Isolation and identification of a cDNA clone coding for an HLA-DR transplantation antigen alpha-chain

Membrane-bound mRNA was isolated from Raji cells and enriched for message coding for the HLA-DR transplantation antigen alpha-chain by sucrose gradient centrifugation. Double-stranded cDNA was constructed from this mRNA fraction, ligated to plasmid pBR322, and cloned into Escherichia coli. By hybrid selection, a plasmid, pDR-alpha-1, able to hybridize with mRNA coding for the HLA-DR alpha-chain was identified. From the nucleotide sequence of one end of the insert an amino acid sequence was predicted which is identical to part of the amino-terminal sequence of an HLA-DR alpha-chain preparation isolated from Raji cells. This clearly shows that pDR-alpha-1 carries almost the complete message for an HLD-DR alpha-chain. From the nucleotide sequence of this plasmid it will be possible to predict the primary structure of an HLA-DR alpha-chain.

Alpha chain of HLA-DR transplantation antigens is a member of the same protein superfamily as the immunoglobulins

Four cDNA clones, pDR-alpha-1, pDR-alpha-2, pDR-alpha-3 and pDR-alpha-4, corresponding to the alpha chain of HLA-DR antigens, have been sequenced. Restriction maps and sequences suggest that all clones are identical apart from a single-base substitution present in pDR-alpha-1. Amino acid sequence data, together with the nucleotide sequence data, allowed the complete amino acid sequence to be predicted. The alpha chain is composed of 229 amino acids, of which 191 are exposed on the outside of the plasma membrane. The membrane-embedded portion of the chain consists of 23 hydrophobic amino acids. The succeeding 15 amino acids form the cytoplasmically localized hydrophilic tail. The extracellular portion, with carbohydrate moieties linked to Asn78 and Asn118, seems to be organized into two domains. The second domain, which contains the only disulfide bond of the alpha chain, displays amino acid sequence homology to immunoglobulin constant regions, to the second domain of the beta chain of a class II antigen, to the third domain of heavy chains of class I antigens and to beta 2-microglobulin. Thus the subunits of immunoglobulins, class I antigens and class II antigens are related evolutionarily.

Complete amino acid sequence of an HLA-DR antigen-like beta chain as predicted from the nucleotide sequence: similarities with immunoglobulins and HLA-A, -B, and -C antigens

The complete nucleotide sequence of an HLA-DR antigen-like beta-chain cDNA clone was determined. The 1,080 base pairs include the complete coding region and most of the untranslated portion. The predicted amino acid sequence has 229 residues. The beta chain contains two immunoglobulin-like disulfide loops and a 21-amino acid residue membrane-integrated segment. Ten amino acid residues reside on the cytoplasmic side of the plasma membrane. The single asparagine-linked carbohydrate moiety is attached to asparagine-19. The NH2-terminal 91 residues of the beta chain are homologous to the corresponding region of HLA-A, -B, and -C antigen heavy chains. Residues 92-192 of the beta chain display statistically significant homology to members of the immunoglobulin family, beta 2-microglobulin, and the immunoglobulin-like domain of HLA-A, -B, and -C antigen heavy chains. These data establish that the major histocompatibility antigens of class I and class II type and the constant regions of immunoglobulins are evolutionarily related.

Isolation and identification of a cDNA clone corresponding to an HLA-DR antigen beta chain

The HLA-D locus in the major histocompatibility complex controls the expression of the genetically polymorphic HLA-DR antigens. mRNA coding for the beta chains of these antigens was partially purified from the human lymphoblastoid cell line Raji. The mRNA was copied into double-stranded cDNA and cloned in Escherichia coli. One clone, pDR-beta-1, obtained by hybrid selection, carries a 1070-base-pair insert comprising all of the coding region except the signal sequence and a substantial portion of the untranslated region. To identify pDR-beta-1, highly purified HLA-DR antigen beta chains derived from Raji cells were subjected to NH2-terminal amino acid sequence determination. This sequence displayed extensive homology with that deduced from the nucleotide sequence at the 5' end of the pDR-beta-1 coding region. Taken together, the amino acid and nucleotide sequences strongly argue in favor of Raji cells containing at least two beta-chain loci.

