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)

In the present study, peptidoglycan from Rickettsia prowazekii, an obligate intracellular bacterium, was purified. The rickettsial peptidoglycan is like that of gram-negative bacteria; that is, it is sodium dodecyl sulfate insoluble, lysozyme sensitive, and composed of glutamic acid, alanine, and diaminopimelic acid in a molar ratio of 1.0:2.3:1.0. The small amount of lysine found in the peptidoglycan preparation suggests that a peptidoglycan-linked lipoprotein(s) may be present in the rickettsiae. D-Cycloserine, a D-alanine analog which inhibits the biosynthesis of bacterial cell walls, prevented rickettsial growth in mouse L929 cells at a high concentration and altered the morphology of the rickettsiae at a low concentration. These effects were prevented by the addition of D-alanine. This suggests that R. prowazekii contains D-alanine in the peptidoglycan and has D-Ala-D-Ala ligase and alanine racemase activities.
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PMID:Analysis of the peptidoglycan of Rickettsia prowazekii. 830 May 46

Carbohydrates are T cell independent antigens because they do not bind to MHC molecules. However, glycopeptides might potentially bind to MHC molecules via their peptide component for presentation to T cells. We have conjugated the disaccharide galabiose [Gal alpha (1-4)Gal beta] to the amino terminus of a T cell peptide determinant from hen egg-white lysozyme [HEL(52-61)]. The resulting glycopeptide (Gal2-52-61) and a nonglycosylated analogue containing tyrosine and glutamic acid at the amino-terminus (YE-52-61) bound equally well to purified I-Ak. T cell hybridomas were produced after immunization with Gal2-52-61. Many of the T cell hybridomas were glycopeptide-specific and responded to Gal2-52-61 but not to nonglycosylated synthetic peptides or to HEL presented by APC, indicating that the carbohydrate moiety influenced T cell recognition. Recognition was lost with the amino terminal attachment of the disaccharide to a peptide six amino acids longer at the amino terminus than HEL(52-61). Recognition also was lost with peptides containing only a single galactosyl residue or with galabiose bound to a different I-Ak binding peptide. T cells directed to Gal2-52-61 recognized glycopeptides having significant variation in the disaccharide structure, such as HEL(52-61) glycopeptides carrying lactose, cellobiose, or hepta-o-acetylated galabiose. Peptide residues were important features of the T cell epitope; Ala substitutions of two critical T cell contact residues of HEL(52-61) (Tyr53 and Leu56) abrogated T cell reactivity to the glycopeptides without affecting binding to I-Ak. In conclusion, we propose that these T cells recognize a peptide conformation specific to glycopeptide-I-Ak complexes and that this recognition does not involve specific interaction between the carbohydrate moiety and the T cell receptor.
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PMID:Glycopeptides bind MHC molecules and elicit specific T cell responses. 836 Apr 71

A strategy for the structural characterization of the four major NaBH4-reduced peptidoglycan monomers derived from muramidase-digested peptidoglycan from the cyanelles of the flagellate Cyanophora paradoxa Korschikoff is described. Initial molecular weight determination of these glycopeptides was performed by positive and negative ion plasma desorption mass spectrometry. Due to the presence of two pairs of disaccharide tripeptide and disaccharide tetrapeptide monomers differing in mass by 112 units, respectively, an as yet unknown peptidoglycan modification either at the carbohydrate or at the peptide moiety was assumed. beta-Elimination of the disaccharide unit from the unreduced peptidoglycan monomers yielded the corresponding (modified) N1-lactyltripeptides and -tetrapeptides, respectively. These peptides, N-terminally blocked with lactic acid, unambiguously showed the modification to be located on the peptide moiety. By positive ion fast atom bombardment/hybrid tandem mass spectrometry of the reduced peptidoglycan monomers as well as of the corresponding deglycosylated monomers (= N1-lactylpeptides) the modification was determined to be linked to the glutamic acid moiety. Based on combined data from plasma desorption mass spectrometry, tandem mass spectrometry, accurate mass measurement and amino acid analysis of the acid hydrolysate after derivatization with o-phthaldialdehyde by high-performance liquid chromatography we could establish the structure of the modification as N-acetylputrescine. Finally, the confirmation of the linkage of the glutamic acid to diaminopimelic acid via the gamma-COOH was based on the presence of a-type peptide backbone fragment ions in the positive ion plasma desorption mass spectra of the modified N1-lactylpeptides.
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PMID:Structural characterization of the cyanelle peptidoglycan of Cyanophora paradoxa by 252Cf plasma desorption mass spectrometry and fast atom bombardment/tandem mass spectrometry. 839 1

