Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of Ca2+ to a salivary phosphoprotein, protein C, was studied by equilibrium dialysis. In 5mM-Tris/HCl buffer, pH 7.5, protein C bound 190 nmol of Ca2+/mg of protein. The apparent dissociation constant, K, was determined to be 1.9 x 10(-4)M and the binding of Ca2+ to the protein was non-co-operative. The binding of Ca2+ to protein C apparently depends on groups which ionize above pH 5.0. Ca2+ binding decreased with increased concentration of the dialysis buffer and on addition of SrCL2, MgCl2 and MnCl2 to the dialysis buffer. Digestion of protein C with trypsin or collagenase or heating of the protein to 60 degrees or 100 degrees C had little or no effect on the Ca2+ binding. Digestion of protein C with alkaline phosphatase caused a decrease in the amount of protein-bound Ca2+. This was also found for another salivary phosphoprotein, protein A. In the absence of Ca2+ the S020,w for protein C was 1.29 S and in the presence of Ca2+ it was 1.46S. Ca2+ may cause a conformational change in the protein or an aggregation of the protein molecules. No conformational changes of protein C in the presence of Ca2+ could be detected by circular dichroism or nuclear magnetic resonance.
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PMID:The binding of calcium to a salivary phosphoprotein, protein C, and comparison with calcium binding to protein A, a related salivary phosphoprotein. 1 96

The binding of Ca2+ to a previously described phosphoprotein from human parotid saliva, protein A [Bennick (1975) Biochem J. 145, 557-567] was studied by means of equilibrium dialysis. In 5 mM-Tris/HC1 buffer, pH7.5, protein A bound 664nmol of Ca/mg of protein. Km was determined to be 181 muM and the binding of Ca2+ to the protein was non-co-operative. The binding of Ca2+ apparently occurs to side-chain carboxyl groups in the protein, but protein phosphate is of minor if any importance in calcium binding. Hydrolysis of protein A by trypsin and collagenase or heating of the protein at 60 degrees or 100 degrees C did not affect Ca2+ binding. The Ca2+ binding decreases with increased concentration of the dialysis buffer and on the addition of SrCl2, or MgCl2 or MnCl2 to the dialysis buffer. Protein A does not aggregate in the presence of Ca2+, since the s20,w was identical when determined in the presence (1.30S) and absence (1.35S) of CaCl2. By use of a specific antiserum to protein A it was found that protein C [Bennick & Connell (1971) Biochem. J. 123, 455-464] and perhaps minor related components cross-reacted with protein A. No other salivary proteins showed immunological similarity. Proteins A and C were also present in submandibular saliva. The possible functions of protein A are discussed.
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PMID:The binding of calcium to a salivary phosphoprotein, protein A, common to human parotid and submandibular secretions. 18 Sep 80

The isolation of a highly purified phosphoprotein, previously named protein C, from human parotid saliva is described. A chemical and physical characterization of protein C was undertaken and the properties of protein C were compared with those of a related protein A. The content of glycine, proline and dicarboxylicamino acids accounts for 83% of the total resideus of protein C and it contains 2.0 mol of P/mol of protein, most likely as phosphoserine. The protein also contains 1.2% glucose, but no hexosamine. The N-terminus is blocked and the proposed C-terminal sequence is -Ser(Gly, Pro)Gln. The molecular weight determined from ultracentrifugation is 16300. Circular dichroism and nuclear magnetic resonance fail to demonstrate the presence of polyproline structure, and there are no conformational changes under a variety of conditions. With specific antisera to protein C the protein can be detected in submandibular as well as in parotid saliva, but there is only reaction of partial identity of proteins A and C. It is proposed that at least part of the difference between proteins A and C is due to the presence of an additional length of peptide at the C-terminus of protein C.
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PMID:Chemical and physical characterization of a phosphoprotein, Protein C, from human saliva and comparison with a related protein A. 86 25

The subcellular localization of the nonstructural protein C of Sendai virus was investigated by means of indirect immunofluorescence microscopy of Sendai virus-infected cells, using an antiserum specific for C protein. In infected cells, C protein was detected exclusively in the cytoplasm as granular fluorescence, which coincided very well with the distribution of nucleocapsid protein NP and phosphoprotein P, which were also detected with specific antisera. This suggested that these proteins are present together in inclusions, probably forming nucleocapsids. In contrast, when the NP and C proteins were individually expressed in COS cells by transfection with expression plasmids containing cDNA for these proteins, their distribution patterns in the cytoplasm were found to be quite different from each other. Protein-blot analyses of purified virions revealed the presence of a significant amount of the C protein in virions, which indicated that C protein is integrated into virions. Under conditions in which most of the envelope-associated proteins, such as HN, F, and M, were removed from the virions by a detergent, the C protein remained tightly associated with the nucleocapsids--about 40 molecules per nucleocapsid.
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PMID:Association of the Sendai virus C protein with nucleocapsids. 217 59

