Beta-2-Microglobulin (b2M)
BMG; B2MG
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). β
2 microglobulin lies lateral to the α
3 chain on the cell surface. Unlike α
3, β
2 has no transmembrane region. Directly above β
2 lies the α
1 chain, which itself is lateral to the α
2. β
2 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.
The complete amino acid sequence of the beta-2-microglobulin protein. It is a single polypeptide chain with a molecular mass of 11.6 kD that shows homology to immunoglobulins and HLA, suggesting a common evolutionary origin.