In order to correlate between spectroscopic and structural changes in a protein, the environment of Trp 135 in T4 lysozyme was deliberately perturbed by the replacement of Gln 105 with alanine (Q105A), glycine (Q105G), and glutamic acid (Q105E). In wild-type lysozyme, Trp 135 is buried, but the indole nitrogen is hydrogen-bonded to the side-chain of Gln 105. In the Q105G and Q105A mutant structures, the indole nitrogen becomes accessible to solvent. Crystallographic analysis shows that the structures of all of the mutants are similar to wild-type. There are, however, distinct rearrangements of the local solvent structure in response to the new side-chains. There are also small but significant changes in the relative orientations of the two domains of the protein that appear to result from a series of small, concerted movements of side-chains adjacent to residue 105. Evaluation of the fluorescence and phosphorescence of the mutant proteins in terms of their observed three-dimensional structures shows that large spectral changes do not necessarily imply large changes in structure or in static solvent accessibility. Increases in polar relaxation about the excited state of tryptophan may be the result of only small increases in local dynamics or solvent exposure. 1H-NMR was also used to monitor the effects of the substitutions on Trp 138. In Q105E, but not in Q105G, Q105A and WT, the H epsilon chemical shift of Trp 138 is very pH-dependent, apparently reflecting the titration of Glu 105 which has a spectroscopically determined pKa of 6.0. The elevation of the pKa of Glu 105 in Q105E is also reflected in the pH dependence of the stability of this mutant.
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PMID:Perturbation of Trp 138 in T4 lysozyme by mutations at Gln 105 used to correlate changes in structure, stability, solvation, and spectroscopic properties. 846 Jan 10

The interaction of different species variants of cytochrome c and myoglobin, as well as hen egg white lysozyme, with the hard Lewis metal ions Al3+, Ca2+, Fe3+, and Yb3+ and the borderline metal ion Cu2+, immobilized to iminodiacetic acid (IDA)-Sepharose CL-4B, has been investigated over the range pH 5.5-8.0. With appropriately chosen buffer and metal ion conditions, these proteins can be bound to the immobilized Mn+-IDA adsorbents via negatively charged amino acid residues accessible on the protein surface. For example, tuna heart cytochrome c, which lacks surface-accessible histidine residues, readily bound to the Fe3+-IDA adsorbent, while the other proteins also showed affinity toward immobilized Fe3+-IDA adsorbents when buffers containing 30 mM of imidazole were used. These studies document that protein selectivity can be achieved with hard-metal-ion immobilized metal ion affinity chromatography (IMAC) systems through the interaction of surface-exposed aspartic and glutamic acid residues on the protein with the immobilized Mn+-IDA complex. These investigations have also documented that the so-called soft or borderline immobilized metal ions such as the Cu2+-IDA adsorbent can also interact with surface-accessible aspartic and glutamic acid residues in a protein-dependent manner. A relationship is evident between the number of clustering of the surface-accessible aspartic and glutamic residues and protein selectivity with these IMAC systems. The use of elution buffers which contain organic compound modifiers which replicate the carboxyl group moieties of these amino acids on the surface of proteins is also described.
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PMID:Protein selectivity in immobilized metal affinity chromatography based on the surface accessibility of aspartic and glutamic acid residues. 859 82

Structural and functional features of plant lysozymes are reviewed. All lysozymes also have chitinase activity, but not all plant chitinases are also lysozymes. However, for many chitinases it is not yet known if they also possess lysozyme activity. Enzymes with lysozyme activity occur in different, structurally unrelated, families of chitinases. Plant chitinases with lysozyme activity are basic enzymes with high isoionic points. Their lysozyme activities have a shart pH optimum around pH 4.5-5.0, while they show chitinase activities in a much broader pH range. High lysozyme activities are observed at low ionic strength values (0.05). The X-ray structure of a lysozyme/chitinase from latex of the rubber tree, Hevea brasiliensis, is presented. This enzyme is also known under the name hevamine. It belongs to the family 18 or h-type chitinases (also called class III chitinases). The structure consists of an alpha/beta barrel fold, which has not been found in other chitinase or lysozyme structures. A glutamic acid residue may be catalytically active in the substrate-binding cleft of the enzyme. Other plant lysozymes are homologous with the family 19 or b-type chitinases (class I, II and IV). The X-ray structure of barley chitinase, a representative of this family with negligible lysozyme activity, has a similar folding as found in animal and phage lysozymes.
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PMID:Plant lysozymes. 876 95

