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: EC:3.2.1.17 (lysozyme)
21,489 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The binding of 125I-labelled egg-white lysozyme to isolated brush border membranes of rat kidney cortex was investigated. The lysozyme binding was reversible and saturable. The Scatchard plot revealed a one-component binding type with a dissociation constant of 7.8 microM and 15.6 nmol/mg membrane protein for the number of binding sites. The binding of the basic lysozyme could be reduced by basic amino acids such as L-lysine, L-ornithine or L-arginine, while neutral amino acids such as L-citrulline or L-alanine had no effect. The inhibitory effect of lysine was competitive.
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PMID:Binding of lysozyme to brush border membranes of rat kidney. 687 Dec 5

Light microscopy and transmission electron microscopy of thin sections and metal-shadowed specimens showed that the sheath of Leptothrix discophora SP-6 (ATCC 51168) is a tube-like extracellular polymeric structure consisting of a condensed fabric of 6.5-nm-diameter fibrils underlying a more diffuse outer capsular layer. In thin sections, outer membrane bridges seen to contact the inner sheath layer suggested that the sheath fabric was attached to the outer layer of the gram-negative cell wall. The capsular polymers showed an affinity for cationic colloidal iron and polycationic ferritin, indicating that they carry a negative charge. Cell-free sheaths were isolated by treatment with a mixture of lysozyme, EDTA, and N-lauroylsarcosine (Sarkosyl) or sodium dodecyl sulfate (SDS). Both Sarkosyl- and SDS-isolated sheaths were indistinguishable in microscopic appearance. However, the Mn-oxidizing activity of Sarkosyl-isolated sheaths was more stable than that of SDS-isolated sheaths. The Sarkosyl-isolated sheaths also contained more 2-keto-3-deoxyoctanoic acid and more outer membrane protein than SDS-isolated sheaths. The oven-dried mass of detergent-isolated sheaths represented approximately 9% of the total oven-dried biomass of SP-6 cultures; the oven-dried sheaths contained 38% C, 6.9% N, 6% H, and 2.1% S and approximately 34 to 35% carbohydrate (polysaccharide), 23 to 25% protein, 8% lipid, and 4% inorganic ash. Gas-liquid chromatography showed that the polysaccharide was an approximately 1:1 mixture of uronic acids (glucuronic, galacturonic, and mannuronic acids and at least one other unidentified uronic acid) and an amino sugar (galactosamine). Neutral sugars were not detected. Amino acid analysis showed that sheath proteins were enriched in cysteine (6 mol%). The cysteine residues in the sheath proteins probably provide sulfhydryls for disulfide bonds that play an important role in maintaining the structural integrity of the sheath (D. Emerson and W.C. Ghiorse, J. Bacteriol. 175:7819-7827, 1993).
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PMID:Ultrastructure and chemical composition of the sheath of Leptothrix discophora SP-6. 750 63

The effect of abundance and compartmentalization of antigenic epitopes expressed in Escherichia coli on phagocytic processing was studied by expressing fusion proteins containing the epitope from positions 52 to 61 of hen egg white lysozyme [HEL(52-61)], which binds the I-Ak murine major histocompatibility complex class II (MHC-II) molecule or the epitope from positions 257 to 264 of chicken egg ovalbumin [OVA(257-264]), which binds the Kb murine MHC-I molecule. Epitopes expressed as fusion proteins in the outer membrane protein LamB allowed exposure of the epitopes either at the bacterial surface, in the periplasmic space, or in the cytoplasm. Regardless of epitope compartmentalization within the bacterium, MHC-II-restricted or MHC-I-restricted presentation to T hybridoma cells occurred after macrophages phagocytosed bacteria producing the HEL(52-61) epitope or the OVA(257-264) epitope, respectively. Increased epitope abundance within a given microbial compartment resulted in increased processing and presentation to epitope-specific T hybridoma cells. Minor differences in the efficiency of epitope processing between the constructs was observed, and the HEL or OVA epitope exposed in the periplasmic space was processed most efficiently compared with the surface- or cytoplasm-localized epitopes. These differences could be overcome by increasing the amount of epitope per bacterium as little as two to five times. The minor differences in processing efficiency may be due to differing protein contexts of the epitope as well as differing epitope compartmentalizations within the bacteria. Thus, production of abundant epitope is the important parameter influencing processing of epitopes expressed in E. coli to induce T-cell responses rather than targeting of an epitope to a specific bacterial compartment.
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PMID:Compartmentalization of defined epitopes expressed in Escherichia coli has only a minor influence on efficiency of phagocytic processing for presentation by class I and class II major histocompatibility complex molecules to T cells. 769 56

