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)

Investigations on the photodynamic action of psoralens with DNA were performed, using experimental techniques of fluorescence lifetime and NMR-CIDNP, as well as SCF-MO and CNDO molecular orbital calculations. It has been shown that the formation of a biradical through the triplet state is the decisive step for psoralen dimer formation, as well as for cyclobutane addition with thymine, while singlet oxygen production is responsible for enzyme inactivation (e.g., lysozyme and trypsin). The molecular orbital calculations, in agreement with experimental results, indicate that the differences in biological effectivity of different psoralens are based on variations in triplet formation probability.
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PMID:Investigations on the mechanism of photodynamic action of different psoralens with DNA. 661 9

Evidence is presented from 1H NMR studies for non-random conformational behaviour in denatured lysozyme in aqueous solution. A method is presented which permits the assignment of resonances in the 1H NMR spectrum of the denatured protein by observing magnetisation transfer from resonances of the native state. The use of these experiments in characterising the denatured state and the significance of these studies for the investigation of protein folding are discussed.
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PMID:Proton NMR studies of denatured lysozyme. 672 56

1. The outer membrane of a phospholipase A-deficient mutant of Escherichia coli K12, isolated without the use of EDTA and lysozyme, showed the same freeze-fracture morphology as that seen in cells and remained stable for hours as observed by 31P-NMR. 2. 31P-NMR spectroscopy of the isolated outer membranes revealed that the lipopolysaccharide exists in the same physical state as in phospholipid-lipopolysaccharide liposomes and is most probably arranged in a bilayer at 37 degrees C. The outer membrane contains most or all of the phospholipids at 37 degrees C, and all the phospholipids at 20 degrees C, as a bilayer. 3. The 31P-NMR spectroscopy of the outer membranes from a mutant strain lacking the major outer membrane protein b, c and d (60% of the total outer membrane protein) yields virtually the same spectrum as the wild-type outer membranes, although most of the particles and pits which were observed in wild-type outer membranes in freeze-fracture electron microscopy were absent. 4. Whereas treatment of wild-type outer membranes with calcium ions has no effect on the 31P-NMR spectrum, treatment with EDTA results in more motion of the lipopolysaccharide.
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PMID:31P nuclear magnetic resonance and freeze-fracture electron microscopy studies on Escherichia coli. III. The outer membrane. 676 82

Deuterium NMR spectra are reported for lysozyme crystals, powders, and frozen solutions. At high water contents the spectrum is a superposition of a narrow central component and a quadrupole doublet. The quadrupole splitting and the relaxation rates of both components, monitored as a function of water content and temperature, are discussed in terms of models for the water-protein interaction. The anisotropy of the water molecule motion is clearly demonstrated by the deuterium quadrupole splitting observed in the protein single crystal, but such splittings were not found in protein powders and frozen protein solutions. We therefore suggest that the most useful view of such data is to consider the water-protein interactions at the surface to be mixed rapidly and that a distribution of interactions be invoked rather than an oversimplified view often taken of a two or n-site mixing where n is small.
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PMID:Deuterium NMR of water in immobilized protein systems. 680 51

1H-NMR relaxation times are reported for native and thermally denatured lysozyme aqueous solutions measured as the function of the proton mole fraction in the sample. A two-exponential character of proton longitudinal relaxation function was observed for native lysozyme solutions: the fast component was attributed to the non-exchangeable protein protons, the slow one to water protons. Purely exponential decay of longitudinal magnetization was observed for the thermally denatured samples. This has been explained in terms of a fast spin exchange model. The contributions of the protein protons to the water proton relaxation rate in native and thermally denatured samples were determined, too.
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PMID:1H-NMR relaxation studies of native and thermally denatured lysozyme solutions: an isotope dilution experiment. 688 40

