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MGP001491

UniProt Annotations

Entry Information
Gene Namehaptoglobin
Protein EntryHPT_HUMAN
UniProt IDP00738
SpeciesHuman
Comments
Comment typeDescription
Alternative ProductsEvent=Alternative splicing; Named isoforms=2; Name=1; IsoId=P00738-1; Sequence=Displayed; Name=2; IsoId=P00738-2; Sequence=VSP_055024; Note=No experimental confirmation available. Gene prediction based on EST data.;
CautionAlthough homologous to serine proteases, it has lost all essential catalytic residues and has no enzymatic activity. {ECO:0000305}.
DiseaseAnhaptoglobinemia (AHP) [MIM:614081]: A condition characterized by the absence of the serum glycoprotein haptoglobin. Serum levels of haptoglobin vary among normal persons: levels are low in the neonatal period and in the elderly, differ by population, and can be influenced by environmental factors, such as infection. Secondary hypohaptoglobinemia can occur as a consequence of hemolysis, during which haptoglobin binds to free hemoglobin. Congenital haptoglobin deficiency is a risk factor for anaphylactic non-hemolytic transfusion reactions. {ECO:0000269|PubMed:14999562}. Note=The disease is caused by mutations affecting the gene represented in this entry.
FunctionAs a result of hemolysis, hemoglobin is found to accumulate in the kidney and is secreted in the urine. Haptoglobin captures, and combines with free plasma hemoglobin to allow hepatic recycling of heme iron and to prevent kidney damage. Haptoglobin also acts as an Antimicrobial; Antioxidant, has antibacterial activity and plays a role in modulating many aspects of the acute phase response. Hemoglobin/haptoglobin complexes are rapidely cleared by the macrophage CD163 scavenger receptor expressed on the surface of liver Kupfer cells through an endocytic lysosomal degradation pathway. {ECO:0000269|PubMed:21248165}.
FunctionUncleaved haptoglogin, also known as zonulin, plays a role in intestinal permeability, allowing intercellular tight junction disassembly, and controlling the equilibrium between tolerance and immunity to non-self antigens. {ECO:0000269|PubMed:21248165}.
InteractionP02647:APOA1; NbExp=3; IntAct=EBI-1220767, EBI-701692; P02649:APOE; NbExp=7; IntAct=EBI-1220767, EBI-1222467;
PolymorphismIn the human populations there are two major allelic forms, alpha-1 (1-1) with 83 residues and alpha-2 (2-2) with 142 residues. These alleles determine 3 possible genotypes, homozygous (1-1 or 2-2) and heterozygous (2-1), and 3 major phenotypes HP*1F/HP*1S and HP*2FS. The two main alleles of HP*1 are called HP*1F (fast) and HP*1S (slow). The alleles exhibit different oligomerization properties. In healthy males, but not in females, the Hp 2-2 phenotype is associated with higher serum iron, decreased Antimicrobial; Antioxidant capability, and less efficient clearance from the circulation, than Hp 1-1 and 2-1.
SimilarityBelongs to the peptidase S1 family. {ECO:0000255|PROSITE-ProRule:PRU00274}.
SimilarityContains 1 peptidase S1 domain. {ECO:0000255|PROSITE- ProRule:PRU00274}.
SimilarityContains 2 Sushi (CCP/SCR) domains. {ECO:0000255|PROSITE-ProRule:PRU00302}.
Subcellular LocationSecreted.
SubunitTetramer of two alpha and two beta chains; disufide- linked. The Hemoglobin/haptoglobin complex is composed of a haptoglobin dimer bound to two hemoglobin alpha-beta dimers. Interacts with CD163.
Tissue SpecificityExpressed by the liver and secreted in plasma.
Web ResourceName=SHMPD; Note=The Singapore human mutation and polymorphism database; URL="http://shmpd.bii.a-star.edu.sg/gene.php?genestart=A&genename=HP";
Web ResourceName=Wikipedia; Note=Haptoglobin entry; URL="http://en.wikipedia.org/wiki/Haptoglobin";
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