Disease relevance of B2M

• The complete sequence of bovine beta 2-microglobulin was determined using only one proteolytic enzyme, Staphylococcus aureus V8 protease [1].
• We find that the increased expression of Db molecules induced by influenza virus nucleoprotein residues 365-380 is similarly dependent on culturing RMA-S cells in bovine serum or with purified bovine beta 2-microglobulin [2].
• Beta 2 microglobulin enhances the infectivity of cytomegalovirus and when bound to the virus enables class I HLA molecules to be used as a virus receptor [3].
• We previously reported that a host protein, beta 2 microglobulin (beta 2m) inhibited the detection of human cytomegalovirus (CMV) in urine specimens by enzyme immunoassay and postulated that beta 2m bound to the virus particle and masked the viral antigenic determinants [4].
• Results revealed albumin was remarkable in the urine from a cow with glomerulonephritis, and beta2-microglobulin was, in the urine from a cow with tubular dysfunction [5].

High impact information on B2M

• The N-terminal amino acid sequence of the beta t purified from this cell line was shown to be indistinguishable from that of bovine beta 2m [6].
• Serum beta 2-microglobulin binds to a T-cell differentiation antigen and increases its expression [6].
• Like class I products of the human major histocompatibility complex, it has a glycosylated heavy (alpha) chain of approximately 45-50,000 molecular weight (MW) in non-covalent association with beta 2-microglobulin (beta 2m) (MW 11,900) [6].
• The mutant phenotype has been reported to be normalized upon incubation of RMA-S cells at 25 degrees C. We find that much of the increased expression of class I heterodimers is dependent on culturing RMA-S cells in bovine serum or with purified bovine beta 2-microglobulin [2].
• The three-dimensional structure of beta 2-microglobulin, the light chain of the major histocompatibility complex class I antigens, has been determined by x-ray crystallography [7].

Biological context of B2M

• Calves homozygous for one of the eight haplotypes ( B2M 2,2) were at increased risk of FPT (odds ratio = 10.60, CI(95%) 2.07-54.24, p = 0.005) [8].
• Twelve single nucleotide polymorphisms (SNPs), assorted into eight haplotypes, were identified by sequencing regions of B2M exons II and IV in a multi-breed panel of 96 beef cattle [8].
• Complete amino acid sequence of bovine beta 2-microglobulin [1].
• Nucleotide sequence of cattle beta 2-microglobulin cDNA [9].
• Bovine beta 2-microglobulin (beta 2-m), the light chain of the histocompatibility antigen, was isolated in crystalline form from colostrum [10].

Anatomical context of B2M

• beta 2-Microglobulin has been isolated and crystallized from bovine colostrum and represents the only crystalline form of this protein reported [1].
• Based on these findings we conclude that although beta 2M is present in bovine bone matrix extracts, it is not a mitogen for Ob-like cells [11].
• From an initial solution concentration of 50 mg/liter, both membranes adsorbed significantly more beta 2m than BSA at equilibrium (PAN, 352 +/- 30 vs. 32.1 +/- 2.4 ng; CT, 87.0 +/- 0.6 vs. 30.8 +/- 1.7 ng) [12].
• We have shown that CMV and beta 2m compete for binding sites on fibroblasts [3].
• We have previously demonstrated that human cytomegalovirus (CMV) binds the host protein beta 2 microglobulin (beta 2m) from body fluids or from cell culture media [3].

Associations of B2M with chemical compounds

• During the final purification of beta 2M by CN reverse phase HPLC the mitogenic activity for bone cells separated from the beta 2M protein peak [11].
• The ED50 of the bone-derived beta 2M (4,890 +/- 462 ng/ml) was several orders of magnitude (2 x 10(3) to 1.4 x 10(5) times) greater than the ED50 of simultaneously assayed purified growth factors and was no different from the ED50 of the crude EDTA matrix extract (3,350 +/- 890 ng/ml) [11].
• Purified TGF beta, beta 2 m, and IGF I migrated as single bands on polyacrylamide gel electrophoresis with respective molecular masses of 24,000, 10,000, and 7,500 [13].
• CA amyloid appeared to be potassium permanganate sensitive and tryptophan positive, and in this respect different from most other amyloid types except for AA and beta-2 microglobulin amyloid [14].
• It was found that the method using the beta 2-M-free urine as a diluent was more accurate than using PBS [15].

Other interactions of B2M

• A principal component of antibody transport is the neonatal receptor for the Fc portion of immunoglobulin, a heterodimer of a MHC-1 alpha-chain homolog ( FCGRT) and beta-2-microglobulin ( B2M) [8].
• In conclusion, adult bone matrix, like fetal bone cultures, contains TGF beta, beta 2 m, and IGF I and these factors may play a role in adult skeletal remodeling [13].
• BAMP is antigenically distinct from all adult serum proteins, free secretory component, beta 2-microglobulin, lactoferrin, alpha-lactalbumin, beta-lactoglobulin, and five different caseins [16].
• In addition the EPO adsorptive rate, as well as that of beta 2-microglobulin (beta 2-MG), was greater with a PMMA membrane than with a PAN membrane [17].

Analytical, diagnostic and therapeutic context of B2M

• To clarify the molecular states of beta 2-m, its solution properties were studied by ultracentrifugation and spectropolarimetry [10].
• Detection and quantitation of beta-2-microglobulin glycosylated end products in human serum by matrix-assisted laser desorption/ionization mass spectrometry [18].
• The assay, similar to that described previously for beta 2-microglobulin (Clin. Chem. 27:832-837, 1981), consists of incubating the sample at 37 degrees C for 30 min with antibody-coated particles, then quantifying the resulting agglutination by particle-counting or turbidimetry [19].
• CMV could also bind bovine beta 2m from foetal calf serum in cell culture fluids [4].
• A rapid and robust particle-enhanced turbidimetric immunoassay for serum beta 2 microglobulin [20].

References