Beta-2 microglobulin

Beta-2-microglobulin
PDB rendering based on 1a1m.
Available structures
1a1m, 1a1n, 1a1o, 1a6z, 1a9b, 1a9e, 1agb, 1agc, 1agd, 1age, 1agf, 1akj, 1ao7, 1b0g, 1b0r, 1bd2, 1c16, 1ce6, 1cg9, 1de4, 1duy, 1duz, 1e27, 1e28, 1eey, 1eez, 1efx, 1exu, 1gzp, 1gzq, 1hhg, 1hhh, 1hhi, 1hhj, 1hhk, 1hla, 1hsa, 1hsb, 1i1f, 1i1y, 1i4f, 1i7r, 1i7t, 1i7u, 1im3, 1im9, 1jf1, 1jgd, 1jge, 1jht, 1jnj, 1k5n, 1kpr, 1ktl, 1lds, 1lp9, 1m05, 1m6o, 1mhe, 1mi5, 1n2r, 1of2, 1oga, 1ogt, 1onq, 1p7q, 1py4, 1q94, 1qew, 1qlf, 1qqd, 1qr1, 1qrn, 1qse, 1qsf, 1qvo, 1r3h, 1s8d, 1s9w, 1s9x, 1s9y, 1sys, 1syv, 1t1w, 1t1x, 1t1y, 1t1z, 1t20, 1t21, 1t22, 1tmc, 1tvb, 1tvh, 1uqs, 1uxs, 1uxw, 1vgk, 1w0v, 1w0w, 1w72, 1x7q, 1xh3, 1xr8, 1xr9, 1xz0, 1ydp, 1ypz, 1zhk, 1zhl, 1zs8, 1zsd, 1zt4, 1zvs, 2a83, 2ak4, 2av1, 2av7, 2axf, 2axg, 2bck, 2bnq, 2bnr, 2bsr, 2bss, 2bst, 2bsu, 2bsv, 2bvo, 2bvp, 2bvq, 2c7u, 2cii, 2cik, 2clr, 2d31, 2d4d, 2d4f, 2dyp, 2esv, 2f53, 2f54, 2f74, 2f8o, 2fyy, 2fz3, 2git, 2gj6, 2h26, 2h6p, 2hjk, 2hjl, 2hla, 2hn7, 2nw3, 2nx5, 3hla
Identifiers
Symbols	B2M;
External IDs	OMIM: 109700 MGI: 88127 HomoloGene: 2987
Gene ontology Molecular function • protein binding Cellular component • extracellular region • MHC class I protein complex Biological process • antigen processing and presentation of peptide antigen via MHC class I • immune response
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	567	12010
Ensembl	ENSG00000166710	ENSMUSG00000060802
UniProt	P61769	Q3U679
RefSeq	NM_004048 (mRNA)	NM_009735 (mRNA)
	NP_004039 (protein)	NP_033865 (protein)
Location	Chr 15: 42.79 - 42.8 Mb	Chr 2: 121.84 - 121.84 Mb
PubMed search	[1]	[2]

β₂ microglobulin also known as B2M is a component of MHC class I molecules, which are present on all nucleated cells (but not red blood cells).^[1][2]

Structure and function

Schematic representation of MHC class I

β₂ microglobulin lies lateral to the α₃ chain on the cell surface. Unlike α₃, β₂ has no transmembrane region. Directly above β₂ (i.e. away from the cell) lies the α₁ chain, which itself is lateral to the α₂.

β₂ microglobulin associates not only with the alpha chain of MHC class I molecules, but also with class I-like molecules such as CD1 and Qa.

Clinical significance

In patients on long-term hemodialysis, it can aggregate into amyloid fibers that deposit in joint spaces, a disease known as dialysis-related amyloidosis.

Mice models deficient for the β₂ microglobulin gene have been engineered. These mice demonstrate that β₂ microglobulin is necessary for cell surface expression of MHC class I and stability of the peptide binding groove. In fact, in the absence of β₂ microglobulin, very limited amounts of MHC class I (classical and non-classical) molecules can be detected on the surface. In the absence of MHC class I, CD8 T cells cannot develop. (CD8 T cells are a subset of T cells involved in the development of acquired immunity.)

Levels of beta-2 microglobulin can be elevated in multiple myeloma and lymphoma^[3], though in these cases primary amyloidosis (amyloid light chain) and secondary amyloidosis (Amyloid associated protein) are more common.

