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)

gamma-Hydroxybutyric acid (GHB) is a natural compound of mammalian brain synthesized from GABA. The characteristics of its synthesis, transport, release, distribution and turnover, in addition to the presence of a high affinity binding site for this substance in brain are in favor of a modulator role for GHB. The effects of hydrolytic enzymes on the specific binding capacity of GHB have been studied in the present work. Phospholipases A2 and C, neuraminidase and Pronase markedly decrease GHB binding to crude synaptosomal membranes from rat brain. This effect is time and enzyme concentration dependent. Trypsin, under the conditions employed, is less active. The inhibitory effects of phospholipases is correlated with phospholipid hydrolysis. Lysophospholipids, in the absence of bovine fatty acid free serum albumin partially inhibit GHB binding. The action of neuraminidase has been followed by sialic acid release and modifications of the ganglioside profile. The effects of phospholipase C and of neuraminidase are completely different to those on GABA binding sites. These results represent further data concerning the molecular existence of specific GHB binding sites on rat brain membranes.
Mol Cell Biochem 1990 Mar 05
PMID:Effects of phospholipases, proteases and neuraminidase on gamma-hydroxybutyrate binding sites. 218 47

We used the whole-cell configuration of the patch-clamp technique and cultured ventricular myocytes from 7-day embryonic chicks to test the hypothesis that sialic acid residues (NANA) constitute the negative surface charge associated with delayed rectifier potassium channels. Delayed rectifier current (iK) was elicited at potentials between -40 and +60 mV. The existence of negative fixed charges close to the "gating sensor" was confirmed by a 6.8-mV negative shift of the half-activation potential (V1/2) following a 10-fold reduction of divalent cations and a 22.6-mV position shift following the addition of 10 mM NiCl2. An 8.4-mV increase in the Boltzmann equation slope factor (k) in the former experiment and a 5.5-mV decline in the latter suggested that the surface charge is not uniformly distributed. We used a high performance liquid chromatography procedure to detect freed sarcolemmal NANA and found that 71-88% was released by neuraminidase (0.2-2.0 U/ml) during 1-h treatments. Such treatments had no significant effect upon the amplitudes of iK or V1/2. On the other hand, k was increased significantly by the enzyme (2.0 U/ml), but only when Ca2+ was present. Finally, 1-h pre-treatments with neuraminidase (2.0 U/ml) had no effect on the positive shift of V1/2 induced by Ni2+. We conclude that although sarcolemmal NANA may bind Ca2+, it does not constitute the surface charge of delayed rectifier potassium channels.
J Mol Cell Cardiol 1990 Nov
PMID:Sialic acid and the surface charge of delayed rectifier potassium channels. 228 87

Cell surface forms of Qa-6 class I molecules are biochemically indistinguishable from Qa-2 although Qa-6 maps telomeric to Qa-2 with the recombinant strain B6.K2. Analysis of appropriate F1 strains did not demonstrate the presence of a trans acting factor that could modify the Qa-2 molecule to produce the Qa-6 determinant. Also, neither a neighboring cell surface molecule nor oligosaccharides were found to block the recognition of the Qa-6 determinant in Qa-2+,6- strains. The 2-D gel profiles of neuraminidase or endoglycosidase treated anti-Qa-2 immunoprecipitates from lysates of cell surface iodinated Qa-2+,6+ strains revealed an additional basic polypeptide which was absent from that of Qa-2+,6- strains. Thus, differential sialylation/glycosylation of Qa-2 molecules masks detection of Qa-2 antigen heterogeneity when cell surface forms are analyzed. Qa-6+ phenotype associated polypeptides were also found at various stages of post-translational processing in cells metabolically labeled in the presence and absence of tunicamycin. Northern analyses using Q7 and Q9 specific oligonucleotide probes revealed appropriate sized transcripts for both genes in the Qa-2+,6+ strain B6 but only Q9 in the Qa-2+,6- strain B6.K2. These data demonstrate that there is structural heterogeneity in Qa-2 antigens expressed by Qa-2+,6+ and Qa-2+,6- strains which results from differential expression of the Q7 and Q9 genes.
Mol Immunol 1990 Jun
PMID:Biochemical differences in Qa-2 antigens expressed by Qa-2+,6+ and Qa-2+,6- strains. Evidence for differential expression of the Q7 and Q9 genes. 238 28

