Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: UNIPROT:Q07644 (polypeptide)
72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Salmonella typhimurium LT2 sialidase (neuraminidase, EC 3.2.1.18) structural gene, nanH, has been cloned and sialidase overproduced from multicopy plasmids in Escherichia coli. Sialidase expression was regulated positively by cAMP. In contrast, certain Tn1000 insertions located upstream of nanH coding sequences reduced sialidase activity. A nanH chromosomal insertion mutation constructed by marker exchange demonstrated a single sialidase gene copy in S. typhimurium LT2. The complete nucleotide sequence of nanH, encoding a 41,300 dalton polypeptide, was determined and the derived primary structure was similar to sialidases from Clostridium perfringens, Clostridium sordellii, Bacteroides fragilis, and Trypanosoma cruzi. Comparative sequence analysis, including codon usage and secondary structure predictions, indicated that the S. typhimurium and clostridial sialidases are homologous, strongly suggestive of an interspecies gene transfer event. At least two primary sequence motifs of the bacterial enzymes were detected in influenza A virus sialidases. The predicted secondary structure of the bacterial enzymes was strikingly similar to viral sialidase. From the population distribution of nanH detected within a collection of salmonellae, it was apparent that S. typhimurium obtained its nanH copy most recently from Salmonella arizonae. S. typhimurium LT2 is thus a genetic mosaic that differs from other strains of even the same serotype by nanH plus potentially additional characters linked to nanH. These results have relevance to the evolution and function of sialidases in pathogenic microbes, and to the origin of the sialic acids.
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PMID:Cloning, sequencing and distribution of the Salmonella typhimurium LT2 sialidase gene, nanH, provides evidence for interspecies gene transfer. 160 67

Monoclonal antibody KS1/4 recognizes an epitope expressed on the cell surface of human adenocarcinoma cells and certain epithelia. Western blotting analyses of tumor cell extracts utilizing KS1/4 reveal staining of a major Mr 40,000 band and a minor Mr 42,000 band. Both components are also detectable in KS1/4 immunoprecipitates of L-[35S]methionine- and D-[3H]glucosamine-labeled human lung tumor cell extracts. When synthesis occurs in the presence of tunicamycin or when the immunoprecipitates are treated with peptide:N-glycosidase F, a single polypeptide component (Mr 37,000) is precipitated. Immediately following translation, digestion of Mr 40,000 and Mr 42,000 glycoproteins with endo-beta-N- acetylglucosaminidase H also yields a single polypeptide component at Mr 37,000. However, over a 3-h period beginning at 10 min posttranslation, a Mr 39,000 major component and a Mr 41,000 minor component gradually appear in the endo-beta-N-acetylglucosaminidase H digests as the Mr 37,000 component gradually disappears. Analysis of tryptic glycopeptides derived from the Mr 40,000 and 42,000 components suggests that the two components differ by the addition of one extra oligosaccharide to the Mr 42,000 component. Nonequilibrium pH gradient electrophoresis/sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of KS1/4 immunoprecipitates resolves each of the two components into multiple spots. Digestion of the KS1/4 immunoprecipitates with neuraminidase prior to two-dimensional analysis or immunoprecipitation of short pulse-labeled extracts reduces the number of spots to three each at the Mr 40,000 and Mr 42,000 positions. Digestion of the KS1/4 immunoprecipitates with peptide:N-glycosidase F, immunoprecipitation of extracts labeled in the presence of tunicamycin, or endo-beta-N-acetylglucosaminidase H digestion of immunoprecipitates of short pulse-labeled extracts prior to two-dimensional analysis results in a single series of Mr 37,000 spots, suggesting that the polypeptide portions of the Mr 40,000 and Mr 42,000 components may be identical. Endo-beta-N-acetylglucosaminidase H digestion of KS1/4 immunoprecipitates of short pulse-labeled extracts, followed by nonequilibrium pH gradient electrophoresis, V8 protease digestion, and polyacrylamide gel electrophoresis revealed an apparently identical set of polypeptides derived from each of the three Mr 37,000 spots, suggesting that the three spots derive from highly similar polypeptides.
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PMID:Biosynthesis and glycosylation of the carcinoma-associated antigen recognized by monoclonal antibody KS1/4. 169 23

The neuraminidase (NA) genes of influenza B viruses B/Maryland/59, B/Hong Kong/8/73, B/Singapore/222/79, B/Oregon/5/80, B/USSR/100/83, B/Victoria/3/85, B/Leningrad/179/86, B/Memphis/6/86, and B/Memphis/3/89 have been sequenced. The deduced amino acid sequences show high variability in the stalk domain of the NA, but a surprising degree of sequence conservation in the head region which carries all the antigenic and enzyme activity. The variable region coding for the neuraminidase stalk also translates into a variable section in the overlapping NB polypeptide, which is coded from a second reading frame that overlaps the first 100 amino acids of NA. The influenza B NAs are antigenically distinguishable with monoclonal antibodies in neuraminidase-inhibition tests, even when there is only one amino acid sequence difference. However, seven of nine escape mutants selected with monoclonal antibodies were distinguished only by the antibody used for selection. When NA heads of influenza B viruses are crystallized, there are remarkable differences in crystal morphology between neuraminidases which have very few sequence changes.
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PMID:Antigenic, sequence, and crystal variation in influenza B neuraminidase. 169 10