References

Further reading

v • d • e PDB Gallery 1a1m: MHC CLASS I MOLECULE B*5301 COMPLEXED WITH PEPTIDE TPYDINQML FROM GAG PROTEIN OF HIV2   1a1n: MHC CLASS I MOLECULE B*3501 COMPLEXED WITH PEPTIDE VPLRPMTY FROM THE NEF PROTEIN (75-82) OF HIV1   1a1o: MHC CLASS I MOLECULE B*5301 COMPLEXED WITH PEPTIDE LS6 (KPIVQYDNF) FROM THE MALARIA PARASITE P. FALCIPARUM   1a6z: HFE (HUMAN) HEMOCHROMATOSIS PROTEIN   1a9b: DECAMER-LIKE CONFORMATION OF A NANO-PEPTIDE BOUND TO HLA-B3501 DUE TO NONSTANDARD POSITIONING OF THE C-TERMINUS   1a9e: DECAMER-LIKE CONFORMATION OF A NANO-PEPTIDE BOUND TO HLA-B3501 DUE TO NONSTANDARD POSITIONING OF THE C-TERMINUS   1agb: ANTAGONIST HIV-1 GAG PEPTIDES INDUCE STRUCTURAL CHANGES IN HLA B8-HIV-1 GAG PEPTIDE (GGRKKYKL-3R MUTATION)   1agc: ANTAGONIST HIV-1 GAG PEPTIDES INDUCE STRUCTURAL CHANGES IN HLA B8-HIV-1 GAG PEPTIDE (GGKKKYQL-7Q MUTATION)   1agd: ANTAGONIST HIV-1 GAG PEPTIDES INDUCE STRUCTURAL CHANGES IN HLA B8-HIV-1 GAG PEPTIDE (GGKKKYKL-INDEX PEPTIDE)   1age: ANTAGONIST HIV-1 GAG PEPTIDES INDUCE STRUCTURAL CHANGES IN HLA B8-HIV-1 GAG PEPTIDE (GGKKKYRL-7R MUTATION)   1agf: ANTAGONIST HIV-1 GAG PEPTIDES INDUCE STRUCTURAL CHANGES IN HLA B8-HIV-1 GAG PEPTIDE (GGKKRYKL-5R MUTATION)   1akj: COMPLEX OF THE HUMAN MHC CLASS I GLYCOPROTEIN HLA-A2 AND THE T CELL CORECEPTOR CD8   1ao7: COMPLEX BETWEEN HUMAN T-CELL RECEPTOR, VIRAL PEPTIDE (TAX), AND HLA-A 0201   1b0g: CLASS I HISTOCOMPATIBILITY ANTIGEN (HLA-A2.1)/BETA 2-MICROGLOBULIN/PEPTIDE P1049 COMPLEX   1b0r: CRYSTAL STRUCTURE OF HLA-A*0201 COMPLEXED WITH A PEPTIDE WITH THE CARBOXYL-TERMINAL GROUP SUBSTITUTED BY A METHYL GROUP   1bd2: COMPLEX BETWEEN HUMAN T-CELL RECEPTOR B7, VIRAL PEPTIDE (TAX) AND MHC CLASS I MOLECULE HLA-A 0201   1c16: CRYSTAL STRUCTURE ANALYSIS OF THE GAMMA/DELTA T CELL LIGAND T22   1ce6: MHC CLASS I H-2DB COMPLEXED WITH A SENDAI VIRUS NUCLEOPROTEIN PEPTIDE   1cg9: COMPLEX RECOGNITION OF THE SUPERTYPIC BW6-DETERMINANT ON HLA-B AND-C MOLECULES BY THE MONOCLONAL ANTIBODY SFR8-B6   1de4: HEMOCHROMATOSIS PROTEIN HFE COMPLEXED WITH TRANSFERRIN RECEPTOR   1duy: CRYSTAL STRUCTURE OF HLA-A*0201/OCTAMERIC TAX PEPTIDE COMPLEX   1duz: HUMAN CLASS I HISTOCOMPATIBILITY ANTIGEN (HLA-A 0201) IN COMPLEX WITH A NONAMERIC PEPTIDE FROM HTLV-1 TAX PROTEIN   1e27: NONSTANDARD PEPTIDE BINDING OF HLA-B*5101 COMPLEXED WITH HIV IMMUNODOMINANT EPITOPE KM1(LPPVVAKEI)   1e28: NONSTANDARD PEPTIDE BINDING OF HLA-B*5101 COMPLEXED WITH HIV IMMUNODOMINANT EPITOPE KM2(TAFTIPSI)   1eey: Crystal Structure Determination Of HLA A2 Complexed to Peptide GP2 with the substitution (I2L/V5L/L9V)   1eez: Crystal Structure Determination of HLA-A2.1 Complexed to GP2 Peptide Variant(I2L/V5L)   1efx: STRUCTURE OF A COMPLEX BETWEEN THE HUMAN NATURAL KILLER CELL RECEPTOR KIR2DL2 AND A CLASS I MHC LIGAND HLA-CW3   1exu: CRYSTAL STRUCTURE OF THE HUMAN MHC-RELATED FC RECEPTOR   1gzp: CD1B IN COMPLEX WITH GM2 GANGLIOSIDE   1gzq: CD1B IN COMPLEX WITH PHOPHATIDYLINOSITOL   The maximum number of images (30) is exceeded !

External links

• MeSH beta+2-Microglobulin

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