The complete nucleotide sequence of the P + C mRNA of human parainfluenza virus type 3 (PF3) was determined by sequencing cDNA, viral genomic RNA and mRNA. The P + C mRNA is 2009 nucleotides in length, exclusive of poly(A), and contains two overlapping open reading frames (ORFs). The P + C mRNA encodes two proteins, the 602 amino acid nucleocapsid phosphoprotein P and the 199 amino acid non-structural protein C. Peptide mapping confirmed that the two proteins are unrelated. Hybrid-arrest translation experiments assigned each of the two proteins to its respective ORF. These studies showed that the coding strategy of the PF3 P + C mRNA is similar to that of Sendai virus. Amino acid sequence alignment showed that the P and C proteins of PF3 and Sendai virus represent homologous pairs. However, these homologies are represented by high contents of accepted amino acid substitutions and by similarity in hydropathy profiles rather than by high contents of exact amino acid matches. Homology with the P and C proteins of measles, canine distemper and respiratory syncytial viruses was at the threshold of significance. The patterns of amino acid sequence homology among the paramyxovirus HN, F, NP, P and C proteins are compared.
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PMID:Sequence analysis of the P and C protein genes of human parainfluenza virus type 3: patterns of amino acid sequence homology among paramyxovirus proteins. 302 46

A basic proline-rich peptide, P-C, was isolated from human whole saliva and its amino acid sequence was determined to be Gly-Arg-Pro-Gln-Gly-Pro-Pro-Gln-Gln-Gly-Gly-His-Gln-Gln-Gly-Pro-Pro-Pro-Pro-Pro-Pro-Gly-Lys-Pro-Gln-Gly-Pro-Pro-Pro-Gln-Gly-Gly-Arg-Pro-Gln-Gly-Pro-Pro-Gln-Gly-Gln-Ser-Pro-Gln. P-C was also found to be present in stimulated parotid saliva. The sequence determined appears to correspond to the C-terminal 44 residues of a proline-rich phosphoprotein, Protein C, the partial sequence of which has been elucidated, and suggests that P-C might be derived from Protein C.
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PMID:The amino acid sequence of a salivary proline-rich peptide, P-C, and its relation to a salivary proline-rich phosphoprotein, protein C. 739 Sep 79

The stimulation of normal human PBMC by Trypanosoma cruzi Ag was analyzed. PBMC showed significant in vitro proliferation in response to parasite lysate (Tct), with stimulation indices ranging from 10 to 400, peaking at 6 to 7 days. The cells stimulated with Tct produced significant levels of IL-2. To determine which cells proliferated in response to Tct, PBMC were separated into T- and B-enriched cell populations. Purified T cells, but not B cells, proliferated strongly to Tct. The T cell response required APC and was processing dependent. T cell lines generated against Tct proliferated in response to parasite lysate only in the presence of autologous APC and produced IL-2, IL-6, and IFN-gamma but not IL-4 in response to PMA plus ionomycin. Although there were a significant number of CD45Ra+ cells, the majority of the cells in these T cell lines were CD45Ro+. The V beta usage of Tct-responding T cells was heterogeneous, with most V beta genes represented among the responding cells. An immunodominant repeat Ag (TcD) and a ribosomal phosphoprotein (P0) of T. cruzi elicited strong proliferative responses in all subjects tested. These data indicate the presence of T cell-stimulatory Ag in Tct, characterized by nonpreferential usage of the V beta gene families. The strong stimulation of normal human PBMC by Tct may contribute to immunologic alterations seen in T. cruzi infection.
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PMID:Characterization of responses of normal human T cells to Trypanosoma cruzi antigens. 842 47

