Localization of the sites of iodination of human .beta.2-microglobulin; quaternary structure implications for histocompatibility antigens

Parker, Kenneth C.; Strominger, Jack L.

doi:10.1021/bi00274a024

Cited by 33 publications

(19 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Binding of an antibody at this site would leave the four-stranded /3 sheet of f82m free to interact with an Ig-like domain. It has also been observed that tyrosines 10, 26, and 63 ofhuman ,82m are iodinated in the free molecule but not when it is complexed with HLA heavy chain (46). In the three-dimensional structure, these protected side chains are exposed on the surface of the four-stranded p structure where they would be in noncovalent contact with the HLA heavy chain if these molecules formed a complex similar to those formed by CHl-CL and CH3-CH3.…”

Section: Resultsmentioning

confidence: 99%

Three-dimensional structure of beta 2-microglobulin.

Becker¹,

Reeke²

1985

Proc. Natl. Acad. Sci. U.S.A.

161

View full text Add to dashboard Cite

The three-dimensional structure of 132-microglobulin, the light chain of the major histocompatibility complex class I antigens, has been determined by x-ray crystallography. An electron density map of the bovine protein was calculated at a nominal resolution of 2.9 A by using the methods of multiple isomorphous replacement and electron density modification refinement. The molecule is approximately 45 x 25 x 20 A in size. Almost half of the amino acid residues participate in two large .3 structures, one of four strands and the other of three, linked by a central disulfide bond. The molecule thus strongly resembles Ig constant domains in polypeptide chain folding and overall tertiary structure. Amino acid residues that are the same in the sequences of 132-microglobulin and Ig constant domains are predominantly in the interior of the molecule, whereas residues conserved among 182-microglobulins from different species are both in the interior and on the molecular surface. In the crystals studied, the molecule is clearly monomeric, consistent with the observation that 132-microglobulin, unlike Ig constant domains, apparently does not form dimers in vivo but associates with the heavy chains of major histocompatibility complex antigens. Our results demonstrate that, at the level of detailed threedimensional structure, the light chain of the major histocompatibility class I antigens belongs to a superfamily of structures related to the Ig constant domains.032-microglobulin (,82m) was discovered in the urine of patients with chronic kidney dysfunction (1). It has since been found in a variety of physiological fluids as well as on the surfaces of nearly all cells as the light chain of the major histocompatibility complex (MHC) class I antigens of man (HLA) and other vertebrates (2-5). These antigens play central roles in two widely studied activities involving immune recognition by T cells: the rejection of foreign tissue grafts through direct recognition of foreign MHC antigens and the recognition of viral and other antigens in conjunction with self-MHC antigens (6)(7)(8). The MHC class I antigens display an extraordinary polymorphism that is the apparent basis for the diversity and specificity of these recognition events. The heavy chains of these antigens are integral membrane proteins, and their polymorphism is confined to their NH2-terminal 180 amino acid residues, those farthest from the cell surface. In contrast, 832m and the 90 extracellular residues closest to the membrane are highly conserved.Although the function of P32m in these antigens is unknown, there is evidence that its presence is necessary for posttranslational processing and insertion of HLA heavy chains into the membrane (9, 10). It also appears to stabilize the structure of the heavy chain in that its removal causes loss of alloantigenic sites on HLA (11,12 to those of Ig constant domains. These molecules include the T-cell differentiation antigen Thy-1 (24), the a and f3 chains of the T-cell antigen receptor (25-29), the MHC class I and II...

show abstract

Section: Resultsmentioning

confidence: 99%

Three-dimensional structure of beta 2-microglobulin.

Becker¹,

Reeke²

1985

Proc. Natl. Acad. Sci. U.S.A.

161

View full text Add to dashboard Cite

show abstract

“…Fe was prepared by the nitrilotriacetic acid method as described (40). Diferric Tf was labeled with 125 I by using iodogen (Pierce) as described (41).…”

Section: Methodsmentioning

confidence: 99%

Regulation of transferrin-mediated iron uptake by HFE, the protein defective in hereditary hemochromatosis