Mammalian A2-adenosine receptor binding subunits (A2AR) can be visualized by covalent labeling with the photoaffinity crosslinking ligand 125I-2-[4-[2-[2-[(4-aminophenyl)methylcarbonylamino] ethylaminocarbonyl]ethyl]phenyl]ethylamino-5'-N-ethylcarboxamidoad enosine or directly with the azide derivative described in this paper. The protein comprising the A2-adenosine receptor binding subunit migrates with a Mr of 45,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In this study, the glycoproteins representing the radiolabeled A1- and A2-adenosine receptor binding subunit from bovine brain were compared by partial peptide maps and following treatment with exo- and endoglycosidases. Peptide maps using two separate proteases reveal that the A1- and A2-adenosine receptor binding subunits share no common peptide fragments by two-dimensional gel electrophoresis. Endoglycosidase F treatment of labeled A2AR results in a single labeled peptide of Mr 38,000 without intermediate peptides, suggesting a single N-linked carbohydrate chain. The labeled A2AR demonstrates a sensitivity to neuraminidase, as evidenced by an increased mobility on gel electrophoresis, suggesting the receptors contain a glycan component containing terminal sialic acid. Treatment of the labeled A2AR with alpha-mannosidase reveals two distinct populations of A2ARs, one of which is sensitive and the other resistant to the enzyme. The nonadditivity of sequential treatments with the two exoglycosidases suggests, a heterogeneous population of A2AR containing either complex- or high mannose-type carbohydrate chains. These data suggest the A2AR is a Mr 45,000 glycoprotein with a single carbohydrate chain of either the complex or high mannose type. In addition, the A1- and A2ARs are distinct glycoproteins, as evidenced by their differing molecular weights (before and after deglycosylation) and distinct peptide maps.
Mol Pharmacol 1990 Aug
PMID:Glycoprotein nature of the A2-adenosine receptor binding subunit. 238 30

New crystalline forms of tetrameric neuraminidase heads from two strains (B/Lee/40 and B/mem/89) of type B human influenza virus were obtained and the crystals diffracted using X-rays to 2.5 A resolution without lattice disorder. The new B/Lee/40 crystalline form is tetragonal, space group P42(1)2, with unit cell dimensions a = 123.8 A, c = 71.8 A. The B/mem/89 crystalline form is also tetragonal, space group I422, with unit cell dimensions a = 122.9 A, c = 164.4 A. There is one neuraminidase monomer per asymmetric unit in both forms.
J Mol Biol 1990 Aug 05
PMID:New crystalline forms of neuraminidase of type B human influenza virus. 238 63

Rhoptry proteins of Plasmodium falciparum merozoites, of 140, 130, and 110 kDa, identified by co-precipitation with Mab.1B9, bind selectively to mouse erythrocytes and reticulocytes. The properties of binding are shown to correlate with invasion of P. falciparum into mouse erythrocytes. Invasion of two strains of P. falciparum 7G8 and FCR-3, into mouse erythrocytes was examined, and was found to differ significantly. The 7G8 strain invades mouse erythrocytes at a rate of 40-60% compared to invasion into human erythrocytes, whereas FCR-3 invades at a rate of 5-15%. Both strains of P. falciparum preferentially invade reticulocytes in the in vitro invasion assay. This correlated with an increase in the amount of rhoptry protein of the 7G8 strain bound to mouse erythrocytes, compared to the FCR-3 strain and an increased binding to reticulocytes compared to mature erythrocytes. Binding of the rhoptry proteins and merozoite invasion into the erythrocyte is blocked in erythrocytes treated with trypsin and chymotrypsin but not in neuraminidase-treated erythrocytes, suggesting that the putative receptor site is exposed and accessible on the erythrocyte surface. Rabbit antiserum against gp3, the major glycophorin of mouse erythrocytes, blocks binding of the rhoptry proteins to erythrocytes and reduces merozoite invasion into mouse erythrocytes by 50%. Binding of rhoptry proteins to mouse reticulocytes was not blocked by alpha gp3 indicating a receptor difference between reticulocytes and erythrocytes. Mab.1B9 reduces merozoite invasion but does not decrease binding of the rhoptry proteins to the mouse erythrocyte. The mouse erythrocyte serves as a useful model to study the receptor-ligand interaction of rhoptry proteins and host surface proteins and to define the role of the rhoptry proteins during the invasion process.
Mol Biochem Parasitol 1990 Feb
PMID:Binding of Plasmodium falciparum rhoptry proteins to mouse erythrocytes and their possible role in invasion. 240 96

Sialo- and asialoglycoconjugates were isolated from Trypanosoma cruzi epimastigotes and their composition determined. Sialoglycoconjugates bound to wheat germ agglutinin (WGA)-Sepharose and were precipitated by concanavalin A, Wistaria floribunda hemagglutinin and WGA. Asialoglycoconjugate bound to concanavalin A-Sepharose and precipitated with concanavalin-A and W. floribunda hemagglutinin but not with WGA. Cells grown in the presence of fetal calf serum were agglutinated by WGA but not by peanut agglutinin. The reverse was true for cells grown without fetal calf serum. Neuraminidase-treated cells incorporated sialic acid or its 7-carbon analog, 5-acetamido-3,5-dideoxy-L-arabino-2-heptulosonic acid (AcNeu7) from sialylated compounds such as fetuin or sialyl-lactose but did not incorporate free sialic acid. Restoration of the WGA sialylreceptors in neuraminidase-treated cells, as determined by cell agglutination with WGA, was also obtained by incubation with fetuin or sialyl-lactose but not with free sialic acid. Moreover, restoration of agglutinability by WGA in neuraminidase-treated cells or cells grown in medium without fetal calf serum occurred equally well in energy-rich or energy-depleted cells. A transglycosilase reaction for sialic acid incorporation in T. cruzi epimastigotes is suggested.
Mol Biochem Parasitol 1985 Jun
PMID:Incorporation of sialic acid into Trypanosoma cruzi macromolecules. A proposal for a new metabolic route. 241 16