Reductive methylation of hen egg-white (HEW) lysozyme with [13C]formaldehyde and NaCNBH3 and subsequent 13C NMR spectroscopy reveal resonances for each of the mono- and dimethyl derivatives of the six lysyl epsilon-amino groups and the NH2 terminus. Each resonance has a unique chemical shift, pKa, and chemical shift change upon deprotonation. The assignment of the resonances arising from the N alpha,N-dimethyl and N alpha-monomethyl NH2 terminus has been made as have resonance assignments for the two lysyl residues which crystallographic studies indicate are involved in ion pair interactions (Imoto, T., Johnson, L. N., North, A. C. T., Phillips, D. C., and Rupley, J. A. (1972) in The Enzymes (Boyer, P. D., ed) 3rd Ed, Vol. 7, pp. 665-868, Academic Press, New York). One resonance, tentatively assigned to the lysine 1 (epsilon NH3+) which forms an ion pair with glutamic acid 7 (gamma COO-), has a highly perturbed chemical shift which shows a biphasic titration curve (N epsilon, N-dimethyl pKa values 10.0 and 2.6). A similar titration curve is observed for a N epsilon-monomethyl lysyl residue. The resonance for lysine 13 (epsilon NH3+), which forms an ion pair with the carboxyl terminus, leucine 129 (alpha COO-), has been assigned by removal of leucine 129 with carboxypeptidase whereupon only one pair of mono- and dimethyl lysyl resonances is greatly perturbed. The pKa of N epsilon,N-dimethyl lysine 13 is 9.3 in des-Arg-Leu-lysozyme in contrast to 9.8 for the intact enzyme. Thus, it appears that both of the intramolecular ion pairs predicted by x-ray crystallography exist in the solution structure of HEW lysozyme.
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PMID:Intramolecular interactions of amino groups in 13C reductively methylated hen egg-white lysozyme. 706 54

The individual rates of solvent exchange of the six tryptophan indole NH hydrogens of lysozyme in 2H2O have been measured over a wide range of temperatures by using 1H NMR. Two distinct mechanisms for exchange have been identified, one characterized by a high activation energy and the other by a much lower activation energy. The high-energy process has been shown to be associated directly with the cooperative thermal unfolding of the protein and is the dominant mechanism for exchange of the most slowly exchanging hydrogen even 15 degrees C below the denaturation temperature. Rate constants and activation for the folding and unfolding reactions were obtained from the experimental exchange rates. At low temperatures, a lower activation energy mechanism is dominant for all hydrogens, and this can be associated with local fluctuations in the protein structure which allows access of solvent. The relative exchange rates and activation energies can only qualitatively be related to the different environments of the residues in the crystal structure. There is provisional evidence that a mechanism intermediate between these two extremes may be significant for some hydrogens under restricted conditions.
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PMID:Mechanisms of hydrogen exchange in proteins from nuclear magnetic resonance studies of individual tryptophan indole NH hydrogens in lysozyme. 707 52

Resonances of H alpha, H beta, and HN (amide) protons have been assigned in the NMR spectrum for ten residues in a region of beta-sheet structure of lysozyme. The assignments were achieved primarily by interpretation of nuclear Overhauser effects in conjunction with spin decoupling. The HN hydrogens involved in main-chain hydrogen bonding were found to exchange slowly with D2O solvent, although one of the most slowly exchanging HN hydrogens is not classified as being involved in a hydrogen bond in the crystal structure. Spin-spin coupling constants between H alpha protons and HN and H beta protons correlated well with values predicted from the crystal structure by means of the Karplus relationship. For no residues are the coupling constant discrepancies greater than 2.5 HZ. This indicates that for the residues studied here the torsion angles phi and chi 1 defined in the crystal structure describe accurately, generally well within 20 degrees, those for the average solution state.
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PMID:Studies of beta-sheet structure in lysozyme by proton nuclear magnetic resonance. Assignments and analysis of spin-spin coupling constants. 713 26

The forward rate constant for the binding of Bromophenol blue to lysozyme is estimated to be 10(5)M-1 X S-1 at room temperature and ionic strength 0.01, from the line broadening of the 1H-NMR spectrum of Bromophenol blue at 270 MHz. The broadening of the 1H-NMR line corresponding to histidine-15 of lysozyme, in the presence of Bromophenol blue in solution at pH 4.5, suggests that the binding site of Bromophenol blue is not far from this protein residue. The extent of this broadening is pH-dependent and can be interpreted in terms of the average coulombic interaction between the dye and His-15. Since Bromophenol blue is known to inhibit lytic activity of lysozyme towards cell wall substrates, we can say that the region near His-15 may also be important for the efficient catalytic activity of lysozyme.
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PMID:Binding site of the dye in Bromophenol blue-lysozyme complex. Proton magnetic resonance study in aqueous solutions. 715 Jun 3

The in vivo incorporation of deuterated amino acids into egg white proteins of Japanese quail is described. Using a synthetic diet, the level of incorporation of selectively deuterated tyrosine, tryptophan, histidine, and phenylalanine into lysozyme was greater than 80% as demonstrated by proton NMR. Load and load-chase experiments using [3H]phenylalanine or [3H]leucine monitored the fast uptake time (t 1/2 = 2 days) and confirmed the high levels of incorporation. The potential of this system for preparation of other proteins for NMR spectroscopy is discussed.
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PMID:Efficient incorporation of deuterated amino acids into quail egg white proteins for nuclear magnetic resonance studies. 746 10


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