Evolutionary relationship between HLA-DR antigen beta-chains, HLA-A, B, C antigen subunits and immunoglobulin chains

cDNA for a beta-chain of HLA-DR antigens was cloned and the partial nucleotide sequence was determined. The data suggest that the beta-chain consists of approximately 230 amino acids, of which about 200 are exposed on the cell surface. The beta-chain appears to be composed of two exposed disulphide-containing domains. The arrangement of the disulphide loops suggests that the beta-chain is similar in structure to the HLA-A, B, C antigen subunits and the immunoglobulin chains. For the beta-chain domain closest to the membrane this similarity was verified at the level of primary structure. The partial amino acid sequence of the NH2-terminal domain did not display any apparent homology to HLA-A, B, C antigens and immunoglobulins. However, the similarity established here between the two types of major histocompatibility antigen subunits and the immunoglobulin chains suggests a common ancestral origin for at least some regions of these molecules.

Crystallization of and preliminary X-ray data for an intracellular vitamin A-binding protein from rat liver

Crystals of a cellular retinol-binding protein from rat liver have been grown from solutions of polyethylene glycol-6,000 and CdCl2. The crystals are orthorhombic, space group P212121, a = 40.09, b = 47.39, and c = 69.34 A. An asymmetric unit contains 1 molecule. Diffraction has been observed to Bragg spacings of 1.7 A resolution.

Role of beta2-microglobulin in the intracellular processing of HLA antigens

The biosynthesis of HLA-A, -B, and -C antigens was examined in the two lymphoblastoid cell lines DAUDI and RAJI. In RAJI cells the HLA-A, -B, and -C antigen heavy chains become core-glycosylated in the endoplasmic reticulum as evidenced by their sensitivity to endo-H digestion and tunicamycin treatment. Beta2-Microglobulin is present in excess in the endoplasmic reticulum of the RAJI cells and associates with the heavy chain at the time of synthesis of the heavy chain. Pulse-chase experiments demonstrated that the RAJI HLA-A, -B, and -C antigen heavy chains become terminally glycosylated since their changed characteristics included resistance to endo-H digestion, sensitivity to neuraminidase treatment, and incorporation fucose. DAUDI HLA-A, -B, and -C antigen heavy chains are synthesized normally and become core-glycosylated but not terminally glycosylated. Other glycosylated cell surface proteins, like the HLA-DR antigens, display normal glycosylation in DAUDI cells. Therefore it is unlikely that the absence of terminally glycosylated HLA-A, -B, and -C antigen heavy chains is the result of a general defect in the biosynthetic machinery of DAUDI cells. However, DAUDI cells lack the ability to synthesize beta2-microglobulin, the common subunit of all HLA-A, -B, and -C antigens. Therefore, it seems reasonable to conclude that beta2-microglobulin is of importance for intracellular transport of newly synthesized HLA-A, -B, and -C antigens.

cDNA clone coding for part of a mouse H-2d major histocompatibility antigen

mRNA coding for mouse major transplantation antigens of the d haplotype was partially purified, copied into double-stranded cDNA, and cloned in Escherichia coli. Clones were selected by their ability to hybridize specifically with mRNA coding for H-2K, D, or L antigens. One of these clones, pH-2d-1, carries a 1200-base-pair insert, comprising the noncoding region, including poly(A) at the 3' end and part of the coding region. A partial sequence of the latter region showed extensive homology with the known amino acid sequences of H-2Kb,Kk, and HLA-B7 antigens. From this comparison, it appears that the coding region extends from amino acid 133 in the second domain, through the third domain, to the cytoplasmic COOH-terminal region. A stretch of 24 hydrophobic or uncharged residues, located 31 amino acids from the COOH-terminal end, could represent the segment that spans the membrane. This is followed on the cytoplasmic side of the membrane by a cluster of basic amino acids and a possible phosphorylation site on a threonine residue.

On the stoichiometry of the interaction between prealbumin and retinol-binding protein

The stoichiometry of the interaction between prealbumin and retinol-binding protein was investigated. Gel chromatography analyses of prealbumin on columns equilibrated with retinol-binding protein (RBP)-containing buffers and fluorescence polarization analyses of RBP in the presence of various concentrations of prealbumin demonstrated that 3 molecules of RBP could simultaneously bind to prealbumin. Each RBP molecule seemed to interact with prealbumin with an apparent association constant of about 7.8 X 10(6) M-1. Fab fragments of anti-iudiotypic antibodies raised against anti-RBP antibodies reaced specifically with the RBP-binding sites on prealbumin. Two anti-idiotypic Fab fragments could simultaneously interact with prealbumin. These data strongly suggest that prealbumin exhibits at least two RBP-binding sites.

