ID   CD8B_SAISC              Reviewed;         209 AA.
AC   Q9XSM7;
DT   24-JAN-2001, integrated into UniProtKB/Swiss-Prot.
DT   01-NOV-1999, sequence version 1.
DT   25-MAY-2022, entry version 88.
DE   RecName: Full=T-cell surface glycoprotein CD8 beta chain;
DE   AltName: CD_antigen=CD8b;
DE   Flags: Precursor;
GN   Name=CD8B; Synonyms=CD8B1;
OS   Saimiri sciureus (Common squirrel monkey).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia;
OC   Eutheria; Euarchontoglires; Primates; Haplorrhini; Platyrrhini; Cebidae;
OC   Saimiriinae; Saimiri.
OX   NCBI_TaxID=9521;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   STRAIN=Isolate 92039;
RX   PubMed=10369934; DOI=10.1007/s002510050672;
RA   Ureta-Vidal A., Garcia Z., Lemonnier F.A., Kazanji M.;
RT   "Molecular characterization of cDNAs encoding squirrel monkey (Saimiri
RT   sciureus) CD8 alpha and beta chains.";
RL   Immunogenetics 49:718-721(1999).
CC   -!- FUNCTION: Integral membrane glycoprotein that plays an essential role
CC       in the immune response and serves multiple functions in responses
CC       against both external and internal offenses. In T-cells, functions
CC       primarily as a coreceptor for MHC class I molecule:peptide complex. The
CC       antigens presented by class I peptides are derived from cytosolic
CC       proteins while class II derived from extracellular proteins. Interacts
CC       simultaneously with the T-cell receptor (TCR) and the MHC class I
CC       proteins presented by antigen presenting cells (APCs). In turn,
CC       recruits the Src kinase LCK to the vicinity of the TCR-CD3 complex. A
CC       palmitoylation site in the cytoplasmic tail of CD8B chain contributes
CC       to partitioning of CD8 into the plasma membrane lipid rafts where
CC       signaling proteins are enriched. Once LCK recruited, it initiates
CC       different intracellular signaling pathways by phosphorylating various
CC       substrates ultimately leading to lymphokine production, motility,
CC       adhesion and activation of cytotoxic T-lymphocytes (CTLs).
CC       Additionally, plays a critical role in thymic selection of CD8+ T-
CC       cells. {ECO:0000250|UniProtKB:P10300, ECO:0000250|UniProtKB:P10966}.
CC   -!- SUBUNIT: Forms disulfide-linked heterodimers with CD8A at the cell
CC       surface. Interacts with CD3D; this interaction couples TCR-CD3 with
CC       CD8. Interacts with LCK. {ECO:0000250|UniProtKB:P10300,
CC       ECO:0000250|UniProtKB:P10966}.
CC   -!- SUBCELLULAR LOCATION: Cell membrane {ECO:0000250|UniProtKB:P10966};
CC       Single-pass type I membrane protein {ECO:0000250|UniProtKB:P10966}.
CC       Note=Requires the partner CD8A for efficient cell surface expression.
CC       The heterodimer CD8A/CD8B localizes to lipid rafts due to CD8B
CC       cytoplasmic tail palmitoylation. {ECO:0000250|UniProtKB:P10966}.
CC   -!- PTM: Phosphorylated as a consequence of T-cell activation.
CC       {ECO:0000250|UniProtKB:P10966}.
CC   -!- PTM: Palmitoylated at the cytoplasmic tail and thereby targets the
CC       heterodimer CD8A/CD8B to lipid rafts unlike CD8A homodimers.
CC       {ECO:0000250|UniProtKB:P10966}.
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DR   EMBL; AJ130819; CAB41463.1; -; mRNA.
DR   AlphaFoldDB; Q9XSM7; -.
DR   SMR; Q9XSM7; -.
DR   GO; GO:0016021; C:integral component of membrane; IEA:UniProtKB-KW.
DR   GO; GO:0005886; C:plasma membrane; IEA:UniProtKB-SubCell.
DR   GO; GO:0015026; F:coreceptor activity; IEA:InterPro.
DR   GO; GO:0042288; F:MHC class I protein binding; IEA:InterPro.
DR   GO; GO:0002250; P:adaptive immune response; IEA:UniProtKB-KW.
DR   GO; GO:0050776; P:regulation of immune response; IEA:InterPro.
DR   Gene3D; 2.60.40.10; -; 1.
DR   InterPro; IPR042414; CD8B.
DR   InterPro; IPR007110; Ig-like_dom.
DR   InterPro; IPR036179; Ig-like_dom_sf.
DR   InterPro; IPR013783; Ig-like_fold.
DR   InterPro; IPR003599; Ig_sub.
DR   InterPro; IPR013106; Ig_V-set.
DR   PANTHER; PTHR11292; PTHR11292; 1.
DR   Pfam; PF07686; V-set; 1.
DR   SMART; SM00409; IG; 1.
DR   SMART; SM00406; IGv; 1.
DR   SUPFAM; SSF48726; SSF48726; 1.
DR   PROSITE; PS50835; IG_LIKE; 1.
PE   2: Evidence at transcript level;
KW   Adaptive immunity; Cell membrane; Disulfide bond; Glycoprotein; Immunity;
KW   Immunoglobulin domain; Lipoprotein; Membrane; Palmitate; Signal;
KW   Transmembrane; Transmembrane helix.
FT   SIGNAL          1..21
FT                   /evidence="ECO:0000255"
FT   CHAIN           22..209
FT                   /note="T-cell surface glycoprotein CD8 beta chain"
FT                   /id="PRO_0000014647"
FT   TOPO_DOM        22..169
FT                   /note="Extracellular"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        170..190
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TOPO_DOM        191..209
FT                   /note="Cytoplasmic"
FT                   /evidence="ECO:0000255"
FT   DOMAIN          22..131
FT                   /note="Ig-like V-type"
FT   CARBOHYD        101
FT                   /note="N-linked (GlcNAc...) asparagine"
FT                   /evidence="ECO:0000255"
FT   DISULFID        41..115
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00114"
SQ   SEQUENCE   209 AA;  23481 MW;  E595E8E39DF629C5 CRC64;
     MRPRMWLLLS AQLAALHGNS VLQQTPAYIM VQTNQMVMLS CKAISSSTTR IYWLRQLHAP
     SSNSHHEILA FWDSSKGTIH SEGVEQKKIT VFRDGSLFFL NLTRVKLEDS GTYFCMVIGS
     PTLIFGTGTQ LSVVDILPTT AQTTKKSTPK KTVCRLPRPE TRKGPLCSPI TLSLLVAGIL
     VLLVSLGVAI HLYCRQRRAR LRFMKQFYK