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
Symbol(s)	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
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Orthologs
	Human	Mouse
Entrez	567	12010
Ensembl	ENSG00000166710	ENSMUSG00000060802
Uniprot	P61769	Q3U679
Refseq	NM_004048 (mRNA) NP_004039 (protein)	NM_009735 (mRNA) NP_033865 (protein)
Location	Chr 15: 42.79 - 42.8 Mb	Chr 2: 121.84 - 121.84 Mb
Pubmed search	[1]	[2]

β₂ microglobulin is a component of MHC class I molecules, which are present on almost all cells of the body (red blood cells are a notable exception). 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.

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.

Further reading