B2M protein – Human Beta-2-microglobulin(B2M) Recombinant Protein

General information on B2M protein

B2M protein also known as β2 microglobulin is a component of major histocompatibility complex (MHC) class I molecules. Beta 2-microglobulin is encoded by B2M gene in humans. MHC class I molecules are located in all nucleated cells as well as in platelets but not in red blood cells. The function of MHC class I molecules is to bind peptide fragments from pathogens and display them on the cell surface. The peptides are then recognized by the appropriate immune cells. The peptides presented by MHC class I are generated from cytosolic protein which are translocated into the endoplasmic reticulum by TAP molecules. The latter are transporters involved in antigen processing. It is believed that B2M dimerizes and physically attaches to TAP molecules and is further released for transport where it binds the peptide. The dimerization of B2M proteins is mediated by the chaperone calnexin. The association with beta 2-microglobulin is essential for the transport of class I heavy chains from the endoplasmic reticulum to the cell surface.

MHC class I molecule consists of β2 microglobulin and three α proteins, more precisely α1, α2, and α3 proteins. Beta 2-microglobulin constitutes the light chain of these MHC molecules. β2 microglobulin lies beside the α3 chain. Unlike the latter, B2M protein has no transmembrane region. β2 microglobulin is also located under α1 chain on the cell surface. However, B2M protein is not directly linked to α2 chain. B2M protein binds to different alpha chains via non-covalent bonds. Other associations of B2M protein include molecules such as CD1 and Qa.

B2M protein is present in small amounts in the serum, in the cerebrospinal fluid, and in urine of healthy individuals. However, this protein is present to a much greater degree in the plasma and the urine of patients with tubular proteinuria, renal failure, or kidney transplants.