Waheed

Grubb

Zhou

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

124

View full text Add to dashboard Cite

The protein defective in hereditary hemochromatosis, called HFE, is similar to MHC class I-type proteins and associates with ␤2-microglobulin (␤2M). Its association with ␤2M was previously shown to be necessary for its stability, normal intracellular processing, and cell surface expression in transfected COS cells. Here we use stably transfected Chinese hamster ovary cell lines expressing both HFE and ␤ 2 M or HFE alone to study the effects of ␤ 2 M on the stability and maturation of the HFE protein and on the role of HFE in transferrin receptor 1 (TfR1)-mediated iron uptake. In agreement with prior studies on other cell lines, we found that overexpression of HFE, without overexpressing ␤2M, resulted in a decrease in TfR1-dependent iron uptake and in lower iron levels in the cells, as evidenced by ferritin and TfR1 levels measured at steady state. However, overexpression of both HFE and ␤2M had the reverse effect and resulted in an increase in TfR1-dependent iron uptake and increased iron levels in the cells. The HFE-␤2M complex did not affect the affinity of TfR1 for transferrin or the internalization rate of transferrin-bound TfR1. Instead, HFE-␤2M enhanced the rate of recycling of TfR1 and resulted in an increase in the steady-state level of TfR1 at the cell surface of stably transfected cells. We propose that Chinese hamster ovary cells provide a model to explain the effect of the HFE-␤2M complex in duodenal crypt cells, where the HFE-␤2M complex appears to facilitate the uptake of transferrin-bound iron to sense the level of body iron stores. Impairment of this process in duodenal crypt cells leads them to be iron poor and to signal the differentiating enterocytes to take up iron excessively after they mature into villus cells in the duodenum of hereditary hemochromatosis patients.H ereditary hemochromatosis (HH) is an autosomal recessive disorder of iron metabolism, characterized by excessive absorption of dietary iron in the small intestine. The excess iron is stored in the parenchymal cells of major tissues, primarily the liver, pancreas, heart, pituitary, and joints, eventually leading to severe tissue damage (1-3). The pathogenesis of HH is thought to involve a defect in the mechanism controlling iron absorption in the small intestine (4).The gene defective in hemochromatosis, HFE, encodes an MHC class I-type protein (5). In multiple population studies, 85-90% of HH patients of northern European ancestry were found to be homozygous for the C282Y mutation in HFE. About 5% are compound heterozygotes for C282Y and a second mutation, H63D (5-10). Even earlier, the observation that ␤ 2 -microglobulin (␤ 2 M)-deficient mice develop progressive iron overload similar to that seen in HH patients suggested the involvement of an MHC class I protein in HH (11, 12). Confirmation that mutations in HFE cause HH was provided by observations of mice with targeted disruption of the HFE gene. These HFE knockout mice showed high transferrin saturation and an increase in iron storage in hepatocytes (13-15).The C282Y mutati...

show abstract

“…Proteins (0.5-1 g) were iodinated with IODO-GEN as described previously (38). For deglycosylation experiments, total BHK21 extracts were solubilized and incubated in the presence or absence of 1 milliunit of peptide N-glycosidase F (PNGase F) or 5 milliunits of endoglycosidase H (endo H, Roche Applied Science) according to the manufacturer's protocol.…”

mentioning

confidence: 99%

Defective Endoplasmic Reticulum-resident Membrane Protein CLN6 Affects Lysosomal Degradation of Endocytosed Arylsulfatase A

Heine

Koch

Storch

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Variant late infantile neuronal ceroid lipofuscinosis, a lysosomal storage disorder characterized by progressive mental deterioration and blindness, is caused by mutations in a polytopic membrane protein (CLN6) with unknown intracellular localization and function. In this study, transient transfection of BHK21 cells with CLN6 cDNA and immunoblot analysis using peptide-specific CLN6 antibodies demonstrated the expression of a ϳ27-kDa protein that does not undergo proteolytic processing. Cross-linking experiments revealed the presence of CLN6 dimers. Using double immunofluorescence microscopy, epitope-tagged CLN6 was shown to be retained in the endoplasmic reticulum (ER) with no colocalization with the cis-Golgi or lysosomal markers. The translocation into the ER and proper folding were confirmed by the N-linked glycosylation of a mutant CLN6 polypeptide. Pulse-chase labeling of fibroblasts from CLN6 patients and from sheep (OCL6) and mouse (nclf) models of the disease followed by immunoprecipitation of cathepsin D indicated that neither the synthesis, sorting nor the proteolytic processing of this lysosomal enzyme was affected in CLN6-defective cells. However, the degradation of the endocytosed index protein arylsulfatase A was strongly reduced in all of the mutant CLN6 cell lines compared with controls. These data suggest that defects in the ER-resident CLN6 protein lead to lysosomal dysfunctions, which may result in lysosomal accumulation of storage material.

show abstract

Localization of the sites of iodination of human .beta.2-microglobulin; quaternary structure implications for histocompatibility antigens

Cited by 33 publications

References 21 publications

Three-dimensional structure of beta 2-microglobulin.

Three-dimensional structure of beta 2-microglobulin.

Regulation of transferrin-mediated iron uptake by HFE, the protein defective in hereditary hemochromatosis

Defective Endoplasmic Reticulum-resident Membrane Protein CLN6 Affects Lysosomal Degradation of Endocytosed Arylsulfatase A

Contact Info

Product

Resources

About