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

---

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

A new double-labelling procedure for amino acid analysis which requires only routine chromatographic equipment is described. When 1-fluoro-2,4-dinitro[3H]benzene is reacted with a mixture of 14C-labelled amino acids followed by reaction with the same 14C-labelled amino acid mixture diluted with an unlabelled sample of amino acids, the 3H:14C ratio in the resulting 2,4-dinitrophenyl (DNP) amino acid derivatives of the diluted sample will be increased in proportion to the quantity of unlabelled amino acid in the diluted sample. This procedure gave reliable results when applied to the known proteins insulin and lysozyme. The procedure is most advantageous when applied to amino acids which are unstable during acid hydrolysis or present in low molar fractions. When applied to the analysis of the bacteriorhodopsin in Halobacterium cutirubrum, this procedure showed the presence of one histidine residue and four tryptophan residues per mole protein but no cystine or cysteine; in general, the analyses obtained were consistent with those originally reported by Oesterhelt, D. and Stoeckenius, W. (1971) (Nature (London) New Biol. 233, 149-152) for bacteriorhodopsin of H. halobium.
...
PMID:A new double-labelling procedure for determination of amino acid composition: application to bacteriorhodopsin. 66 97

The hydrophobic cores of proteins are generally well packed, with few cavities. Mutations in which a bulky buried residue such as leucine or phenylalanine is replaced with a small residue such as alanine can create cavities in the core of a protein (our unpublished results). The sizes and shapes of such cavities can vary substantially depending on factors such as local geometry, whether or not a cavity already exists at the site of substitution, and the degree to which the protein structure relaxes to occupy the space vacated by the substituted residue. We show by crystallographic and thermodynamic analysis that the cavity created by the replacement Leu 99----Ala in T4 lysozyme is large enough to bind benzene and that ligand binding increases the melting temperature of the protein by 6.0 degrees C at pH 3.0. Benzene does not, however, bind to the cavity created by the Phe 153----Ala replacement. The results show that cavities can be engineered in proteins and suggest that such cavities might be tailored to bind specific ligands. The binding of benzene at an internal site 7 A from the molecular surface also illustrates the dynamic nature of proteins, even in crystals.
...
PMID:A cavity-containing mutant of T4 lysozyme is stabilized by buried benzene. 173 Dec 52

A reference method for the deconvolution of polarized fluorescence decay data is described. Fluorescence lifetime determinations for p-terphenyl, p-bis[2-(5-phenyloxazolyl)]benzene and N-acetyltryptophanamide (AcTrpNH2) show that with this method more reliable fits of the decays can be made than with the scatterer method, which is most frequently used. Analysis of the AcTrpNH2 decay with p-terphenyl as the reference compound yields an excellent fit with lifetimes of 2.985 ns for AcTrpNH2 and 1.099 ns for p-terphenyl (20 degrees C), whereas the AcTrpNH2 decay cannot be satisfactorily fitted when the scatterer method is used. The frequency of the detected photons is varied to determine the conditions where pulse pile-up starts to affect the measured decays. At detection frequencies of 5 kHz and 15 kHz, which corresponds to 1.7% and 5% respectively of the rate of the excitation photons no effects are found. Decays measured at 30 kHz (10%) are distorted, indicating that pile-up effects play a role at this frequency. The fluorescence and fluorescence anisotropy decays of the tryptophan residues in the proteins human serum albumin, horse liver alcohol dehydrogenase and lysozyme have been reanalysed with the reference method. The single tryptophan residue of the albumin is shown to be characterized by a triple-exponential fluorescence decay. The anisotropy decay of albumin was found to be mono-exponential with a rotational correlation time of 26 ns (20 degrees C). The alcohol dehydrogenase has two different tryptophan residues to which single lifetimes are assigned. It is found that the rotational correlation time for the dehydrogenase changes with excitation wavelength (33 ns for lambda ex = 295 nm and 36 ns for lambda ex = 300 nm at 20 degrees C), indicating a nonspherical protein molecule. Lysozyme has six tryptophan residues, which give rise to a triple-exponential fluorescence decay. A single-exponential decay with a rotational correlation time of 3.8 ns is found for the anisotropy. This correlation time is significantly shorter than that arising from the overall rotation and probably originates from intramolecular, segmental motion.
...
PMID:Application of a reference convolution method to tryptophan fluorescence in proteins. A refined description of rotational dynamics. 356 97

