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)

Structural studies were carried out on the polymer chains and their linkage regions in two kinds of teichoic acids, poly(N-acetylglucosamine 1-phosphate) [poly(GlcNAc-1-P)] and glycerol teichoic acid, bound to peptidoglycan in the cell walls of Bacillus pumilus AHU 1650. The poly(GlcNAc-1-P)-glycan complex isolated from lysozyme digests of the cell walls contained mannosamine and glycerol as minor components. On the basis of proton NMR spectroscopic data and isolation of N-acetylglucosamine 4-phosphate from acid hydrolysates, the poly(GlcNAc-1-P) was shown to be a polymer in which N-acetylglucosamine 1-phosphate units are joined at C-4 of the glucosamine residues. Mild alkaline hydrolysis of the poly(GlcNAc-1-P)-glycan complex gave a mannosamine-linked glycan fragment and the acidic polymer fraction that contained glycerol residues. Mild acid treatment of the mannosamine-linked glycan fragment gave the linkage disaccharide, ManNAc(beta 1----4)GlcNAc, whereas the acidic polymer fraction was degraded by this treatment into N-acetylglucosamine 4-phosphate and a glycerol-containing fragment characterized as P-(Gro-P)7 (Gro = glycerol). On the other hand, direct mild acid hydrolysis of the complex gave a fragment characterized as P-(Gro-P)7-ManNAc(beta 1----4)GlcNAc. These results lead to a conclusion that in the cell walls the poly(GlcNAc-1-P) chain is attached to peptidoglycan through a linkage unit, (Gro-P)7-ManNAc(beta 1----4)GlcNAc. By means of similar procedures, it was shown that the other cell wall polymer, glycerol teichoic acid, is also attached to peptidoglycan through the same disaccharide, ManNAc(beta 1----4)GlcNAc.
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PMID:Structural studies on the linkage unit between poly(N-acetylglucosamine 1-phosphate) and peptidoglycan in cell walls of Bacillus pumilus AHU 1650. 399 10

Double-quantum filtered COSY and triple-quantum filtered COSY techniques have been compared for the tripeptide Gly-Tyr-Gly and for human lysozyme. The insertion of a triple-quantum filter in the COSY experiment leads to dramatic spectral simplification in the fingerprint region of the spectrum and permits the specific identification of glycine spin systems in the complex 1H NMR spectra of proteins. The assignment of these peaks to glycine H alpha can be confirmed using 2D double-quantum correlated spectroscopy.
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PMID:Identification of glycine spin systems in 1H NMR spectra of proteins using multiple quantum coherences. 400 58

The structure of polysaccharide prepared by lysozyme digestion from the cell wall of Propionibacterium acnes strain C7 was examined. The polysaccharide fraction was composed of glucose, galactose, mannose, galactosamine, and diaminomannuronic acid in a molar ratio of 1:1:0.3:1:2. By Smith degradation of the polysaccharide, diaminouronic acid-containing fractions were obtained, and the configuration of diaminouronic acid was identified as 2,3-diacetamido-2,3-dideoxymannuronic acid [Man(NAc)2A] by means of 1H-NMR and 13C-NMR spectroscopic analyses. The results of analyses involving methylation and partial acid hydrolysis led to the conclusion that the polysaccharide has the repeating unit----6)Gal(alpha 1----4)Man(NAc)2A(beta 1----6)Glc(alpha 1----4)Man(NAc)2A (beta 1----3)GalNAc(beta 1--. In addition, a portion of the galactose residues were substituted at C-4 by alpha 1----2 linked mannotriose.
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PMID:Structure of acidic polysaccharide from cell wall of Propionibacterium acnes strain C7. 403 Jul 44