Guinea pig erythrocytes desialated by treatment with neuraminidase from Vibrio cholerae were lyzed in autologous serum through a natural-antibody-dependent activation of the classical complement pathway. Lysis was inhibited when a mannose, glucose, galactose or N-acetyl-glucosamine was added to the incubation mixture. Methyl-alpha- or -beta-D-galactopyranosides were poorly effective and N-acetyl-D-galactosamine was not effective at all. Inhibition of lysis by the carbohydrates was due neither to an anti-complementary effect nor to a modification of the osmotic pressure since: (a) they did not alter the total complement haemolytic activity of guinea pig serum, and (b) they did not inhibit lysis of desialated guinea pig erythrocytes in human serum through activation of the alternative complement pathway. The presence of mannose, glucose, galactose or N-acetyl-glucosamine in the incubation mixture resulted in an impaired fixation of natural auto-antibodies on antigenic sites, namely the T-antigen (Thomsen-Friedenreich), which were unmasked following membrane sialic acid removal. When tested under the same conditions, only small percentage of the normal human population showed the phenomenon of lysis of desialated erythrocytes in autologous serum. Lysis was not due to a particular susceptibility of erythrocytes from these individuals to complement-mediated lysis but to the presence in their serum of complement-activating anti-T antibodies. As expected, the activity of human anti-T antibodies was inhibited by galactose and N-acetyl-galactosamine, which are the immunodominant sugars of the human T-antigen. Mannose and glucose had no effect, and methyl- alpha- or - beta-D-galactopyranosides were almost as effective as galactose. The heterogeneity of the human population with regard to the complement-activating capacity of anti-T antibodies could be of significance for the individual response of the host to an infection by a neuraminidase-producing microorganism. That the immunodominant sugars of the T-antigen were different between humans and guinea pigs was further assessed by absorption experiments. We have demonstrated that guinea pig anti-T antibodies were not removed during contact with desialated human red cells which do not have the mannose specificity, whereas human antibodies were almost entirely retained on desialated guinea pig red cells which, beside mannose, express galactose. These results also suggest that guinea pig antibodies are mostly directed towards mannose and glucose.
Mol Immunol 1985 Sep
PMID:Differences in carbohydrate specificities and complement-activating capacity of guinea pig and human antibodies to neuraminidase-treated autologous erythrocytes. 241 14

The nature of amino acid replacements in 16 drift variants of hemagglutinin H3 subtype and 5 drift variants of neuraminidase N2 subtype of the influenza A virus were studied. The dependences of relative replacement frequencies and relative quantities of frequent replacements upon differences of properties of substituted residues are plotted. In contrast to most of the known proteins, amino acid replacements in hemagglutinin and neuraminidase depend weakly on the physico-chemical parameters of amino acids. For the antigenic determinants studied the replacement frequencies were compared to those calculated according to two models: one for conservative replacements and the other for accidental mutation of the genetic code. The differences in the nature of amino acid replacements are found in four antigenic determinants of hemagglutinin. The replacements in experimentally selected proteins are shown to go beyond limitations of natural variants. The explanations of the reasons of low epidemicity of some strains and ineffective attempt to imitate the natural antigenic drift of viruses by using experimental selection are proposed. The causes of time-limited circulation of H3N2 influenza virus subtype are discussed.
Mol Biol (Mosk)
PMID:[The nature of amino acid substitution in antigenic drift of hemagglutinin N3 and neuraminidase N2 from the influenza virus]. 242 40

Various strains, stocks, and clones of Trypanosoma cruzi were analyzed for neuraminidase (NA) activity using fetuin and human erythrocytes as substrate. In all cases the activity was found to be developmentally regulated. Zymodeme type I strains, which are histotropic for skeletal muscle, had greater NA activity than zymodeme type II strains which are histotropic for either macrophages or cardiac muscle cells. Heterogeneity of NA expression within strains is suggested by the finding that one Silvio X10 clone had greater NA activity than another clone of the same stock. The differences observed were more pronounced when human erythrocytes and not fetuin were used as substrate. Trypomastigotes of the high producing strains reared in bovine artery smooth muscle cells had enhanced expression compared to trypomastigotes reared in 3T3 or human fibroblast cells. The first harvest of trypomastigotes from cell cultures had greater NA activity than trypomastigotes harvested on subsequent days.
Mol Biochem Parasitol 1986 Aug
PMID:Heterogeneous distribution of neuraminidase activity in strains and clones of Trypanosoma cruzi and its possible association with parasite myotropism. 242 47


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