Evidence is presented that monoclonal antibody BA-1, directed against a marker (CD24) of human lymphocytes of B cell lineage, recognizes a sialic acid-dependent epitope. This conclusion is based on a series of experiments exploiting the reaction of this antibody with bovine and ovine submaxillary mucins. Expression of the epitope was enhanced following alkaline saponification of bovine submaxillary mucin, which converts O-acetylated neuraminic acid residues to N-acetylneuraminic acid. The epitope was destroyed following neuraminidase or mild acid treatment of the mucins, and its expression was diminished following neuraminidase treatment of B lymphoblastoid cells. Glycopeptides obtained by digestion of the bovine mucin with papain, trypsin or pronase were lacking in antigenicity. However, antigenic activity could be regenerated after conjugation of pronase glycopeptides to poly-L-lysine. These results indicate that multivalent display of sialo-oligosaccharide on peptide rather than a protease-susceptible polypeptide domain is required for BA-1 antibody binding.
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PMID:Monoclonal antibody BA-1 to the human B lymphocyte marker CD24 recognizes a sialic acid (N-acetylneuraminic acid) dependent epitope in multi-valent display on peptide. 169 99

Monoclonal antibodies which inhibit influenza virus neuraminidase (NA) and which therefore indirectly neutralize virus infectivity bind to epitopes located on the rim of the active-site crater. The three-dimensional structure of one of these epitopes, recognized by monoclonal antibody NC41, has previously been determined (W. R. Tulip, J. N. Varghese, R. G. Webster, G. M. Air, W. G. Laver, and P. M. Colman, Cold Spring Harbor Symp. Quant. Biol. 54:257-263, 1989). Nineteen escape mutants of influenza virus A/tern/Australia/G70c/75 (N9) NA selected with NC41 were sequenced. A surprising restriction was seen in the sequence changes involved. Ten mutants had a Ser-to-Phe change at amino acid 372, and six others had mutations at position 367. No escape mutants with changes at 369 or 370 were found, although these mutations were selected with other antibodies and rendered the epitope unrecognizable by antibody NC41. Another N9 NA, from A/ruddy turnstone/NJ/85, which differs by 14 amino acids from the tern virus NA, still bound antibody NC41. Epitope mapping by selecting multiple escape mutants with antibody NC41 thus identified only three of the five polypeptide loops on NA that contact the antibody. Escape mutants selected sequentially with three different monoclonal antibodies showed three sequence changes in two loops of the NC41 epitope. The multiple mutants were indistinguishable from wild-type virus by using polyclonal rabbit antiserum in double immunodiffusion tests, but NA inhibition titers were fourfold lower. The results suggest that although the NC41 epitope contains 22 amino acids, only a few of these are so critical to the interaction with antibody that a single sequence change allows selection of an escape mutant. In that case, the variety of amino acid sequence changes which can lead to polyclonal selection of new epidemic viruses during antigenic drift might be very limited.
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PMID:Mechanism of antigenic variation in an individual epitope on influenza virus N9 neuraminidase. 170 Aug 25

Although the myelin-associated glycoprotein (MAG) cannot be detected in primary cultures of rat Schwann cells in the absence of neurons, MAG expression was demonstrated in some lines of cultured Schwann cells that had been immortalized by repetitive passaging. Radioimmunoassay of one such Schwann cell line, S-16, showed a remarkably high MAG concentration of about 1 ng/microgram of total protein, a level that is comparable to the MAG concentration in adult sciatic nerve. The S-16 cells divide very rapidly, are rounder than normal Schwann cells, and elaborate many processes after reaching high density. The cells are galactocerebroside positive, but express little or no P0 glycoprotein or myelin basic protein. As in nerve, the MAG synthesized by the cultured cells is primarily the shorter isoform (S-MAG). Furthermore, the posttranslational processing resembles that occurring in vivo including a similar degree of glycosylation, sulfation of oligosaccharides, and phosphorylation of the polypeptide. The sensitivity of MAG to treatment of the intact cells with trypsin or neuraminidase, as well as surface labeling with [3H]borohydride reduction after periodate oxidation, demonstrated that most of the MAG expressed by the S-16 cells is located on the cell surface. This line of immortalized Schwann cells expressing a remarkably high level of MAG should be useful for investigating the cell biology and function of this glycoprotein.
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PMID:Expression of the myelin-associated glycoprotein in cultures of immortalized Schwann cells. 170 58