A radiochemical method for the determination of the amino terminus on very small amounts (0.5-5 nmol) of protein is described. The high sensitivity of the method is achieved by using undiluted 1-fluoro-2,4-dinitro-[3,5-3H]benzene [( 3H]Dnp-F) as the labelling reagent under conditions in which a maximum amount of radioactive label is incorporated. Chemical homogeneity is achieved by reacting with excess unlabelled Dnp-F. High recovery is obtained by adding Dnp-albumin as carrier protein. A mixture of Dnp 14C-labelled amino acids is added prior to hydrolysis and identification of the amino terminus is made on the basis of the 3H/14C ratios of the separated Dnp-amino acids. The method was tested on insulin, pancreatic ribonuclease, and lysozyme which gave high 3H/14C ratios only in the expected amino-terminal amino acids. Application to multiple forms of poly(C)-avid ribonuclease gave only amino-terminal lysine. Two of four putative isozymes of 17 beta-hydroxysteroid dehydrogenase had serine as the amino terminus while the other two had aspartic acid or asparagine.
...
PMID:A highly sensitive method for identification of amino termini of proteins: application to multiple forms of poly(C)-avid ribonuclease and 17 beta-hydroxysteroid dehydrogenase. 630 40

Colchicine fluoresces when bound to tubulin but not in water, dioxane, or benzene. The basis of the fluorescence has now been investigated. Colchicine fluoresces in higher alcohols and shows a blue shift as a function of chain length. Glycerol produces a higher fluorescence efficiency and a further blue shift. Plots of 1/fluorescence versus T/eta yield straight lines for both alcohols and glycerol/water mixtures. Fluorescence in glycerol/dimethyl sulfoxide mixtures, in which the dielectric constant remains unchanged, varies as a function of solvent viscosity. Even highly nonpolar solvents such as dioxane require a threshold viscosity for fluorescence to occur. When solvent polarity was decreased at constant viscosity, there was also an enhancement of colchicine fluorescence, but this effect appeared to be smaller than that obtained with increasing viscosity. Immobilization by covalent attachment of desacetylcolchicine to thyroglobulin, serum albumin, or lysozyme also promotes fluorescence from the drug. By contrast, the highly rigid analogue of colchicine, imerubine, fluoresces in water and is unaffected by viscosity changes. We concluded that a major contribution to colchicine fluorescence stems from immobilization of colchicine in the site and that this response to immobilization depends, in part, on the partially flexible nature of the drug. Since certain other flexible molecules such as auramine O, reduced flavines, and diarylalkanes also require increased viscosity or binding to macromolecules to fluoresce at room temperature, we propose that immobilization-enhanced fluorescence may be more common than heretofore believed.
...
PMID:Immobilization-dependent fluorescence of colchicine. 648 May 86

We report here a comprehensive infrared spectroscopic study of the interactions between the anesthetic nitrous oxide (N2O) and six proteins: lysozyme, cytochrome c, myoglobin, hemoglobin, serum albumin, and cytochrome c oxidase. Sites occupied by N2O molecules within these proteins were characterized. Three types of hydrophobic sites were found within the proteins. One with nu 3 near 2225 cm-1 is likely to be near peptide bond carbonyls; one with nu 3 near 2219 cm-1 may be near a benzene-like structure such as the side chains of phenylalanine and tyrosine; and the other with nu 3 near 2215 cm-1 is likely to be in a nonpolar alkane-like environment provided by the side chains of Leu, Ile, and Val residues. The amount of N2O molecules bound to myoglobin increases as the pH decreases from 9.2 to 5.2. N2O-protein interactions produced no detectable changes in the ligand-binding pockets of myoglobin, hemoglobin, and cytochrome c oxidase. N2O-induced secondary structure changes were detected only in the fully reduced cytochrome c oxidase, not in the fully oxidized oxidase and the other five proteins. N2O-induced conformational changes in the alpha beta-interface of hemoglobin and the h2 and h3 alpha-helices of human serum albumin were detected by monitoring the S-H stretch vibrations of cysteine residues. These findings provide direct evidence that anesthetic N2O interacts with proteins and occupies sites in the interior of the proteins.
...
PMID:Characterization of sites occupied by the anesthetic nitrous oxide within proteins by infrared spectroscopy. 792 38

