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HLA class II histocompatibility antigen, DP alpha 1 chain



Homo sapiens (Human)
Reviewed-Annotation score: -Experimental evidence at protein leveli


Binds peptides derived from antigens that access the endocytic route of antigen presenting cells (APC) and presents them on the cell surface for recognition by the CD4 T-cells. The peptide binding cleft accommodates peptides of 10-30 residues. The peptides presented by MHC class II molecules are generated mostly by degradation of proteins that access the endocytic route, where they are processed by lysosomal proteases and other hydrolases. Exogenous antigens that have been endocytosed by the APC are thus readily available for presentation via MHC II molecules, and for this reason this antigen presentation pathway is usually referred to as exogenous. As membrane proteins on their way to degradation in lysosomes as part of their normal turn-over are also contained in the endosomal/lysosomal compartments, exogenous antigens must compete with those derived from endogenous components. Autophagy is also a source of endogenous peptides, autophagosomes constitutively fuse with MHC class II loading compartments. In addition to APCs, other cells of the gastrointestinal tract, such as epithelial cells, express MHC class II molecules and CD74 and act as APCs, which is an unusual trait of the GI tract. To produce a MHC class II molecule that presents an antigen, three MHC class II molecules (heterodimers of an alpha and a beta chain) associate with a CD74 trimer in the ER to form a heterononamer. Soon after the entry of this complex into the endosomal/lysosomal system where antigen processing occurs, CD74 undergoes a sequential degradation by various proteases, including CTSS and CTSL, leaving a small fragment termed CLIP (class-II-associated invariant chain peptide). The removal of CLIP is facilitated by HLA-DM via direct binding to the alpha-beta-CLIP complex so that CLIP is released. HLA-DM stabilizes MHC class II molecules until primary high affinity antigenic peptides are bound. The MHC II molecule bound to a peptide is then transported to the cell membrane surface. In B-cells, the interaction between HLA-DM and MHC class II molecules is regulated by HLA-DO. Primary dendritic cells (DCs) also to express HLA-DO. Lysosomal microenvironment has been implicated in the regulation of antigen loading into MHC II molecules, increased acidification produces increased proteolysis and efficient peptide loading.

GO - Molecular functioni

  • MHC class II receptor activity Source: UniProtKB
  • peptide antigen binding Source: UniProtKB

GO - Biological processi

  • antigen processing and presentation of exogenous peptide antigen via MHC class II Source: UniProtKB
  • cellular response to interferon-gamma Source: UniProtKB
  • immune response Source: UniProtKB
  • interferon-gamma-mediated signaling pathway Source: Reactome
  • positive regulation of interferon-gamma production Source: UniProtKB
  • positive regulation of T cell activation Source: UniProtKB
  • positive regulation of T cell proliferation Source: UniProtKB
  • T cell receptor signaling pathway Source: Reactome


Biological processImmunity

Enzyme and pathway databases

ReactomeiR-HSA-202424 Downstream TCR signaling
R-HSA-202427 Phosphorylation of CD3 and TCR zeta chains
R-HSA-202430 Translocation of ZAP-70 to Immunological synapse
R-HSA-202433 Generation of second messenger molecules
R-HSA-2132295 MHC class II antigen presentation
R-HSA-389948 PD-1 signaling
R-HSA-877300 Interferon gamma signaling

Names & Taxonomyi

Protein namesi
Recommended name:
HLA class II histocompatibility antigen, DP alpha 1 chain
Alternative name(s):
HLA-SB alpha chain
MHC class II DP3-alpha
MHC class II DPA1
Gene namesi
Synonyms:HLA-DP1A, HLASB
OrganismiHomo sapiens (Human)
Taxonomic identifieri9606 [NCBI]
Taxonomic lineageiEukaryotaMetazoaChordataCraniataVertebrataEuteleostomiMammaliaEutheriaEuarchontogliresPrimatesHaplorrhiniCatarrhiniHominidaeHomo
  • UP000005640 Componenti: Chromosome 6

Organism-specific databases

MIMi142880 gene

Subcellular locationi

Extracellular region or secreted Cytosol Plasma membrane Cytoskeleton Lysosome Endosome Peroxisome ER Golgi apparatus Nucleus Mitochondrion Manual annotation Automatic computational assertionGraphics by Christian Stolte; Source: COMPARTMENTS


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Topological domaini29 – 222ExtracellularSequence analysisAdd BLAST194
Transmembranei223 – 245HelicalSequence analysisAdd BLAST23
Topological domaini246 – 260CytoplasmicSequence analysisAdd BLAST15

