Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The site on influenza virus N9 neuraminidase recognized by NC41 monoclonal antibody comprises 19 amino acid residues that are in direct contact with 17 residues on the antibody. Single sequence changes in some of the neuraminidase residues in the site markedly reduce antibody binding. However, two mutants have been found within the site, Ile368 to Arg and Asn329 to Asp selected by antibodies other than NC41, and these mutants bind NC41 antibody with only slightly reduced affinity. The three-dimensional structures of the two mutant N9-NC41 antibody complexes as derived from the wild-type complex are presented. Both structures show that some amino acid substitutions can be accommodated within an antigen-antibody interface by local structural rearrangements around the mutation site. In the Ile368 to Arg mutant complex, the side-chain of Arg368 is shifted by 2.9 A from its position in the uncomplexed mutant and a shift of 1.3 A in the position of the light chain residue HisL55 with respect to the wild-type complex is also observed. In the other mutant, the side-chain of Asp329 appears rotated by 150 degrees around C alpha-C beta with respect to the uncomplexed mutant, so that the carboxylate group is moved to the periphery of the antigen-antibody interface. The results provide a basis for understanding some of the potential structural effects of somatic hypermutation on antigen-antibody binding in those cases where the mutation in the antibody occurs at antigen-contacting residues, and demonstrate again the importance of structural context in evaluating the effect of amino acid substitutions on protein structure and function.
J Mol Biol 1992 Sep 05
PMID:Crystal structures of two mutant neuraminidase-antibody complexes with amino acid substitutions in the interface. 152 84

The membrane M-protein of Newcastle disease virus is localized directly beneath the lipid bilayer. Although this protein is the major constituent of the virus, its structural relationship to the lipid or to the other viral component hemagglutinin-neuraminidase, the so called HN-glycoprotein, is still unknown. The effects of either M-protein alone or both M-protein and HN-glycoprotein on the lipid assemblies in reconstituted liposomes were determined by differential polarized phase fluorometry, steady-state fluorescence anisotropy and emission lifetime measurements. It is demonstrated that the degree of rotation of fluorophores in reconstituted liposomes is restricted by the molecular packing of lipids in the bilayer and this in turn can be correlated with the structural order of the lipids in the membrane. The experimental results show that the structural order parameters calculated from the fluorescence measurements are strongly influenced by the presence of both M-protein and HN-glycoprotein in the lipid assemblies.
Mol Biol Rep 1992 Feb
PMID:Effects of the components of Newcastle disease virus on the structural order of lipid assemblies. 154 82

The endoplasmic reticulum (ER)-localized chaperone protein, GRP78-BiP, is involved in the folding and oligomerization of secreted and membrane proteins, including the simian virus 5 hemagglutinin-neuraminidase (HN) glycoprotein. To understand this interaction better, we have constructed a series of HN mutants in which specific portions of the extracytoplasmic domain have been deleted. Analysis of these mutant polypeptides expressed in CV-1 cells have indicated that GRP78-BiP binds to selective sequences in HN and that there exists more than a single site of interaction. Mutant polypeptides have been characterized that are competent and incompetent for association with GRP78-BiP. These mutants have been used to show that the induction of GRP78-BiP synthesis due to the presence of nonnative protein molecules in the ER is dependent on GRP78-BiP complex formation with its substrates. These studies have implications for the function of the GRP78-BiP protein and the mechanism by which the gene is regulated.
Mol Biol Cell 1992 Feb
PMID:Analysis in vivo of GRP78-BiP/substrate interactions and their role in induction of the GRP78-BiP gene. 155 Sep 58

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.
Mol Microbiol 1992 Apr
PMID:Cloning, sequencing and distribution of the Salmonella typhimurium LT2 sialidase gene, nanH, provides evidence for interspecies gene transfer. 160 67

Single crystals of neuraminidase from the bacterium Micromonospora viridifaciens were obtained using the hanging drop vapour diffusion method and polyethylene glycol as precipitant at pH 5.0 or 5.5. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell dimensions a = 48.14 A, b = 82.73 A, c = 84.75 A and with one molecule in the asymmetric unit. Diffraction extends to at least 1.7 A.
J Mol Biol 1992 Jun 20
PMID:Crystallization and preliminary crystallographic study of neuraminidase from Micromonospora viridifaciens. 161 96