The study was carried out in 156 men, including 49 nonsmokers and 47 smokers who had never been exposed to chemicals, 19 nonsmokers exposed to organic solvents, and 41 smokers exposed to organic solvents. The results of toxicological analysis of air in the working place carried out in the range depending on the type of solvents used in the process of lacquering of steel cans and on the data obtained from the producer showed that the solvents contained benzene, toluene, xylene and their derivatives partly hydrogenated, paraffin hydrocarbons, oleins, naphthenes (components of painter's naphtha), monohydric and polyhydric alcohols (butanol, cyclohexanol, butyloglycol), esters (ethylglycol acetate, butyl acetate) and ketones (methyl isobutyl ketone, cyclohexanone). Measured benzene concentrations varied from 0 to 370 mg x m-3 (0 to 116 ppm), with arithmetic mean annual averages of about 100 mg x m-3 (31 ppm) in the late 1960's and less than 50 mg x m-3 (16 ppm) in the 1970's. In the 1980's values for the TWA were 0-38 mg x m-3 (0-12 ppm) with arithmetic mean averages of about 19 mg x m-3 (6 ppm) and for the level of benzene 0-351 mg x m-3 (0-110 ppm), with arithmetic mean annual averages of about 48 mg x m-3 (15 ppm). Phenol concentration in the urine of the workers in groups was 7.9 +/- 3.5; 10.0 +/- 5.8; 16.8 +/- 6.2 and 18.4 +/- 9.7 mg x 1(-1) respectively. Hippuric acid concentration in the urine of the workers in groups was 496 +/- 326, 538 +/- 341, 982 +/- 420 and 1107 +/- 507 mg x 1(-1) respectively. The parameters of immunity and proteins acute phase reaction were determined, measuring the count of T, B, and "non-T, non-B" circulating lymphocytes, the concentration of immunoglobulins, lysozyme, C3c, C4, alpha 1-acid glycoprotein, haptoglobulin and ceruloplasmin in serum. The results of the presented study suggest the role of cigarette smoking as a co-factor in the immunological changes brought out by occupational exposure to organic solvents. This phenomenon is reflected in the changes of IgA, IgD, IgG, IgM and lysozyme in the serum, and number of circulating T cells.
...
PMID:The effect of cigarette smoking on the indexes of immunity and acute phase reaction in subjects with occupational exposure to organic solvents. 830 89

Water sorption isotherms at 27 degrees C have been measured for lysozyme and chymotrypsin in suspensions of toluene, di(n-butyl) ether, n-propanol, and a solution of 1M n-propanol in benzene. Sorption isotherms for the different suspensions are compared by converting solvent water content to the thermodynamic activity of water in each solvent. The sorption behavior is also compared to that for the two proteins hydrated from the vapor phase. At low water activities, all sorption isotherms are similar when compared on the basis of water activity. However, at higher activities, water sorption by the proteins in the organic suspensions is suppressed relative to the sorption of water vapor. The greatest suppression is observed for n-propanol, which suggests that the suppression may be due to a competition for water-binding sites on the protein by the organic solvent. Sorption isotherms at low water activities have also been predicted using a thermodynamic model in which it is assumed that water binds selectively to the ionizable residues on the surface of the protein. A comparison of predicted and measured sorption isotherms shows that the model can provide reasonable estimates of water sorption in nonpolar or moderately polar organic solvent suspensions at low levels of hydration.
...
PMID:The hydration of proteins in nearly anhydrous organic solvent suspensions. 836 56

We have investigated the magnitude and timescale of fluctuations within the core of a protein using the exchange kinetics of indole and benzene binding to engineered hydrophobic cavities in T4 lysozyme. The crystal structures of variant-benzene complexes suggest that relatively large scale fluctuations (1-2 angstrom) of backbone atoms are required for entry of these ligands into the core. Nonetheless, these ligands enter the cavities rapidly, with bimolecular rate constants of approximately 10(6)-10(7) M(-1) s(-1) and a low activation barrier, 2-5 kcal mol(-1). These results suggest that protein cores undergo substantial fluctuations on the millisecond to microsecond timescale and that entry of small molecules into protein interiors is not strongly limited by steric occlusion.
...
PMID:Access of ligands to cavities within the core of a protein is rapid. 864 37

Several variants of T4 lysozyme have been identified that sequester small organic ligands in cavities or clefts. To evaluate potential binding sites for non-polar molecules, we screened a number of hydrophobic large-to-small mutants for stabilization in the presence of benzene. In addition to Leu99-->Ala, binding was indicated for at least five other mutants. Variants Met102-->Ala and Leu133-->Gly, and a crevice mutant, Phe104-->Ala, were further characterized using X-ray crystallography and thermal denaturation. As predicted from the shape of the cavity in the benzene complex, mutant Leu133-->Gly also bound p-xylene. We attempted to enlarge the cavity of the Met102-->Ala mutant into a deep crevice through an additional substitution, but the double mutant failed to bind ligands because an adjacent helix rearranged into a non-helical structure, apparently due to the loss of packing interactions. In general, the protein structure contracted slightly to reduce the volume of the void created by truncating substitutions and expanded upon binding the non-polar ligand, with shifts similar to those resulting from the mutations.A polar molecule binding site was also created by truncating Arg95 to alanine. This creates a highly complementary buried polar environment that can be utilized as a specific "receptor" for a guanidinium ion. Our results suggest that creating a deficiency through truncating mutations of buried residues generates "binding potential" for ligands with characteristics similar to the deleted side-chain. Analysis of complex and apo crystal structures of binding and non-binding mutants suggests that ligand size and shape as well as protein flexibility and complementarity are all determinants of binding. Binding at non-polar sites is governed by hydrophobicity and steric interactions and is relatively permissive. Binding at a polar site is more restrictive and requires extensive complementarity between the ligand and the site.
...
PMID:Generation of ligand binding sites in T4 lysozyme by deficiency-creating substitutions. 951 55


1 2 3 4 5 6 Next >>

---