CD28 is a major T cell costimulatory molecule, delivering signals distinct from those of the CD3/TCR complex, which regulate cytokine and cytokine receptor expression, cell proliferation, and cell viability. CD28 needs to be cross-linked to initiate signals, yet both of its ligands, CD80 and CD86, are expressed as monomers. Previously, we determined the cytoplasmic tail of CD80 is required for CD28-mediated costimulation and subcellular relocalization of CD80 in lymphocytes. In this study, we report that Reh B cell transfectants expressing CD80 with mutations in the cytoplasmic tail region either at 275-278 (RRNE-->AAAA, CD80/4A) or serine 284 (S-->A, CD80/SA) can bind ligand similar to transfectants expressing wild-type CD80, yet are unable to costimulate T cell proliferation. These mutant CD80 molecules are expressed on the surface of the Reh cells in small clusters or foci indistinguishable from those of wild-type CD80 molecules. However, mutant CD80 molecules unlike wild-type CD80 cannot be readily induced by ligand into caps. Thus, small clusters of CD80 found on APC are insufficient to initiate CD28-mediated signals, and the formation of CD80 caps appears to be a critical factor regulating the initiation of T cell costimulation. A 30-kDa phosphoprotein that associates with the cytoplasmic tail of CD80 in activated cells may play a role in CD80 redistribution and thus CD28-mediated costimulation. These results indicate two distinct regions of the CD80 cytoplasmic tail regulate its costimulatory function, and both regions are required for CD80 function.
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PMID:Two regions in the CD80 cytoplasmic tail regulate CD80 redistribution and T cell costimulation. 974 26

Potent and readily accessible APC are critical for development of immunotherapy protocols to treat viral disease and cancer. We have shown that B lymphoblastoid cell lines (BLCL) that stably express CMV phosphoprotein 65 (BLCLpp65), as a result of retroviral transduction, can be used to generate ex vivo CTL cultures that possess cytotoxicity against CMV and EBV. In this report, we demonstrate that the EBV-specific cytotoxicity in the BLCLpp65-primed culture had a spectrum of EBV-Ag recognition similar to that of the BLCL-primed counterpart, suggesting that retroviral transduction and expression of the CMV Ag would not compromise the Ag-presenting capacity of BLCL. In addition, BLCLpp65 appeared to present multiple natural pp65 epitopes, because pp65-specific CTL, which recognized different CMV clinical isolates, were generated in BLCLpp65-primed cultures from individuals with various HLA backgrounds. Consistent with a polyclonal expansion of virus-specific CTL, T cell lines established from the BLCLpp65-primed CTL cultures expressed different TCR-Vbeta Although most of the virus-specific T cell isolates were CD8+, EBV-specific CD4+ lines were also established from BLCLpp65-primed cultures. Western blot analysis revealed that the CD8+ lines, but not the CD4+ line, expressed granzyme B, consistent with features of classic CTL. Thus, our results suggested that BLCL stably expressing a foreign Ag might be used as a practical APC to elicit CD8+ T cell responses.
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PMID:B lymphoblastoid cell lines as efficient APC to elicit CD8+ T cell responses against a cytomegalovirus antigen. 1103 22

The two main constraints that currently limit a broader usage of T cell therapy against viruses are the delay required to obtain specific T cells and the safety of the selection procedure. In the present work we developed a generally applicable strategy that eliminates the need for APC for timing reasons, and the need for infectious viral strains for safety concerns. As a model, we used the selection of T lymphocytes specific for the immunodominant CMV phosphoprotein pp65. PBMC from healthy seropositive donors were first depleted of IL-2R alpha-chain CD25(+) cells and were then stimulated for 24-96 h with previously defined peptide Ags or with autologous PBMC infected with a canarypox viral vector encoding the total pp65 protein (ALVAC-pp65). Subsequent immunomagnetic purification of newly CD25-expressing cells allowed efficient recovery of T lymphocytes specific for the initial stimuli, i.e., for the already known immunodominant epitope corresponding to the peptides used as a model or for newly defined epitopes corresponding to peptides encoded by the transfected pp65 protein. Importantly, we demonstrated that direct PBMC stimulation allowed recovery not only of CD8(+) memory T lymphocytes, but also of the CD4(+) memory T cells, which are known to be crucial to ensure persistence of adoptively transferred immune memory. Finally, our analysis of pp65-specific T cells led to the identification of several new helper and cytotoxic epitopes. This work thus demonstrates the feasibility of isolating memory T lymphocytes specific for a clinically relevant protein without the need to prepare APC, to use infectious viral strains, or to identify immunodominant epitopes.
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PMID:Purification of Ag-specific T lymphocytes after direct peripheral blood mononuclear cell stimulation followed by CD25 selection. I. Application to CD4(+) or CD8(+) cytomegalovirus phosphoprotein pp65 epitope determination. 1159 40


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