A high affinity binding site for [3H]dihydrotetrabenazine is thought to be present on the monoamine transport protein from chromaffin granules. We describe a procedure for purification of this binding activity from frozen bovine adrenal tissue, and we partially characterize the purified preparation. Binding activity solubilized with sodium cholate and soybean lecithin was fractionated on wheat germ lectin-Sepharose, phenyl-Sepharose, Mono Q, and hydroxylapatite. Denaturing electrophoresis of the purified binding activity, followed by silver staining, revealed a single broad band centered at an apparent molecular weight of 85,000. This preparation bound [3H]dihydrotetrabenazine with an apparent dissociation constant of 2.7 nM and had a site density of 10 nmol/mg. Treatment of the purified protein with neuraminidase reduced the apparent molecular weight by 9000, indicating the presence of terminal sialic acids on the oligosaccharide portion of this molecule.
Mol Pharmacol 1991 Dec
PMID:Purification of a [3H]dihydrotetrabenazine-binding protein from bovine adrenal medulla. 166 39

Brevetoxin, a neurotoxin isolated from the marine dinoflagellate Ptychodiscus brevis, has been derivatized into a photoaffinity probe by carbodiimide linkage to p-azidobenzoic acid. Rosenthal analysis of a tritiated p-azidobenzoate brevetoxin derivative indicates that specific binding of the toxin occurs at two distinct and separate sites, with Kd and Bmax values of 0.21 nM and 2.12 pmol/mg of protein for the high affinity site and 50.7 nM and 91.5 pmol/mg of protein for the low affinity site, respectively. Binding of tritiated photoaffinity probe to the high affinity/low capacity site can be displaced in a competitive manner by native brevetoxin (Kd = 1.9 nM), demonstrating a specific competitive interaction with the receptor site. Rat brain synaptosomes, covalently labeled with the brevetoxin photoaffinity probe, were subjected to detergent solubilization. The covalently labeled membrane protein was estimated to have a Stokes radius of 55 +/- 3 A. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed specific labeling of a 260-kDa protein. Treatment with 2-mercaptoethanol and neuraminidase resulted in retention of brevetoxin binding to this high molecular weight protein. The affinity-purified membrane protein-brevetoxin photoaffinity probe complex was specifically recognized by a sodium channel antibody directed against the intracellular side of transmembrane segment IS6. The sodium channel alpha subunit is implicated as the specific site of brevetoxin interaction.
Mol Pharmacol 1991 Dec
PMID:Photoaffinity labeling of the brevetoxin receptor on sodium channels in rat brain synaptosomes. 166 42

Normal and malignant myeloids cells are known to express cell surface molecules having in common the carbohydrate antigen lacto-N-fucopentaose-III (LNF-III--termed CD15). We used flow cytometry to examine the variability of CD15 expression in normal cells and acute myeloid leukemia (AML) cells as detected by 24 murine monoclonal antibodies (mAb). Important differences in the levels of binding were observed with the various mAb. Titrations of each mAb were performed to confirm that these differences in binding were due to increased antigen detection and not differences in concn. In studies of CD15 expression on AML cells selected from a large prospective study, anti-CD15-1 (also known as PM-81) showed the highest binding to each case. Neuraminidase was added to cells from seven AML patients that we had previously found to be low in CD15 expression, in order to determine if cryptic CD15 was present on these cells. Neuraminidase enhanced binding of each of the entire panel of mAb on five patients' cells, thus demonstrating the ubiquitous expression of CD15 on AML cells. In two cases, binding of only some of the mAb was increased, indicating exposure of unusual epitopes on those cells. Subpopulations of normal peripheral blood lymphocytes, cells not associated with CD15 expression, also substantially increased their level of binding to some of the mAb after the addition of neuraminidase. Two-color flow cytometry was used to determine the immunologic phenotype of the lymphocytic population that expressed CD15. This technique revealed that 9.5% normal lymphocytes coexpressed the CD15 and CD3 (T cell) antigens. In addition, by gating on large granular lymphocytes we found that 24.4% of these cells coexpressed CD15 (detected by PM-81) and CD2 (sheep erythrocyte receptor), while 50.3% expressed CD15 and CD16 (type III Fc receptor, natural killer cell-associated). This is consistent with the notion that sialylated CD15 is expressed on some natural killer cells and T cells.
Mol Immunol 1991 Sep
PMID:Expression of the CD15 antigen on normal and leukemic myeloid cells: effects of neuraminidase and variable detection with a panel of monoclonal antibodies. 168 29

