A2-Microglobulin

Monitoring of Cd exposure can take place by the determination of Cd in whole blood (reflects recent exposure) or urine (reflects body burden) by GF-AAS. Early effects can be monitored by the determination of a tubular protein (e.g. 132-microglobulin, retinol binding protein, a2-microglobulin) or the activity of an enzyme (e.g. N-acetyl 3-D-glucosaminidase) in urine. 

DNA plasmid encoding HLA-B7 and a2-microglobulin Allovectin-7 Metastatic melanoma... 

The three-dimensional structure of a large fragment of a human MHC class I protein, human leukocyte antigen A2 (HLA-A2), was solved in 1987 by Don Wiley and Pamela Bjorkman. Class I MHC proteins consist of a 44-kd a chain noncovalently bound to a 12-kd polypeptide called P " microglobulin. The a chain has three extracellular domains (a j,... 

HLA-C (CTLs, Tc), presents endogenously synthesized peptides (e.g. virus coded peptides) microglobulin (Not a MHC protein) High degree of sequence variability in 1 and a2 domains ... 

Although little is known about the three-dimensional structure of MHC molecules, on the basis of primary sequence data as well as of preliminary crystallographic evidence [96] it can be assumed that their general structural plan is not very different from that of TcR s. Thus, they are composed of two different chains, a heavy (a) and a light (J3) chain, and consist of a membrane-distal domain, to which variability is essentially restricted, a membrane-proximal domain, which is essentially invariant, a transmembrane and an intracytoplasmic tail. Both extracellular domains result from the pairing of two units (Fig. 2) however, in class 1 both V domain units (al and a2) are contributed by the same chain (a), whilst the C domain is contributed by one a chain unit (a3) and by /T-microglobulin (which is not MHC encoded). In class II, both domains result from one a chain and one /3 chain unit (the V domain from al and (31 and the C domain from a2 and (32). Furthermore in class I molecules, but not in class II or T cell receptor molecules, the transmembrane and intracytoplasmic segments are not dimeric. 

Fig. 2. HLA class 1 molecules consist of a glycoprotein heterodimer comprising an a chain made up of three a domains covalently associated with (l2-microglobulin. The molecule traverses the cell membrane at one end only. Most of the polymorphism of the molecule is located within the al and a2 domains, which contain the peptide binding groove (see text and Fig. 3).

FIGURE 33.23 Class I MHC protein. A protein of this class consists of two chains. The a chain begins with two domains that include a helices (ai, a2), an immunoglobulin domain (aj), a transmembrane domain, and a cytoplasmic tail. The second chain, Pj-microglobulin, adopts an immunoglobulin fold. 

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