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)

Steady-state and transient fluorescence properties of turkey lysozyme, human lysozyme, and bovine alpha-lactalbumin are compared to those of hen lysozyme and hen lysozyme derivatives. Tryptophan fluorescence appears to be sufficiently sensitive to environment so that a small divergence in sequence can alter the fluorescence properties of one or more of the sequentially equivalent tryptophans in these proteins. Thus, an understanding of the fluorescence of one protein cannot necessarily be extended to a homologous protein in a simple manner, and the use of fluorescence to document structural similarity in homologous proteins is likely to be difficult. In addition, the results with alpha-lactalbumin and human lysozyme suggest that multiple conformations of these proteins exist in solution, and that interconversion of these conformations is slow compared to the fluorescence lifetime.
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PMID:Tryptophan fluorescence and homology in lysozymes and alpha-lactalbumins. 126 10

Advances in Raman optical activity (ROA) instrumentation, based on the employment of a backscattering geometry together with a back-thinned CCD detector and a single-grating spectrograph with a holographic edge filter, have now enhanced the sensitivity to the level necessary to provide vibrational ROA spectra of proteins in aqueous solution. Early results show at least four separate regions in protein ROA spectra associated with vibrations of the backbone which appear to characterize the alpha-helix, beta-sheet, reverse turn and random-coil secondary conformation content. Side-group ROA features also appear, with tryptophan particularly prominent in lysozyme and alpha-lactalbumin. ROA should become a sensitive new probe of protein folding and ligand-induced conformational change in aqueous solution.
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PMID:Vibrational Raman optical activity of enzymes. 129 Sep 37

Effects of calcium removal on the cell-clearing activity of alpha-lactalbumin (alpha-LA) and concomitant changes in conformational structure have been investigated as part of a continuing study of the activity found earlier [McKenzie, H.A. & White, F.H., Jr. (1987) Biochem. Int. 14, 347]. This activity is similar to that of lysozyme, whereby lysis of the bacterial cell wall is catalyzed. However, the specific activity of alpha-LA is on the order of 10(-6) that of lysozyme. Under conditions where activities of apo and native alpha-LA were approximately linear functions of the protein concentration, the maximal ratio of apo to native activity was 5.7:1, determined by comparison of second order velocity constants. The CD spectrum of apo alpha-LA is intermediate between that of the A state and the native protein. By NMR, the conformation of apo alpha-LA is similar to, but distinctly different from, that of the native protein. The apo form did not revert completely to the native state when Ca(II) was resupplied, consistent with a role for this cation in folding. It is suggested that the activity increase may result from a diminished constriction of the "cleft" region in alpha-LA.
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PMID:Studies on cell-clearing activity in alpha-lactalbumin. Effects of calcium removal on activity and conformation. 139 66

The three aspartic acid residues that form part of the Ca-binding site of mares' milk lysozyme have apparent pK values of 4.9, 4.3 and 4.1. The fluorescence of tryptophan has been used to compare the denaturation of mares' milk lysozyme by guanidinium chloride at various concentrations of Ca with that of hens' egg-white lysozyme (EC 3.2.1.17) and alpha-lactalbumin. Fluorescence revealed an intermediate stage in the denaturation of mares' milk lysozyme. The Ca-free form of mares' milk lysozyme is slightly more stable than that of alpha-lactalbumin, but its interaction with Ca is similar to that of alpha-lactalbumin, since only the native state binds Ca. Three-state models of denaturation can usefully be displayed on a ternary diagram.
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PMID:Effect of calcium on the stability of mares' milk lysozyme. 140 55

Breast secretions can be classified into two types according to their major protein components. Type I fluids contain Zn-alpha 2-glycoprotein, apolipoprotein D, and gross cystic disease fluid protein-15, while Type II fluids are characterized by the presence of lactoferrin, lysozyme, and alpha-lactalbumin. In this study, the polypeptide composition of breast secretions from 719 nonlactating women was evaluated by using polyacrylamide gel electrophoresis. The required amount for the analysis (1 microliter) was obtained from 50% of control women and from 75% of women with mammary disease. There were more secretors in premenopausal than in postmenopausal women, as well as in parous than in nulliparous women. Evaluation of factors affecting protein composition of breast secretions revealed that Type II fluids were found in the majority of women who had given birth in the last four years and in a high proportion of oral contraceptive users. After excluding both of these groups, Type II fluids were detected in 47% of patients with breast cancer, but only in 8% of control women and in 16% of women with benign breast diseases. Taken together, these results suggest that protein analysis of breast secretions could be an useful tool for the study of breast pathologies.
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PMID:Factors affecting protein composition of breast secretions from nonlactating women. 146 65