Binding of anti-idiotypic antibodies against human serum low density lipoprotein (LDL) to skin fibroblasts

Specific rabbit antibodies against human serum low density lipoproteins (LDL) were prepared. These were injected into guinea pigs and anti-idiotypic antibodies against human LDL were recovered. The anti-idiotypic antibodies inhibited the binding of (125)I-labeled LDL to human skin fibroblasts.

Complete amino acid sequence of pooled papain-solubilized HLA-A, -B, and -C antigens: relatedness to immunoglobulins and internal homologies

Pooled, papain-solubilized HLA-A, -B, and -C antigens, derived from a large number of individuals and comprising several allelic forms, have been subjected to amino acid sequence determination. Despite the heterogeneity of the material, a main sequence representing all of the 273 amino acid residues could be established. The primary structure encompasses two immunoglobulin-like disulfide loops. The single carbohydrate moiety is attached to asparagine-86. Computer analyses demonstrated that the COOH-terminal one-third of the sequence, called H3, display statistically significant homology with members of the immunoglobulin family. The NH2-terminal two-thirds of the molecule, called H1 and H2, are not significantly homologous to any of the immunoglobulin sequences. However, H1 and H2 exhibit a distant relatedness to each other but no obvious similarity to the H3 region.

Primary structure of pooled, papain-solubilized HLA-A, -B, and -C antigens

The tentative amino acid sequence of pooled, papain-solubilized HLA antigen heavy chains has been determined. The amino acid sequence comprises 273 residues. As the structural analyses were performed on HLA antigen heavy chains comprising a mixture of several allelic forms derived from the A, B, and possibly C loci, multiple residues were encountered in several positions. However, a quantitatively dominating residue could always be easily identified. The present data suggest that the amino acid variability of the HLA-A, -B, and -C antigens is found in restricted regions of the molecule. The COOH-terminal third of the HLA antigen heavy chain appears to be less variable than other regions of the molecule. Previous work has shown that the HLA antigen heavy chain contains two immunoglobulin-like disulphide loops. The COOH-terminal third of the heavy chain was shown to be similar in primary structure to beta 2-microglobulin and the immunoglobulin G constant domains.

Amino acid sequence of an immunoglobulin-like HLA antigen heavy chain domain

The classical human transplantation antigens, derived from the HLA-A, -B, and -C loci, are cell-surface-expressed glycoproteins. On the exterior of the cell the transplantation antigen heavy chain exposes two disulfide-containing domains and a glycosylated NH2-terminal extension. The disulfide-containing domain closest to the membrane has been isolated and its amino acid sequence has been determined. The HLA antigens used for the sequence analysis were derived from two and possibly three loci and comprised several allelic forms. The primary structure was remarkably invariant, and amino acid variations were observed only at three positions. Whether this suggests that the allelic variation of the HLA antigens is preferentially confined to other regions of the molecule or is a result of fortuitous selection of peptides remains to be established. The sequenced portion of the HLA antigen heavy chain is as homologous to beta 2-microglobulin and immunoglobulin light and heavy chains as are the latter to one another. This observation strengthens the notion that the transplantation antigens and the immunoglobulins are evolutionarily related.

Presence of alloreactive Ia antigens on murine intestine epithelial cells

Purified intestine epithelial cells express Ia antigens as determined by immunoprecipitation and sodium dodecyl sulphate polyacrylamide-gel electrophoresis. The intestinal Ia antigens react at least with alloantisera directed against the H-2 I-A subregion.

Chemical, physical-chemical, and immunological properties of papain-solubilized human transplatation antigens

Papain-solubilized HLA-A, -B, and -C antigens have been isolated from cadaveric spleens. The isolated material was homogeneous and comprised subunits with the apparent molecular weights 33,000 and 12,000. Amino acid analyses of a mixture of HLA antigen heavy chains obtained from a great number of spleens with different HLA antigen phenotypes revealed a composition that is very similar to that of individual HLA-A and -B antigens. Likewise, the NH2-terminal 30 residues of the HLA-antigen heavy chain mixture were virtually identical with that recorded for individual specificities. The circular dichroism spectra for the isolated HLA antigens and for free beta2-microglobulin revealed similarities with spectra recorded for immunoglobulin chains and domains. The HLA-antigen heavy chain may contain an appreciable amount of beta structure. Antibodies raised against free beta2-microglobulin react better with beta2-microglobulin in free form than when bound to the HLA-A, -B, and -C antigen heavy chains. This is due to the fact that free beta2-microglobulin can bind a maximum of four Fab fragments simultaneously, whereas the HLA-antigen-associated beta2-microglobulin can bind only two Fab fragments without dissociating from the heavy HLA-antigen subunit.