Keywords - Cellular componenti

Cell membrane, Endoplasmic reticulum, Endosome, Golgi apparatus, Lysosome, Membrane, MHC II

Pathology & Biotechi

Organism-specific databases


Polymorphism and mutation databases


PTM / Processingi

Molecule processing

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Signal peptidei1 – 28Add BLAST28
ChainiPRO_000001896729 – 260HLA class II histocompatibility antigen, DP alpha 1 chainAdd BLAST232

Amino acid modifications

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Glycosylationi109N-linked (GlcNAc...) asparagineSequence analysis1
Disulfide bondi138 ↔ 194PROSITE-ProRule annotation
Glycosylationi149N-linked (GlcNAc...) asparagine1 Publication1

Keywords - PTMi

Disulfide bond, Glycoprotein

Proteomic databases


PTM databases



Gene expression databases

ExpressionAtlasiP20036 baseline and differential
GenevisibleiP20036 HS

Organism-specific databases



Subunit structurei

Heterodimer of an alpha and a beta subunit; also referred as MHC class II molecule. In the endoplasmic reticulum (ER) it forms a heterononamer; 3 MHC class II molecules bind to a CD74 homotrimer (also known as invariant chain or HLA class II histocompatibility antigen gamma chain). In the endosomal/lysosomal system; CD74 undergoes sequential degradation by various proteases; leaving a small fragment termed CLIP on each MHC class II molecule. MHC class II molecule interacts with HLA_DM, and HLA_DO in B-cells, in order to release CLIP and facilitate the binding of antigenic peptides.

Protein-protein interaction databases

BioGridi109358, 101 interactors
IntActiP20036, 5 interactors


Secondary structure

Legend: HelixTurnBeta strandPDB Structure known for this area
Show more details
Feature keyPosition(s)DescriptionActionsGraphical viewLength
Beta strandi35 – 49Combined sources15
Beta strandi51 – 57Combined sources7
Beta strandi60 – 66Combined sources7
Turni67 – 70Combined sources4
Beta strandi71 – 76Combined sources6
Helixi77 – 82Combined sources6
Helixi87 – 107Combined sources21
Beta strandi119 – 126Combined sources8
Beta strandi134 – 146Combined sources13
Beta strandi149 – 154Combined sources6
Beta strandi157 – 159Combined sources3
Beta strandi161 – 165Combined sources5
Beta strandi176 – 184Combined sources9
Beta strandi191 – 197Combined sources7
Beta strandi201 – 203Combined sources3
Beta strandi205 – 210Combined sources6

3D structure databases


Miscellaneous databases


Family & Domainsi

Domains and Repeats

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Domaini118 – 210Ig-like C1-typeAdd BLAST93


Feature keyPosition(s)DescriptionActionsGraphical viewLength
Regioni29 – 115Alpha-1Add BLAST87
Regioni116 – 209Alpha-2Add BLAST94
Regioni210 – 222Connecting peptideAdd BLAST13

Sequence similaritiesi

Belongs to the MHC class II family.Curated

Keywords - Domaini

Signal, Transmembrane, Transmembrane helix

Phylogenomic databases

eggNOGiENOG410IZMF Eukaryota

Family and domain databases

Gene3Di2.60.40.10, 1 hit
3.10.320.10, 1 hit
InterProiView protein in InterPro
IPR007110 Ig-like_dom
IPR036179 Ig-like_dom_sf
IPR013783 Ig-like_fold
IPR003006 Ig/MHC_CS
IPR003597 Ig_C1-set
IPR011162 MHC_I/II-like_Ag-recog
IPR014745 MHC_II_a/b_N
IPR001003 MHC_II_a_N
PfamiView protein in Pfam
PF07654 C1-set, 1 hit
PF00993 MHC_II_alpha, 1 hit
SMARTiView protein in SMART
SM00407 IGc1, 1 hit
SM00920 MHC_II_alpha, 1 hit
SUPFAMiSSF48726 SSF48726, 1 hit
SSF54452 SSF54452, 1 hit
PROSITEiView protein in PROSITE
PS50835 IG_LIKE, 1 hit
PS00290 IG_MHC, 1 hit


Sequence statusi: Complete.

Sequence processingi: The displayed sequence is further processed into a mature form.

