ID   ENV_FRSFB               Reviewed;         356 AA.
AC   P31793;
DT   01-JUL-1993, integrated into UniProtKB/Swiss-Prot.
DT   01-JUL-1993, sequence version 1.
DT   27-MAR-2024, entry version 106.
DE   RecName: Full=Glycoprotein 42;
DE            Short=gp42;
DE   Flags: Precursor;
GN   Name=env;
OS   Friend spleen focus-forming virus (strain BB6) (FSFFV).
OC   Viruses; Riboviria; Pararnavirae; Artverviricota; Revtraviricetes;
OC   Ortervirales; Retroviridae; Orthoretrovirinae; Gammaretrovirus;
OC   Spleen focus-forming virus.
OX   NCBI_TaxID=31692;
OH   NCBI_TaxID=10090; Mus musculus (Mouse).
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=1583724; DOI=10.1128/jvi.66.6.3652-3660.1992;
RA   Majumdar M.K., Cho C.L., Fox M.T., Eckner K.L., Kozak S., Kabat D.,
RA   Geib R.W.;
RT   "Mutations in the env gene of friend spleen focus-forming virus overcome
RT   Fv-2r-mediated resistance to Friend virus-induced erythroleukemia.";
RL   J. Virol. 66:3652-3660(1992).
CC   -!- FUNCTION: This envelope-like membrane glycoprotein is responsible for
CC       ligand-independent activation of the erythropoietin receptor EPOR
CC       leading to the abnormally rapid proliferation of erythroid precursor
CC       cells. In the first stage of Friend disease, constitutive activation of
CC       the EPOR by gp42 causes uncontrolled, polyclonal proliferation of
CC       infected erythroblasts, leading to polycythemia (massive increase in
CC       the number of mature red cells). Host susceptibility to SSFV-induced
CC       erythroblastosis usually depends on the expression of the truncated
CC       isoform of MST1R receptor tyrosine kinase (MST1R isoform sf-Stk), but
CC       the deletion mutant BB6 apparently can overcome its absence.
CC   -!- SUBUNIT: Homooligomer. Forms heterooligomers with mouse EPOR, probably
CC       via their respective transmembrane domains. BB6 deletion mutant does
CC       not interact with mouse MST1R isoform sf-Stk.
CC   -!- SUBCELLULAR LOCATION: Host endoplasmic reticulum membrane; Single-pass
CC       type I membrane protein. Host cell membrane; Single-pass type I
CC       membrane protein. Virion membrane; Single-pass type I membrane protein.
CC       Note=The envelope-like membrane glycoprotein gp55 is defective in its
CC       transport to the cell surface and remains associated predominantly with
CC       the rough endoplasmic reticulum (RER) membrane. It is almost not
CC       incorporated into virions. Host cell surface expression appears to be a
CC       prerequisite for its leukemogenicity (By similarity). {ECO:0000250}.
CC   -!- MISCELLANEOUS: Compared to other gammaretroviruses which possess 2
CC       envelope proteins (gp70 and p15E), FSFFV gp55 corresponds to a gp70-
CC       p15E fusion protein with a deletion of a portion of p15E. It is encoded
CC       by the defective env gene of the virus. Strain BB6 gp42 is a truncated
CC       form of gp55.
CC   -!- MISCELLANEOUS: The Friend murine leukemia virus complex induces a rapid
CC       and fatal erythroleukemia in adult mice. It is the replication-
CC       defective spleen focus-forming virus (SFFV) contained in this complex
CC       that causes foci of proliferating erythroid cells in spleens of
CC       infected mice. The second component is a replication competent Friend
CC       murine leukemia virus (F-MuLV) that serves as a helper virus for SFFV.
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DR   EMBL; M90673; -; NOT_ANNOTATED_CDS; Genomic_DNA.
DR   PIR; A41995; VCVWB6.
DR   SMR; P31793; -.
DR   GlyCosmos; P31793; 4 sites, No reported glycans.