The human choriocarcinoma cell line, BeWo, synthesizes the glycoprotein hormone, human chorionic gonadotropin (hCG). We have undertaken this study to compare the synthesized and secreted forms of hCG and their alpha- and beta-subunits in cell cultures of BeWo cells to those forms of normal placental cells by immunobinding techniques. BeWo cells appeared to synthesize and secrete one species of the respective hCG subunit. The immature alpha- and beta-subunits, synthesized in BeWo cells as well as those of placental cells, were digested by endoglycosidase H indicating N-linked sugar chain(s) to be the high-mannose type. The mature alpha- and beta-subunits, secreted by BeWo cells as well as subunits of urinary hCG which are usually used as a standard hCG secreted by normal placental cells, were sensitive to neuraminidase treatment indicating that these subunits have terminal sialic acid(s). Contrary to placental cells, mature subunits of BeWo hCG could not be found in any subcellular fraction indicating a rapid secretion rate or supporting the hypothesis that BeWo cells secrete hCG subunits without the formation of secretory granules. The alpha-subunit synthesized in BeWo cells had a slightly lower molecular weight than that of placental cells; however, the alpha-subunit secreted by BeWo cells had a slightly higher molecular weight than the alpha-subunit of urinary hCG. The beta-subunits synthesized and secreted by BeWo cells had slightly higher molecular weights than beta-subunits of both placental cells and urinary hCG. Even after digestion by N-glycanase as well as endoglycosidase H, molecular weights were still different between the respective subunits of BeWo and placental cells indicating that the apoprotein structures of BeWo hCG subunits may differ from those of placental cells. Moreover, urinary beta-subunit was sensitive to endo-alpha-N-acetylgalactosaminidase treatment but the beta-subunit secreted by BeWo cells was not, indicating that the structure of O-linked sugar chain(s), if present, may be unusual. Analysis of assembled and free forms of subunits of BeWo cell cultures by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing conditions followed by immunobinding methods revealed that subunits are associated intracellularly and then secreted to the media as hCG. Moreover, only free beta-subunits, but not alpha-subunits, of BeWo hCG were found intra- and extracellularly.
Mol Cell Endocrinol 1990 Mar 05
PMID:Synthesis and secretion of human chorionic gonadotropin and its subunits in choriocarcinoma cells: a comparative study with normal placental cells. 169 20

The role of sialic acid residues in the interactions of muscarinic agonists with the cardiac M2 muscarinic receptor was investigated by competitive binding experiments using the lipophilic radioligand (-)-[benzilic-4,4-3H]quinuclidinyl benzilate ([3H]QNB) and the hydrophilic ligand [N-methyl-3H]scopolamine methyl chloride ([3H]NMS). Direct labeling of the agonist binding sites was performed with the radiolabeled agonist [methyl-3H]oxotremorine M acetate ([3H]oxo-M). Neuraminidase decreased the affinity of the M2-selective agonist carbamylcholine in competitive binding experiments performed with [3H]QNB and [3H]NMS. The binding of the M1-selective agonist (4hydroxy-2-butynyl)trimethylammonium chloride m-chlorocarbanilate (McN-A-343), of the M1-selective antagonist pirenzepine, and of the M2-selective antagonist 11-([2-[(diethylamino)methyl]-1 piperidinyl]acetyl)-5,11-dihydro-6H-pyrido(2,3b)(1,4)benzodiazepin -6-on (AF-DX-116) were not affected by neuraminidase. Neuraminidase did not modify the binding parameters of 3H-antagonists but reduced the number of agonist binding sites revealed by [3H]oxo-M. The removal of sialic acid decreased the half-life of the receptor-agonist complex. The present results suggest that removal of sialic acid reduces the formation of super-high affinity agonist-receptor complexes. Sialic acid may catalyze macroscopic binding by enhancing accumulation of the agonist at the membrane surface.
Mol Pharmacol 1990 May
PMID:Sialic acid residues as catalysts for M2-muscarinic agonist-receptor interactions. 169 6


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