The effects of motional averaging on the analysis of vicinal spin-spin coupling constants derived from proton NMR studies of proteins have been examined. Trajectories obtained from molecular dynamics simulations of bovine pancreatic trypsin inhibitor and of hen egg white lysozyme were used in conjunction with an expression for the dependence of the coupling constant on the intervening dihedral angle to calculate the time-dependent behavior of the coupling constants. Despite large fluctuations, the time-average values of the coupling constants are not far from those computed for the average structure in the cases where fluctuations occur about a single potential well. The calculated differences show a high correlation with the variation in the magnitude of the fluctuations of individual dihedral angles. For the cases where fluctuations involve multiple sites, large differences are found between the time-average values and the average structure values for the coupling constants. Comparison of the simulation results with the experimental trends suggests that side chains with more than one position are more common in proteins than is inferred from X-ray results. It is concluded that for the main chain, motional effects do not introduce significant errors where vicinal coupling constants are used in structure determinations; however, for side chains, the motional average can alter deductions about the structure. Accurately measured coupling constants are shown to provide information concerning the magnitude of dihedral angle fluctuations.
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PMID:Vicinal coupling constants and protein dynamics. 405 69

Assignments in the 1H NMR spectrum for more than 120 resonances arising from 38 of the 130 amino acid residues of human lysozyme are presented. Assignments have been achieved using a combination of one and two-dimensional NMR techniques. Two-dimensional double-quantum correlated spectroscopy and relayed coherence transfer spectroscopy were found to be particularly useful for the identification of spin systems in the aromatic and methyl regions of the spectrum. These spin systems were assigned to specific residues in human lysozyme with reference to the X-ray crystal structure using one-dimensional nuclear Overhauser enhancement (NOE) data and a computer-based search procedure. Unique assignments were found for resonances of 27 amino acid residues even when a distance constraint on NOE effects of 0.7 nm was used in the search procedure; for the remaining residues closer constraints or additional information were required. The assignments include all but one of the resonances in the aromatic region of the spectrum and all the methyl group resonances in the region upfield of 0.6 ppm. The assignments presented here provide a basis for a comparison of the NMR spectra of human lysozyme and the more widely studied hen lysozyme.
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PMID:Assignment of resonances in the 1H NMR spectrum of human lysozyme. 407 83

The single His-15 of hen egg lysozyme reacts with 2,2,6,6-tetramethyl-4-(bromoacetamido)piperidinyl-1-oxy or 2,2,5,5-tetramethyl-3-(bromoacetamido)pyrrolidinyl-1-oxy to give a spin-labeled enzyme [Wien, R. W., Morrisett, J. D., & McConnell, H. M. (1972) Biochemistry 11, 3707-3716]. High-field 1H NMR spectra (300 and 500 MHz) of these species in 2H2O contain protein peaks selectively broadened by dipolar coupling to the unpaired electron spin. While usually difficult to discern in the spectrum itself, broadened resonances are revealed in difference spectra obtained by subtracting the original spectrum from one taken after reduction of the nitroxide radical with ascorbate. The heights of difference spectra peaks are related in a simple way to r-6, where r is the label to proton distance. These distances were used to solve for the location of the electron spin by using algorithms from distance geometry. The spin was found to lie in a hydrophobic groove between Phe-3 and Asp-87. These results demonstrate the feasibility of spin-labeling for accurate distance measurements in proteins through the use of distance geometry.
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PMID:Distance measurements in spin-labeled lysozyme. 609 43

Resonances of over 20 of the most slowly exchanging amide hydrogens have been identified and assigned in the 1H NMR spectrum of hen lysozyme. This was achieved by combining information about spin-spin coupling patterns with nuclear Overhauser enhancement measurements. A computer-based search program was used to permit the assumptions and constraints in this procedure to be closely defined and to reveal possible ambiguities. In addition, experimental values of coupling constants were compared with values calculated on the basis of the torsion angles found in the crystal structure. The close correlation between these gave further confidence in the assignment procedures and provided information concerning the nature of fluctuations about the average solution structure. The very slowly exchanging amide hydrogens are largely buried in alpha-helical and beta-sheet regions of the protein structure.
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PMID:Identification using 1H NMR spectroscopy of slowly exchanging amide hydrogens of hen lysozyme in solution. 609 89