DR   GO; GO:0044167; C:host cell endoplasmic reticulum membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0020002; C:host cell plasma membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0016020; C:membrane; IEA:UniProtKB-KW.
DR   GO; GO:0019031; C:viral envelope; IEA:UniProtKB-KW.
DR   GO; GO:0055036; C:virion membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0019064; P:fusion of virus membrane with host plasma membrane; IEA:UniProtKB-KW.
DR   GO; GO:0046718; P:viral entry into host cell; IEA:UniProtKB-KW.
DR   GO; GO:0019062; P:virion attachment to host cell; IEA:UniProtKB-KW.
DR   Gene3D; 3.90.310.10; ENV polyprotein, receptor-binding domain; 1.
DR   InterPro; IPR008981; FMuLV_rcpt-bd.
DR   InterPro; IPR018154; TLV/ENV_coat_polyprotein.
DR   PANTHER; PTHR10424:SF77; BC035947 PROTEIN-RELATED; 1.
DR   PANTHER; PTHR10424; VIRAL ENVELOPE PROTEIN; 1.
DR   Pfam; PF00429; TLV_coat; 2.
DR   SUPFAM; SSF49830; ENV polyprotein, receptor-binding domain; 1.
PE   3: Inferred from homology;
KW   Fusion of virus membrane with host cell membrane;
KW   Fusion of virus membrane with host membrane; Glycoprotein;
KW   Host cell membrane; Host endoplasmic reticulum; Host membrane;
KW   Host-virus interaction; Membrane; Oncogene; Signal; Transmembrane;
KW   Transmembrane helix; Viral attachment to host cell; Viral envelope protein;
KW   Viral penetration into host cytoplasm; Virion; Virus entry into host cell.
FT   SIGNAL          1..32
FT                   /evidence="ECO:0000255"
FT   CHAIN           33..356
FT                   /note="Glycoprotein 42"
FT                   /id="PRO_0000040722"
FT   TOPO_DOM        33..331
FT                   /note="Virion surface"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        332..352
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TOPO_DOM        353..356
FT                   /note="Intravirion"
FT                   /evidence="ECO:0000255"
FT   REGION          247..279
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   MOTIF           306..309
FT                   /note="CXXC"
FT   COMPBIAS        249..268
FT                   /note="Pro residues"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   CARBOHYD        43
FT                   /note="N-linked (GlcNAc...) asparagine; by host"
FT                   /evidence="ECO:0000255"
FT   CARBOHYD        58
FT                   /note="N-linked (GlcNAc...) asparagine; by host"
FT                   /evidence="ECO:0000255"
FT   CARBOHYD        296
FT                   /note="N-linked (GlcNAc...) asparagine; by host"
FT                   /evidence="ECO:0000255"
FT   CARBOHYD        328
FT                   /note="N-linked (GlcNAc...) asparagine; by host"
FT                   /evidence="ECO:0000255"
SQ   SEQUENCE   356 AA;  38778 MW;  0C7893BE2794F980 CRC64;
     MEGPAFSKPL KDKINPWGPL IVLGILIRAG VSVQRDSPHQ VFNVTWRVTN LMTGQTANAT
     SLLGTMTDAF PKLYFDLCDL IGNDWDETRL GCRTPGEGKR ARTFDLYVCP GHTVPTGCGG
     PREGYCGKWG CETTGQAYWK PSSSWDLISL KRGNTPKDRG PCYDSSVSSG VQGATPGGRC
     NPLVLKFTDA GKKASWDAPK VWGLRLYRST GTDPVTRFSL TRQVLNIGPR VPIGPNPVIS
     DQLPPSRPAQ IMLPRPPQPP PPGTASIVPE TAPPSQQPGT RDRLLNLVNK AYQALNLTSP
     DKTQECWLCL VSRPPYYEGV AVLGTNSNHT TLISTIMGLL IILLLLLILL LWTLHS
//