The asialoglycoprotein (ASGP) receptor undergoes constitutive endocytosis in HepG2 cells, which is regulated by tyrosine kinase activity (Fallon, R. J., Danaher, M., Saylors, R. L., and Saxena, A. (1994) J. Biol. Chem. 269, 11011-11017). In this study we show that the receptor copurifies with a tyrosine kinase activity, as defined by tyrosine phosphorylation of an exogenous substrate (reduced carboxyamidomethylated and maleylated lysozyme). Analysis of cells transfected with one subunit of the ASGP receptor showed that signals in the cytoplasmic domain of the H1 subunit are sufficient for receptor kinase association. In addition, receptor kinase association is not dependent on the single cytoplasmic tyrosine at position 5. Analysis of the components of anti-ASGP receptor immunoprecipitates revealed the presence of a 127-kDa protein (p127), which becomes phosphorylated on tyrosine upon addition of gamma-[32P]ATP and which is capable of binding ATP.p127 was also demonstrated in anti-transferrin receptor immunoprecipitates but not in immunoprecipitates of a resident membrane protein, human HLA. In conclusion, these data demonstrate that the ASGP receptor, a protein that participates in constitutive, rapid endocytosis, is associated with a cellular tyrosine kinase.
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PMID:The asialoglycoprotein receptor is associated with a tyrosine kinase in HepG2 cells. 792 94

A rapid and simple method for separating and isolating the inner and outer membranes of Escherichia coli is described. Membrane vesicles were prepared either by passing the bacteria through a French press or by conversion of the cells to spheroplasts by the lysozyme-EDTA treatment and disruption of the spheroplasts by sonication. The membrane vesicles were collected by ultracentrifugation and suspended in a Percoll-containing buffer. The membranes were separated by centrifugation of the membrane-Percoll mixture in a fixed angle rotor at 27,000gmax for 30 min in a preparative centrifuge. One low-density and one high-density band was obtained, corresponding to the inner and outer membranes, respectively. For the membranes prepared by French pressing 69 and 3.3% of the total activity in the gradient of the inner membrane marker NADH-oxidase was found in the low-density and the high-density bands, respectively. For the outer membrane marker 2-keto-3-deoxyoctonate (KDO), 69 and 7.3% of the total amount of KDO in the gradient was found in the high-density and the low-density bands, respectively. For the membranes prepared by sonication of spheroplasts the same figures were 39 and 6.5% for NADH-oxidase and 52 and 9.0% for KDO. The total time of preparation of membrane vesicles, from harvesting the bacteria to the separation of the inner and outer membrane vesicles, is about 6 h. A good separation of the inner and outer membranes was still obtained when samples corresponding to about 10 mg of membrane protein were added to a 33-ml gradient.
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PMID:Separation of inner and outer membrane vesicles from Escherichia coli in self-generating Percoll gradients. 813 65

The study addressed the general problem of fractionating cell envelopes in order to isolate the outer membranes of gram-negative bacteria. Whereas the cells are normally transformed into spheroplasts prior to disintegration and membrane separation, Serratia marcescens was found to be resistant to spheroplast formation using the procedures available, which were originally developed for Escherichia coli. An efficient technique for spheroplasting S. marcescens was therefore developed; this comprised combining osmotic shock and lysozyme-EDTA treatment of sucrose-conditioned cells. Spheroplasting efficiency and the amount of outer membrane protein recovered were highly dependent on the spheroplasting technique used. Separation of the outer and inner membranes was performed by two methods, isopyenic centrifugation and selective detergent solubilization with Sarkosyl. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and the analysis of specific inner membrane marker enzymes revealed that the protein obtained by detergent solubilization was much purer than that obtained by isopycnic centrifugation. The outer membrane isolated accounted for 60% of the envelope proteins and had a buoyant density of 1.2502 g/cm3. The protein profile of the outer membrane determined by SDS-PAGE resolved into 12 distinct protein bands, 3 of which represented major proteins.
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PMID:Isolation and characterization of the outer membrane proteins of Serratia marcescens W225. 825 Feb 25

The product encoded by the latent membrane protein (LMP) gene of Epstein-Barr virus (EBV) has been implicated as a transforming protein by a number of studies. We have examined the effects of LMP expression in FDCP-mix cells, a growth factor-dependent multipotential murine 'stem cell' line. Our studies show that LMP reduces the generation of clonogenic cells and leads to the production of cells expressing a marker (lysozyme M) characteristic of mature monocytes and macrophages. Furthermore, cells expressing LMP are compromised in their ability to produce mature neutrophils. These data suggest that expression of LMP in primitive cells can modulate their self-renewal and differentiation potential and provide evidence in support of the suggestion that EBV may be involved in some of the maturation defects of haemopoiesis.
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PMID:Expression of Epstein-Barr virus latent membrane protein influences self-renewal and differentiation in a multipotential murine haemopoietic 'stem cell' line. 838 64

