ID   CD8A_PONPY              Reviewed;         198 AA.
AC   P30433;
DT   01-APR-1993, integrated into UniProtKB/Swiss-Prot.
DT   01-APR-1993, sequence version 1.
DT   25-MAY-2022, entry version 90.
DE   RecName: Full=T-cell surface glycoprotein CD8 alpha chain;
DE   AltName: Full=T-lymphocyte differentiation antigen T8/Leu-2;
DE   AltName: CD_antigen=CD8a;
DE   Flags: Precursor;
GN   Name=CD8A;
OS   Pongo pygmaeus (Bornean orangutan).
OC   Eukaryota; Metazoa; Chordata; Craniata; Vertebrata; Euteleostomi; Mammalia;
OC   Eutheria; Euarchontoglires; Primates; Haplorrhini; Catarrhini; Hominidae;
OC   Pongo.
OX   NCBI_TaxID=9600;
RN   [1]
RP   NUCLEOTIDE SEQUENCE [MRNA].
RC   STRAIN=Isolate Jari;
RX   PubMed=1612644; DOI=10.1007/bf00215289;
RA   Lawlor D.A., Parham P.;
RT   "Structure of CD8 alpha and beta chains of the orangutan: novel patterns of
RT   mRNA splicing encoding hingeless polypeptides.";
RL   Immunogenetics 36:121-125(1992).
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. LCK
CC       then initiates different intracellular signaling pathways by
CC       phosphorylating various substrates ultimately leading to lymphokine
CC       production, motility, adhesion and activation of cytotoxic T-
CC       lymphocytes (CTLs). This mechanism enables CTLs to recognize and
CC       eliminate infected cells and tumor cells. In NK-cells, the presence of
CC       CD8A homodimers at the cell surface provides a survival mechanism
CC       allowing conjugation and lysis of multiple target cells. CD8A homodimer
CC       molecules also promote the survival and differentiation of activated
CC       lymphocytes into memory CD8 T-cells. {ECO:0000250|UniProtKB:P01732}.
CC   -!- SUBUNIT: Forms disulfide-linked heterodimers with CD8B at the cell
CC       surface. Forms also homodimers in several cell types including NK-cells
CC       or peripheral blood T-lymphocytes. Interacts with the MHC class I HLA-
CC       A/B2M dimer. Interacts with LCK in a zinc-dependent manner.
CC       {ECO:0000250|UniProtKB:P01732}.
CC   -!- SUBCELLULAR LOCATION: Cell membrane {ECO:0000250|UniProtKB:P01732};
CC       Single-pass type I membrane protein {ECO:0000250|UniProtKB:P01732}.
CC       Note=CD8A localizes to lipid rafts only when associated with its
CC       partner CD8B. {ECO:0000250|UniProtKB:P01732}.
CC   -!- PTM: Palmitoylated, but association with CD8B seems to be more
CC       important for the enrichment of CD8A in lipid rafts.
CC       {ECO:0000250|UniProtKB:P01732}.
CC   -!- PTM: O-glycosylated. {ECO:0000250|UniProtKB:P01732}.
CC   -!- PTM: Phosphorylated in cytotoxic T-lymphocytes (CTLs) following
CC       activation. {ECO:0000250|UniProtKB:P01732}.
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DR   EMBL; X60223; CAA42784.1; -; mRNA.
DR   PIR; S25656; S25656.
DR   AlphaFoldDB; P30433; -.
DR   SMR; P30433; -.
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:0002250; P:adaptive immune response; IEA:UniProtKB-KW.
DR   Gene3D; 2.60.40.10; -; 1.
DR   InterPro; IPR015468; CD8_asu.
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; PTHR10441; PTHR10441; 2.
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:0000250"
FT   CHAIN           22..198
FT                   /note="T-cell surface glycoprotein CD8 alpha chain"
FT                   /id="PRO_0000014640"
FT   TOPO_DOM        22..145
FT                   /note="Extracellular"
FT                   /evidence="ECO:0000255"
FT   TRANSMEM        146..166
FT                   /note="Helical"
FT                   /evidence="ECO:0000255"
FT   TOPO_DOM        167..198
FT                   /note="Cytoplasmic"
FT                   /evidence="ECO:0000255"
FT   DOMAIN          22..135
FT                   /note="Ig-like V-type"
FT   LIPID           169
FT                   /note="S-palmitoyl cysteine"
FT                   /evidence="ECO:0000250|UniProtKB:P01732"
FT   DISULFID        43..115
FT                   /evidence="ECO:0000255|PROSITE-ProRule:PRU00114"
SQ   SEQUENCE   198 AA;  22099 MW;  F3EC093EADB05561 CRC64;
     MALPVTALLL PLALLLHAAR PSQFRVSPLD RTWNLGETVE LKCQVLLSNP TSGCSWLFQP
     RGAAASPTFL LYLSQNKPKA AEGLDTQRFS GKRLGDTFVL TLSDFRRENE GYYFCSALSN
     SIMYFSHFVP VFLPVHTRGL DFACDIYIWA PLAGTCGVLL LSLVITLYCN HRNRRRVCKC
     PRPVVKSGGK PSLSERYV