the PFV Gag precursor protein. Structural and functional domains are indicated in differentially shaded boxes as explained below. The major processing site in p71Gag is marked by a solid arrow and potential secondary cleavage sites by dashed arrows. Numbers indicate amino acid positions in PFV Gag. (B) Schematic outline of the PFV Gag expression constructs. All constructs harbor a C-terminal flexible (Gly4Ser1)3 linker (L) and either a HA-6xHis-tag (HH) or EGFP-HA-6xHis-tag (EGFP-HH) indicated as white boxes. (C) Schematic outline of the PFV Env expression constructs. On top the outline of the wild type full-length PFV Env coding sequences are show as grey boxes with different hydrophobic sequence indicated as black boxes as explained below. The major processing sites in gp130Env are marked by solid arrows. Numbers indicate amino acid positions in PFV Env. Below an outline of the individual Env expression constructs is shown. All constructs harbor a C-terminal flexible (Gly4Ser1)3 linker (L) and GST-tag. W denotes the conserved tryptophan residues at position 10 and 13 of the PFV Env ORF. CC: coiled-coil motif; CTRS: cytoplasmic targeting and retention signal; L: PSAP late-assembly (L)-domain motif; A: YXXLGL assembly domain motif; GR: glycine-arginine rich box; h: hydrophobic domain of the leader peptide (LP); FP: fusion peptide of the transmembrane subunit (TM); MSD: membrane-spanning domain of the TM subunit; SU: surface subunit; Y: N-glycosylation sites.