P20036-1 [UniParc]FASTAAdd to basket

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        10         20         30         40         50
60 70 80 90 100
110 120 130 140 150
160 170 180 190 200
210 220 230 240 250
Mass (Da):29,381
Last modified:February 1, 1991 - v1

Sequence cautioni

The sequence AAC64233 differs from that shown. Reason: Erroneous gene model prediction.Curated
The sequence AAD42927 differs from that shown. Reason: Erroneous gene model prediction.Curated

Experimental Info

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Sequence conflicti237I → F in CAA25143 (PubMed:6584734).Curated1


The following alleles of DPA1 are known: DPA1*01:03, DPA1*01:04, DPA1*01:05, DPA1*01:06, DPA1*01:07, DPA1*01:08, DPA1*01:09, DPA1*01:10, DPA1*02:01, DPA1*02:02, DPA1*02:03, DPA1*02:04, DPA1*03:01, DPA1*03:02, DPA1*03:03, DPA1*04:01 The sequence shown is that of DPA1*01:03.

Natural variant

Feature keyPosition(s)DescriptionActionsGraphical viewLength
Natural variantiVAR_05883242A → M in allele DPA1*02:02, allele DPA1*02:04, allele DPA1*03:01, allele DPA1*03:02 and allele DPA1*03:03; requires 2 nucleotide substitutions. Corresponds to variant dbSNP:rs386699859Ensembl.1
Natural variantiVAR_04768342A → T. Corresponds to variant dbSNP:rs1126533Ensembl.1
Natural variantiVAR_04768442A → V. Corresponds to variant dbSNP:rs1126534Ensembl.1
Natural variantiVAR_05883349P → T in allele DPA1*04:01. Corresponds to variant dbSNP:rs2308907Ensembl.1
Natural variantiVAR_05883454M → T in allele DPA1*01:09. Corresponds to variant dbSNP:rs1042175Ensembl.1
Natural variantiVAR_05883559E → D in allele DPA1*01:04, allele DPA1*01:08, allele DPA1*03:03 and allele DPA1*04:01. Corresponds to variant dbSNP:rs2308910Ensembl.1
Natural variantiVAR_05883662M → K. Corresponds to variant dbSNP:rs2308912Ensembl.1
Natural variantiVAR_04768562M → L. Corresponds to variant dbSNP:rs2308911Ensembl.1
Natural variantiVAR_05885062M → Q in allele DPA1*01:06, allele DPA1*02:01, allele DPA1*02:02 and allele DPA1*02:04; requires 2 nucleotide substitutions. Corresponds to variant dbSNP:rs36013091Ensembl.1
Natural variantiVAR_05883774W → C in allele DPA1*01:10. Corresponds to variant dbSNP:rs72558171Ensembl.1
Natural variantiVAR_04768681Q → R in allele DPA1*01:08, allele DPA1*02:01, allele DPA1*02:02, allele DPA1*02:03, allele DPA1*02:04 and allele DPA1*04:01. Corresponds to variant dbSNP:rs1042178Ensembl.1
Natural variantiVAR_05883882A → T in allele DPA1*01:07. Corresponds to variant dbSNP:rs41543112Ensembl.1
Natural variantiVAR_04768797L → S in allele DPA1*03:01 and allele DPA1*03:03. Corresponds to variant dbSNP:rs2308917Ensembl.1
Natural variantiVAR_058839100N → D in allele DPA1*02:04. Corresponds to variant dbSNP:rs61759929Ensembl.1
Natural variantiVAR_058840103T → I in allele DPA1*04:01. Corresponds to variant dbSNP:rs41559316Ensembl.1
Natural variantiVAR_058841104L → A in allele DPA1*04:01; requires 2 nucleotide substitutions. 1
Natural variantiVAR_047688114T → A in allele DPA1*01:05, allele DPA1*02:01, allele DPA1*02:02, allele DPA1*02:03, allele DPA1*02:04 and allele DPA1*04:01. Corresponds to variant dbSNP:rs1126542Ensembl.1
Natural variantiVAR_058842127P → A in allele DPA1*04:01. Corresponds to variant dbSNP:rs41562016Ensembl.1
Natural variantiVAR_047689142K → R in allele DPA1*02:01 and allele DPA1*02:02. Corresponds to variant dbSNP:rs1042190Ensembl.1
Natural variantiVAR_058843158L → P in allele DPA1*02:01, allele DPA1*02:02 and allele DPA1*04:01. Corresponds to variant dbSNP:rs2308930Ensembl.1
Natural variantiVAR_047690191F → V in allele DPA1*02:01, allele DPA1*02:02 and allele DPA1*04:01. Corresponds to variant dbSNP:rs1042308Ensembl.1
Natural variantiVAR_058844221T → A in allele DPA1*04:01. Corresponds to variant dbSNP:rs17509489Ensembl.1
Natural variantiVAR_058845259T → P in allele DPA1*02:01, allele DPA1*02:02 and allele DPA1*04:01. Corresponds to variant dbSNP:rs1126769Ensembl.1