A methodology designed to address the inverse globular protein-folding problem (the identification of which sequences are compatible with a given three-dimensional structure) is described. By using a library of protein finger-prints, defined by the side chain interaction pattern, it is possible to match each structure to its own sequence in an exhaustive data base search. It is shown that this is a permissive requirement for the validation of the methodology. To pass the more rigorous test of identifying proteins that are not close sequence homologs, but that have similar structure, the method has been extended to include insertions and deletions in the sequence, which is compared to the fingerprint. This allows for the identification of sequences having little or no sequence homology to the fingerprint. Examples include plastocyanin/azurin/pseudoazurin, the globin family, different families of proteases and cytochromes, including cytochromes c' and b-562, actinidin/papain, and lysozyme/alpha-lactalbumin. Turning to supersecondary structure prediction, we find that alpha/beta/alpha fragments possess sufficient specificity to identify their own and related sequences. By threading a beta-hairpin through a sequence, it is possible to predict the location of such hairpins and turns with remarkable fidelity. Thus, the method greatly extends existing techniques for the prediction of both global structural homology and local supersecondary structure.
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PMID:Sequence-structure matching in globular proteins: application to supersecondary and tertiary structure determination. 146 45

From fluorescence measurements on mixtures of bis-ANS and equine lysozyme and from Ca(2+)-dependent hydrophobic interaction chromatography of equine lysozyme, it is demonstrated that Ca2+ binding induces a conformational change upon which hydrophobic regions in the protein become less accessible. Bis-ANS fluorescence titrations in the absence of Ca2+ and in 2 mM Ca2+ are also performed with equine alpha-lactalbumin variants B and C. These variants differ by an amino-acid exchange Asp----Ile at residue 95. The fluorescence titration curves indicate that the accessibility of the probe to the Ca2+ conformers is clearly influenced by the mutation. The Ca(2+)-dependent exclusion of a hydrophobic domain is used in a new and simplified method for preparing lysozyme and alpha-lactalbumins simultaneously from equine milk whey.
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PMID:Hydrophobic interaction of lysozyme and alpha-lactalbumin from equine milk whey. 150 92

The crystal structure of a calcium binding equine lysozyme has been determined at 2.5 A resolution by means of molecular replacement. The energy minimized equine lysozyme as the starting model, was refined with the molecular dynamics program, X-PLOR, and the R factor of the current model was found to be 24% without any water molecules. The conformation of the calcium binding loop is similar to that of alpha-lactalbumin. The profiles of backbone atomic displacements throughout the lysozyme and alpha-lactalbumin superfamilies are comparable as well as their homologous tertiary structures.
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PMID:Crystallographic studies of a calcium binding lysozyme from equine milk at 2.5 A resolution. 156 37

Calcium binding lysozyme from pigeon egg-white was crystallized by the hanging drop vapor diffusion technique using ammonium sulphate as a precipitant. The crystals belong to the orthorhombic system, space group P2(1)2(1)2(1), and have unit cell dimensions of a = 34.2 A, b = 34.8 A, and c = 99.4 A. One asymmetric unit contains one molecule of the pigeon lysozyme. The crystals diffract X-rays at least to 2.0 A resolution and are suitable for high resolution structure analysis. The diffraction data up to 3.0 A resolution were collected with a diffraction image processor, DIP100, using a Fuji imaging plate as an area detector. The structure was solved by the molecular replacement technique and refined to an R factor of 0.216. Least-squares fitting of the main-chains of pigeon egg-white lysozyme with those of chicken egg-white lysozyme and baboon alpha-lactalbumin showed that the main-chain folding of pigeon lysozyme is more similar to that of chicken lysozyme than that of alpha-lactalbumin. The largest differences between the pigeon and chicken lysozymes are in the surface loop regions.
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PMID:Crystallization and preliminary X-ray structure analysis of pigeon egg-white lysozyme. 160 55

Exons of eukaryotic genes that encode proteins frequently appear to encode structural and/or functional protein units [Gilbert, W. (1978) Nature (London) 271, 501; Blake, C.C.F. (1979) Nature (London) 277, 598]. alpha-Lactalbumin and c-type lysozyme are functionally quite different but structurally highly homologous proteins. Their gene organizations have been shown to be virtually the same and their exon structures are identical. The exon 2 region of hen lysozyme contains most of the amino acid residues that make up its catalytic cleft. In this study, we engineered a hybrid protein in which the exon 2 region of goat alpha-lactalbumin was replaced with that of hen lysozyme. This conferred catalytic activity on the alpha-lactalbumin, which is a nonenzymatic protein in its native structural form.
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PMID:Functional conversion of the homologous proteins alpha-lactalbumin and lysozyme by exon exchange. 163 Oct 69


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