Trypanosoma cruzi expresses a developmentally regulated neuraminidase (TCNA) implicated in parasite invasion of cells. We isolated full-length DNA clones encoding TCNA. Sequence analysis demonstrated an open reading frame coding for a polypeptide of 1,162 amino acids. In the N-terminus there is a cysteine-rich domain containing a stretch of 332 amino acids nearly 30% identical to the Clostridium perfringens neuraminidase, three repeat motifs highly conserved in bacterial and viral neuraminidases, and two segments with similarity to the YWTD repeats found in the low density lipoprotein (LDL) receptor and in other vertebrate and invertebrate proteins. This domain is connected by a structure characteristic of type III modules of fibronectin to a long terminal repeat (LTR) consisting of 44 full length copies of twelve amino acids rich (75%) in serine, threonine, and proline. LTR is unusual in that it contains at least 117 potential phosphorylation sites. At the extreme C-terminus is a hydrophobic segment of 35 amino acids, which could mediate anchorage of TCNA to membranes via a glycosylphosphatidylinositol linkage. This is the first time a protozoan protein has been found to contain a YWTD repeat and a fibronectin type III module. The domain structure of TCNA suggests that the enzyme may have functions additional to its catalytic activity such as in protein-protein interaction, which could play a role in T. cruzi binding to host cells.
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PMID:The Trypanosoma cruzi neuraminidase contains sequences similar to bacterial neuraminidases, YWTD repeats of the low density lipoprotein receptor, and type III modules of fibronectin. 171 61

Eleven monoclonal antibodies were identified that recognized eel electroplax sodium channels. All the monoclonal antibodies specifically immunostained the mature TTX-sensitive sodium channel (Mr 265,000) on immunoblots. None of the monoclonal antibodies would precipitate the in vitro translated channel core polypeptide in solution. One monoclonal antibody, 3G4, was found to bind to an epitope involving terminal polysialic acids. Extensive digestion of the channel by the exosialidase, neuraminidase, or partial polysialic acid removal by the endosialidase, endo-N-acetylneuraminidase, destroy the 3G4 epitope. 3G4 is, therefore, a highly selective probe for the post-translationally attached polysialic acids. Except for this monoclonal antibody, the epitopes recognized by the remaining antibodies were highly resistant to extensive N-linked deglycosylation. Thus, the monoclonal antibodies may be directed against unique post-translationally produced domains of the electroplax sodium channel, presumably sugar groups that are abundant on this protein (Miller, J.A., Agnew, W.S., Levinson, S.R. 1983, Biochemistry 22:462-470). These monoclonal antibodies should prove useful as tools to study discrete post-translational processing events in sodium channel biosynthesis.
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PMID:Monoclonal antibodies raised against post-translational domains of the electroplax sodium channel. 171 74

K1 is a monoclonal antibody that reacts with a cell surface antigen (CAK1) found in human mesothelia and nonmucinous ovarian tumors. In this article, the characteristics of the CAK1 antigen have been examined in detail. Using immunofluorescence microscopy, we have found that the CAK1 signal is removed from the cell surface by treatment with proteases or by phosphatidylinositol-phospholipase C, but not by neuraminidase and beta-galactosidase. The phosphatidylinositol-phospholipase C-released material was found to contain the CAK1 antigen which was detected by a competition radioimmunoassay. The phosphatidylinositol-phospholipase C-released CAK1 antigen was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting and found to be approximately 40 kDa protein. The CAK1-K1 antibody complex remains on the cell surface and is poorly internalized, as shown by an acid wash immunofluorescence internalization assay. An immunotoxin composed of K1 and Lys-PE40, a mutant form of Pseudomonas exotoxin lacking the cell binding domain, was not cytotoxic, supporting the conclusion that the CAK1-K1 antibody complex is not internalized. However, an immunotoxin composed of K1 and native Pseudomonas exotoxin was selectively cytotoxic to cells expressing the CAK1 antigen. This cytotoxicity is due to the fact that domain I of Pseudomonas exotoxin promotes internalization of antigens which are not internalized or bound to antibody alone. Our results suggest that CAK1 is a polypeptide that is expressed on mesothelial cells and many ovarian cancers, and that K1 may be useful as a targeting agent for the immunotherapy of human ovarian cancer.
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PMID:Characterization of the antigen (CAK1) recognized by monoclonal antibody K1 present on ovarian cancers and normal mesothelium. 172 78

It has previously been shown that influenza virus neuraminidase (NA) of the N9 subtype is unusual in that it possesses hemagglutinin activity as well as NA activity. Loss of red cell binding in certain escape mutants suggested that the hemagglutinating site is separate from the NA active site and involves at least two of the polypeptide loops found on the surface of the molecule (Webster et al., 1987. J. Virol. 61, 2910-2916). We have used site-directed mutagenesis to transfer the amino acids in these loops at positions 368-370 and 399-403 of N9 NA (A/tern/Australia/G70c/75), separately and together, into subtype N2 NA (A/Tokyo/3/67). The three mutant proteins were expressed from an SV40 transient expression system (Fuerst et al., 1986. Proc. Natl. Acad. Sci. USA. 83, 8122-8126). The mutant which contained both loops of N9 NA had acquired the hemagglutinin activity of N9. The agglutinated red cells are released by the enzyme activity of N9 NA, indicating that the agglutination involves binding to sialic acid in the same configuration as does the parental N9 NA, and an inhibitor of NA did not affect hemagglutination, indicating that this site is separate from the NA site as in parental N9.
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PMID:Transfer of the hemagglutinin activity of influenza virus neuraminidase subtype N9 into an N2 neuraminidase background. 185 57


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