ID   ENV_FRSFL               Reviewed;         409 AA.
AC   P03394;
DT   21-JUL-1986, integrated into UniProtKB/Swiss-Prot.
DT   21-JUL-1986, sequence version 1.
DT   27-MAR-2024, entry version 116.
DE   RecName: Full=Glycoprotein 55;
DE            Short=gp55;
DE   Flags: Precursor;
GN   Name=env;
OS   Friend spleen focus-forming virus (strain Lilly-Steeves) (FSFFV).
OC   Viruses; Riboviria; Pararnavirae; Artverviricota; Revtraviricetes;
OC   Ortervirales; Retroviridae; Orthoretrovirinae; Gammaretrovirus;
OC   Spleen focus-forming virus.
OX   NCBI_TaxID=355328;
OH   NCBI_TaxID=10090; Mus musculus (Mouse).
RN   [1]
RP   NUCLEOTIDE SEQUENCE [GENOMIC DNA].
RX   PubMed=6308646; DOI=10.1073/pnas.80.15.4718;
RA   Wolff L., Scolnick E., Ruscetti S.;
RT   "Envelope gene of the Friend spleen focus-forming virus: deletion and
RT   insertions in 3' gp70/p15E-encoding region have resulted in unique features
RT   in the primary structure of its protein product.";
RL   Proc. Natl. Acad. Sci. U.S.A. 80:4718-4722(1983).
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       EPOR by gp55 causes uncontrolled, polyclonal proliferation of infected
CC       erythroblasts, leading to polycythemia (massive increase in the number
CC       of mature red cells). Host susceptibility to SSFV-induced
CC       erythroblastosis depends on the expression of the truncated isoform of
CC       MST1R receptor tyrosine kinase (MST1R isoform sf-Stk). Interaction with
CC       SSFV gp 55 results in constitutive tyrosine phosphorylation and
CC       activation of MST1R isoform sf-Stk (By similarity). {ECO:0000250}.
CC   -!- SUBUNIT: Homooligomer. Forms heterooligomers with mouse EPOR, probably
CC       via their respective transmembrane domains. Forms covalent heterodimers
CC       with mouse MST1R isoform sf-Stk, probably via disulfide bonds (By
CC       similarity). {ECO:0000250}.
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), gp55 corresponds to a gp70-p15E
CC       fusion protein with a deletion of a portion of p15E. It is encoded by
CC       the defective env gene of the virus.
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; V01552; CAA24793.1; -; Genomic_DNA.
DR   PIR; A03994; VCVW2S.
DR   SMR; P03394; -.
DR   GlyCosmos; P03394; 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; 1.10.287.210; -; 1.
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; 3.
DR   SUPFAM; SSF49830; ENV polyprotein, receptor-binding domain; 1.
PE   3: Inferred from homology;
KW   Disulfide bond; 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..409
FT                   /note="Glycoprotein 55"
FT                   /id="PRO_0000040720"
FT   TOPO_DOM        33..384
FT                   /note="Virion surface"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        385..405
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TOPO_DOM        406..409
FT                   /note="Intravirion"
FT                   /evidence="ECO:0000255"
FT   REGION          232..280
FT                   /note="Disordered"
FT                   /evidence="ECO:0000256|SAM:MobiDB-lite"
FT   COMPBIAS        249..276
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   409 AA;  44700 MW;  2D12505183293B3A CRC64;
     MEGPASSKPL KDKTNPWGPL IILGILIRAG VSVQLDSPHQ VSNVTWRVTN LMTGQTANAT
     SLLGTMTEAF PKLYFDLCDL MGDDWDETGL GCRTPGGRKR ARTFDFYVCP GHTVPTGCGG
     PREGYCGKWG CETTGQAYWK PSSSWDLISL KRGNTPKDQG PCYDSSVSSG VLGATPGGRC
     NPLVLEFTDA GRKASWDAPK VWGLRLYRST GTDPVTRFSL TRQVLDIGPR VPIGSNPVTT
     DQLPLSRPVQ TMPPRPLQPP PPGAASIVPE TAPPPQQPGA GDRLLNLVDG AYQALNLTNP
     DKIQECWLCL VSGPPYYEGV VVLGTYFNHT IALKEKCCFY ADHTGLVRDS MAKLRKRLTQ
     RQKLFESSRG WFEGSSNRSP WFTTLISAIM GSLIILLLLL ILLIWTLYS
//