The three-dimensional structure of hevamine, a plant enzyme with chitinase and lysozyme activity, has been refined at 1.8 A resolution to an R-factor of 14.9% and a free R-factor of 19.6%. The final model consists of all 273 amino acid residues and 206 ordered water molecules. Two non-proline cis-peptides were identified, involving Phe32 and Trp255, both of which are implicated in substrate binding. Other glycosyl hydrolase family 18 proteins with known three-dimensional structure are bacterial chitinase A, endo-beta-N-acetylglucosaminidase F1, endo-beta-N-acetylglucosaminidase H, and the two plant proteins concanavalin B and narbonin, which have no known enzymatic activity. All these structures contain a (beta alpha)8 barrel fold, with the two family 18 consensus regions roughly corresponding to the third and fourth barrel strands. This confirms the grouping of these proteins into family 18, which was only based on weak and local sequence similarity. The substrate specificity of the enzymes is determined by the loops following the barrel strands that form the substrate binding site. All enzymes have an aspartic acid and a glutamic acid residue in positions identical with Asp 125 and the catalytic Glu127 of hevamine. The lack of chitinase activity of concanavalin B and narbonin can be explained by the absence of one of these carboxylate groups, and by differences in the loops that form the substrate-binding cleft in hevamine.
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PMID:The 1.8 A resolution structure of hevamine, a plant chitinase/lysozyme, and analysis of the conserved sequence and structure motifs of glycosyl hydrolase family 18. 883 91

In the present study, the extent of heterogeneity in the high responder T cell response to the predominant epitope region of hen egg white lysozyme (HEL46-61) was examined. Through analyses of T cell proliferation and precursor frequency, the C3H T cell response is shown not to be limited to peptides containing the previously defined minimal epitope of residues 52-61, but rather is quite heterogeneous, encompassing much of the 46-61 sequence. Further characterization using a panel of T cell hybridoma clones revealed T cell recognition of diverse minimal epitopes within this region. Interestingly, these T hybridomas could be grouped into three distinct categories based on the ability to respond to peptides with or without the native arginine residue at position 61 (61-required, 61-inhibitory, dual responders). Using analogue peptides containing single amino acid substitutions at position 61, further heterogeneity within these hybridoma groups was identified, suggesting the presence of an extremely diverse T cell repertoire for the epitope region. The charge and/or size of the C-terminal residue appears to be a critical factor for certain clones; replacement of the native arginine residue with aspartic acid or glutamic acid enabled a nonstimulatory ligand to specifically antagonize a T cell hybridoma response. Collectively, these results strongly suggest that the C-terminal residue of the predominant epitope in high responder mice plays a critical role in T cell diversity and activation.
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PMID:Role of a C-terminal residue of an immunodominant epitope in T cell activation and repertoire diversity. 897 83

Classical model system: Poly-L-glutamic acid (Poly-Glu) was investigated in a disordered coil state (at pH-7.0) and in helix state (at pH 2.0) by Rayleigh scattering of Moessbauer radiation technique. Consider that the coil state of poly-Glu models unfolded (random coil) state and alpha-helix state models the fluctuating secondary structure (during consequent folding of protein) comparative analysis of dynamical properties of poly-Glu in different states with dynamical properties of different proteins in native state (alpha-helical myoglobin and HSA, partially beta-sheet lysozyme) and in intermediate (molten globule) state (alpha-lactalbumin) was performed. This comparison bring some surprising results: native alpha-helical proteins behave itself close to random coil, native partially beta-sheet protein behaves close to fluctuating secondary structure (alpha-helix) and the dynamic behaviour of molten globule state (partially beta-sheet alpha-lactalbumin) is not different from those behaviour of lysozyme and much more rigid than native alpha-helical proteins. As a result one cannot exclude the possibility that folding process and dynamical properties at different steps of the folding are very different for alpha-helical and beta-sheet proteins.
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PMID:[Comparison of dynamic properties of various globular proteins and polyglutamic acid in alpha-helical and coil states. Rayleigh scattering of Mossbauer radiation data]. 918

An acidic 1,2-alpha-mannosidase from fungus, Aspergillus saitoi (now designated Aspergillus phoenicis), is highly specific for 1,2-alpha-mannosidic linkage in the high-mannose type oligosaccharide at pH 5.0. The predicted amino acid sequence of several peptide regions, including aspartic acid and glutamic acid, bears striking similarities to 1,2-alpha-mannosidases from fungi, yeast and mouse. Active site determination of the enzyme expressed in Saccharomyces cerevisiae cells was performed by site-directed mutagenesis. Substitutions of Asp-269 to Glu and of the Glu-residues, Glu-273, Glu-411, Glu-414 and Glu-474, to Asp altered the drastic decrease of specific activities with Man alpha 1-2Man-OMe and Man9-GlcNAc2-PA as substrates and shifted the optimal pH of the mutant enzymes. From the present results, Asp-269 is probably in the ionized COO- form, whereas one of four glutamic acid residues, probably Glu-411, is the un-ionized COOH form according to the analogy of a plausible mechanism for lysozyme catalysis. It is assumed that three glutamic acid residues, Glu-273, Glu-414, and Glu-474, are probably binding sites of substrate.
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PMID:Five crucial carboxyl residues of 1,2-alpha-mannosidase from Aspergillus saitoi (A. phoenicis), a food microorganism, are identified by site-directed mutagenesis. 932 67


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