Previous 77Se NMR relaxation time studies established the utility of 77Se NMR spectroscopy in studying low molecular weight (less than 500) selenium-containing molecules. Since the spin rotation and chemical shift anisotrophy mechanisms contributed significantly to the 77Se spin-lattice relaxation in these compounds, it was questionable as to whether the latter mechanism would be efficient enough to enable 77Se resonances to be observed in a reasonable period in high molecular weight selenobiomolecules. Thus, to address this problem, disulfide bonds of ribonuclease-A and lysozyme were reductively cleaved under denaturing conditions, and the resulting 7-8 sulfhydryl groups were treated with a new sulfhydryl group reagent containing selenium, 6,6'-diselenobis(3-nitrobenzoic acid), to give proteins containing covalently attached selenium in the form of selenenyl sulfides. The observation of high resolution 77Se NMR spectra of these proteins under denaturing conditions was accomplished. Five to six 77Se NMR resonances, which fell in a chemical shift range of 14-15 ppm, were observed for each protein and are compared to the chemical shifts of several model selenenyl sulfides derived from cysteine.
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PMID:Demonstration of the feasibility of observing nuclear magnetic resonance signals of 77Se covalently attached to proteins. 627 74

Techniques are now available for making extensive assignments in NMR spectra of proteins of moderate size (molecular weight 20,000 or less). Such assignments provide the first step for experiments designed to extract the full complement of NMR parameters for each group in a protein. The stage is set for exciting research scenarios in protein chemistry involving, for example, the determination of hydrogen exchange kinetics at all exchangeable positions whose half times are on the order of 100 ms (277) or longer than a few minutes (316, 569, 570); the characterization of intermediates in protein folding pathways (318); measurement of the distribution of internal motions within a protein molecule (573); a detailed description of the biophysical consequences of single amino acid replacements in small proteins (387); elucidation of the mechanisms of conformational transitions in proteins; and multiparametric characterization of the parts of an enzyme that participate in catalytic mechanisms. Small proteins for which extensive 1H NMR assignments have been made include lysozyme, several cytochromes, ferredoxins, myelin basic proteins, PTI and related proteinase inhibitors, proteinase inhibitors from seminal plasma and avian eggs, apamin, and several snake venom neurotoxins. (References are given in Table 1).
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PMID:Detailed analysis of protein structure and function by NMR spectroscopy: survey of resonance assignments. 633 Dec 88

Main points given in the above reports can be summarized as follows. Multiple unfolded forms exist for lysozyme as well as for RNase. The existence of fast- and slow-folding forms appears to be a general phenomenon; it has been confirmed for a number of globular proteins, which contain proline residues. The major slow refolding reaction of RNase A is a sequential process via structural intermediates. A rapidly formed intermediate has also been detected on the direct UF----N refolding pathway of lysozyme. The activated state for folding of lysozyme shows a conformation similar to the native protein in terms of packing of hydrophobic groups. This suggests that, in terms of compactness, the rate-limiting step occurs at a late stage of the refolding process. A protein homologous to lysozyme, alpha-lactalbumin, shows similar kinetics although alpha-lactalbumin shows an apparent equilibrium unfolding intermediate. The location of the rate-limiting step close to the native state has also been suggested for other proteins. It still remains open whether this is a general property of protein folding reactions. As shown for the unfolding of Mb, the multi-probe kinetic measurements will be a powerful tool for investigating the mechanism of folding, in particular for characterizing structural kinetic intermediates. The dynamics of local fluctuations of a well-defined part of RNase S can be monitored by NMR measurements of NH proton exchange. An increasing number of experimental and theoretical studies are focussing on the problem of protein dynamics. Application of NMR methods to protein folding should give extensive information about the structure of intermediates, which cannot be given by other techniques.
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PMID:Experimental studies of folding kinetics and structural dynamics of small proteins. 639 21


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