We have previously demonstrated that avian osteoclasts contain high levels of 17 beta-estradiol (17 beta E2) receptors and respond to 17 beta E2 treatment with a dose-dependent decrease in in vitro resorption of [3H] proline-labeled bone particles. To more accurately assess the influence of 17 beta E2 on osteoclastic activity, the specificity of estrogen modulation of resorption levels was determined using a quantitative pit resorption assay. Treatment with 17 beta E2 significantly decreased the number of osteoclast resorption pits formed compared with that after either vehicle or 17 alpha E2 treatment. Cotreatment with 17 beta E2 and hydroxytamoxifen (a complete 17 beta E2 antagonist in birds) abrogated the influence of 17 beta E2 on resorption activity. To elucidate the mechanism by which 17 beta E2 inhibits osteoclast activity, the effects of 17 beta E2 on the steady state mRNA levels of two avian osteoclast lysosomal proteins, lysozyme and a lysosomal membrane protein (LEP-100), were examined. Using highly purified avian osteoclasts, 17 beta E2 was shown to decrease lysosomal protein mRNA levels in a dose-dependent manner within 8 h of treatment in a process that required de novo protein synthesis. This response was specific for 17 beta E2, since the inactive stereoisomer 17 alpha E2 had no effect. Furthermore, coincubation of 17 beta E2 with hydroxytamoxifen eliminated the 17 beta E2 influence. After removal of 10(-8) M 17 beta E2, lysosomal gene mRNA levels returned to near-normal levels within 24 h. This is consistent with the previously reported ability of avian osteoclast-mediated resorption activity to recover from 17 beta E2 treatment. Lysozyme protein levels similarly decreased after 17 beta E2 treatment. These data suggest that avian osteoclasts are target cells for 17 beta E2 in vitro, that osteoclast activity in vivo is likely to be modulated by circulating levels of 17 beta E2, and that the 17 beta E2 inhibition of osteoclast resorption activity may be mediated at least in part via regulation of osteoclast lysosomal gene expression.
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PMID:Estrogen modulation of avian osteoclast lysosomal gene expression. 844 Jan 93

The Serratia marcescens extracellular nuclease is a secreted protein that is subject to growth phase and SOS control. Regulatory mutants affecting nuclease expression have been isolated that define a new locus, nucC, essential for transcription of the nuclease gene nucA. The cloned nucC gene is able to activate efficient expression from the nucA promoter in Escherichia coli, where it normally is poorly expressed. NucC is very similar to the bacteriophage P2 Ogr protein, a transcriptional activator essential for P2 late gene expression. NucC is able to replace P2 Ogr to support the growth of P2 ogr- mutants in E. coli. Ogr is a poor activator of the nuclease promoter in E. coli, but the related delta gene product from satellite phage P4 is highly effective. The presence of genes encoding a lysozyme and a putative porin or holin in the nucC operon suggests that nucC may be part of a cryptic prophage genome. The putative holin-like membrane protein is required in E. coli for extracellular secretion of the S. marcescens nuclease.
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PMID:Regulation of the Serratia marcescens extracellular nuclease: positive control by a homolog of P2 Ogr encoded by a cryptic prophage. 859 95

The virulence plasmid pYVe of Yersinia enterocolitica codes for the production of the outer membrane protein YadA and the secretion of several proteins, called Yops, which may protect this bacterium against killing by human granulocytes. Granulocytes kill ingested microorganisms by oxygen-dependent and oxygen-independent mechanisms, the latter including antimicrobial polypeptides. The aim of this study was to determine whether virulent (pYVe+) Y. enterocolitica and plasmid-cured avirulent (pYVe-) Y. enterocolitica differ in susceptibility to antimicrobial polypeptides extracted from granules of human granulocytes. The acetic acid granule extract contained several polypeptides with antimicrobial activity against Y. enterocolitica as determined by gel overlay and radial diffusion assays. Two of these polypeptides were identified as lysozyme and defensins. pYVe+ Y. enterocolitica was less susceptible than pYVe- Y. enterocolitica to the antimicrobial activity of granule extract, lysozyme, and defensins as determined in a suspension assay, which indicated that the pYVe plasmid mediates a reduced susceptibility to these polypeptides. The role of YadA in the resistance to antimicrobial polypeptides was analyzed by using mutants of Y. enterocolitica that specifically lack or express YadA. The results demonstrated that YadA conferred resistance to the killing of Y. enterocolitica by the granule extract. Together, these results indicate that the plasmid-encoded factor YadA contributes to the resistance of Y. enterocolitica to the killing by antimicrobial polypeptides of human granulocytes.
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PMID:Role of YadA in resistance to killing of Yersinia enterocolitica by antimicrobial polypeptides of human granulocytes. 861 74


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