Sequence databases

Select the link destinations:
Links Updated
X03100 Genomic DNA Translation: CAA26887.1
M27487 mRNA Translation: AAA63220.1
AK292709 mRNA Translation: BAF85398.1
AL645931 Genomic DNA No translation available.
AL805913 Genomic DNA No translation available.
BX120009 Genomic DNA No translation available.
BX005422 Genomic DNA No translation available.
CR759829 Genomic DNA No translation available.
CR759795 Genomic DNA No translation available.
CR847849 Genomic DNA No translation available.
CR759904 Genomic DNA No translation available.
CR762479 Genomic DNA No translation available.
CH471081 Genomic DNA Translation: EAX03669.1
X00457 mRNA Translation: CAA25143.1
Z48473 Genomic DNA No translation available.
AF013767 Genomic DNA Translation: AAC64233.1 Sequence problems.
X78199 Genomic DNA No translation available.
X82393 Genomic DNA No translation available.
X82394 Genomic DNA No translation available.
X78198 Genomic DNA No translation available.
X82391 Genomic DNA No translation available.
X79475 Genomic DNA No translation available.
X79477 Genomic DNA No translation available.
X79479 Genomic DNA No translation available.
X79481 Genomic DNA No translation available.
AF165160 Genomic DNA Translation: AAD47826.1
AY618553 Genomic DNA Translation: AAT92097.1
EU729350 Genomic DNA Translation: ACH88749.1
DQ274060 Genomic DNA Translation: ABB88406.1
DQ274061 Genomic DNA Translation: ABB88407.1
EU304462 Genomic DNA Translation: ABY27081.1
U87556 Genomic DNA Translation: AAB97110.1
AF346471 Genomic DNA Translation: AAK27152.1
AY650051 Genomic DNA Translation: AAT67468.1
AF076284 Genomic DNA Translation: AAD42927.1 Sequence problems.
X96984 Genomic DNA No translation available.
X80482 Genomic DNA No translation available.
X81347 Genomic DNA No translation available.
X81348 Genomic DNA No translation available.
K00514 Genomic DNA Translation: AAA59786.1
RefSeqiNP_001229453.1, NM_001242524.1
NP_001229454.1, NM_001242525.1
NP_291032.2, NM_033554.3

Genome annotation databases

EnsembliENST00000374808; ENSP00000363941; ENSG00000168384
ENST00000383224; ENSP00000372711; ENSG00000206291
ENST00000415247; ENSP00000405838; ENSG00000224103
ENST00000419277; ENSP00000393566; ENSG00000231389
ENST00000422504; ENSP00000406250; ENSG00000228163
ENST00000443117; ENSP00000397587; ENSG00000235844
ENST00000454805; ENSP00000397139; ENSG00000229685
ENST00000515317; ENSP00000427429; ENSG00000236177

Keywords - Coding sequence diversityi


Similar proteinsi

Entry informationi

Entry nameiDPA1_HUMAN
AccessioniPrimary (citable) accession number: P20036
Secondary accession number(s): A9YWH7
, B9UKH4, O19722, O46883, P01905, P79554, Q2Q060, Q2Q061, Q5EY03, Q5STP1, Q6DQK4, Q9BCQ1, Q9TPX3, Q9XS10
Entry historyiIntegrated into UniProtKB/Swiss-Prot: July 21, 1986
Last sequence update: February 1, 1991
Last modified: July 18, 2018
This is version 164 of the entry and version 1 of the sequence. See complete history.
Entry statusiReviewed (UniProtKB/Swiss-Prot)
Annotation programChordata Protein Annotation Program
DisclaimerAny medical or genetic information present in this entry is provided for research, educational and informational purposes only. It is not in any way intended to be used as a substitute for professional medical advice, diagnosis, treatment or care.


Keywords - Technical termi

3D-structure, Complete proteome, Reference proteome


  1. Human chromosome 6
    Human chromosome 6: entries, gene names and cross-references to MIM
  2. Human entries with polymorphisms or disease mutations
    List of human entries with polymorphisms or disease mutations
  3. Human polymorphisms and disease mutations
    Index of human polymorphisms and disease mutations
  4. MIM cross-references
    Online Mendelian Inheritance in Man (MIM) cross-references in UniProtKB/Swiss-Prot
  5. PDB cross-references
    Index of Protein Data Bank (PDB) cross-references
  6. SIMILARITY comments
    Index of protein domains and families

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