HLA-DRB1
Encyclopedia
HLA class II histocompatibility antigen, DRB1-9 beta chain is a protein
that in humans is encoded by the HLA-DRB1 gene
. DRB1 encodes the most prevalent beta subunit of HLA-DR.
encoded by this gene belongs to the HLA class II
beta chain paralogues. The class II molecule is a heterodimer consisting of an alpha (DRA) and a beta chain (DRB), both anchored in the membrane. It plays a central role in the immune system
by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages).
s, exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular domains
, exon 4 encodes the transmembrane
domain and exon 5 encodes the cytoplasm
ic tail. Within the DR molecule the beta chain contains all the polymorphism
s specifying the peptide binding specificities. Hundreds of DRB1 allele
s have been described and typing for these polymorphisms is routinely done for bone marrow and kidney transplantation.
and DRB5
. DRB1 is present in all individuals. Allelic variants of DRB1 are linked with either none or one of the genes DRB3, DRB4 and DRB5. There are 4 related pseudogenes: DRB2, DRB6, DRB7, DRB8 and DRB9.
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
that in humans is encoded by the HLA-DRB1 gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
. DRB1 encodes the most prevalent beta subunit of HLA-DR.
Function
The proteinProtein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
encoded by this gene belongs to the HLA class II
MHC class II
MHC Class II molecules are found only on a few specialized cell types, including macrophages, dendritic cells and B cells, all of which are professional antigen-presenting cells ....
beta chain paralogues. The class II molecule is a heterodimer consisting of an alpha (DRA) and a beta chain (DRB), both anchored in the membrane. It plays a central role in the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
by presenting peptides derived from extracellular proteins. Class II molecules are expressed in antigen presenting cells (APC: B lymphocytes, dendritic cells, macrophages).
Gene structure and polymorphisms
The beta chain is approximately 26-28 kDa. It is encoded by 6 exonExon
An exon is a nucleic acid sequence that is represented in the mature form of an RNA molecule either after portions of a precursor RNA have been removed by cis-splicing or when two or more precursor RNA molecules have been ligated by trans-splicing. The mature RNA molecule can be a messenger RNA...
s, exon one encodes the leader peptide, exons 2 and 3 encode the two extracellular domains
Protein domain
A protein domain is a part of protein sequence and structure that can evolve, function, and exist independently of the rest of the protein chain. Each domain forms a compact three-dimensional structure and often can be independently stable and folded. Many proteins consist of several structural...
, exon 4 encodes the transmembrane
Transmembrane protein
A transmembrane protein is a protein that goes from one side of a membrane through to the other side of the membrane. Many TPs function as gateways or "loading docks" to deny or permit the transport of specific substances across the biological membrane, to get into the cell, or out of the cell as...
domain and exon 5 encodes the cytoplasm
Cytoplasm
The cytoplasm is a small gel-like substance residing between the cell membrane holding all the cell's internal sub-structures , except for the nucleus. All the contents of the cells of prokaryote organisms are contained within the cytoplasm...
ic tail. Within the DR molecule the beta chain contains all the polymorphism
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
s specifying the peptide binding specificities. Hundreds of DRB1 allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...
s have been described and typing for these polymorphisms is routinely done for bone marrow and kidney transplantation.
Gene expression
DRB1 is expressed at a level five times higher than its paralogues DRB3, DRB4HLA-DRB4
Major histocompatibility complex, class II, DR beta 4, also known as HLA-DRB4, is a human gene.- Function :The protein encoded by this gene belongs to the HLA class II beta chain paralogues. The class II molecule is a heterodimer consisting of an alpha and a beta chain , both anchored in the...
and DRB5
HLA-DRB5
HLA class II histocompatibility antigen, DRB5 beta chain is a protein that in humans is encoded by the HLA-DRB5 gene.- Function :The protein encoded by this gene belongs to the HLA class II beta chain paralogues. The class II molecule is a heterodimer consisting of an alpha and a beta chain , both...
. DRB1 is present in all individuals. Allelic variants of DRB1 are linked with either none or one of the genes DRB3, DRB4 and DRB5. There are 4 related pseudogenes: DRB2, DRB6, DRB7, DRB8 and DRB9.