Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The dependence of secondary structure on SS content was examined to gain further insight into the role of SS bond formation in chain folding. Lysozyme was reduced to various levels, and the products were studied with respect to remaining native structure. Reductions were carried out in the absence of denaturant. Thus, the observed changes were not attributable to a general denaturing effect, but more specifically to cleavage of SS bonds. The products of reduction were found by gel filtration chromatography to contain both polymeric and monomeric forms. By "fingerprinting", the monomers gave no indication of having undergone SS interchange, and specific cleavage of native SS bonds was indicated by a stepwise disappearance of SS-containing peptides with increasing reduction level. Ion-exchange chromatography of the carboxymethylated monomers gave the three possible reduction intermediates, containing two, four, and six carboxymethylcysteine residues per mole, in addition to the fully reduced form. The intermediates exhibited circular dichroic (CD) characteristics that were clearly nonnative, indicating alteration of the secondary structure throughout all stages of reduction. Concomitantly, there were extensive losses of enzymatic activity at intermediate levels, while no activity was found for the fully reduced form. Partially and fully reduced lysozymes were also examined for their abilities to resume native secondary structure in the absence of SS formation, as would be evidenced by a reversion to native CD characteristics. Despite literature indications of native structure in the reduced protein as observed from examination of CD behavior, none was found in the present effort, under a variety of experimental conditions. These observations are consistent with an essential role of SS bonds in forming and maintaining a major portion of the native secondary structure in lysozyme.
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PMID:Studies on the relationship of disulfide bonds to the formation and maintenance of secondary structure in chicken egg white lysozyme. 707 66

An improved iterative method for computing association constants from sedimentation equilibrium results obtained with self-interacting protein systems is presented which accounts for the composition-dependence of the activity coefficients of all oligomeric species. The method is based on the calculation of viral coefficients from covolume and charge considerations, the statistical mechanical basis of which is discussed in relation to the DLVO theory. The method is applied to results obtained with lysozyme in diethylbarbiturate buffer of pH 8.0 and ionic strength 0.15 at 15 degrees C. It is shown that these results, encompassing a range of total solute concentration up to 19.7 g/liter are consistent with self-association patterns comprising either a monomer--dimer--trimer system or an isodesmic indefinite self-association of the monomer, the latter being favored. A firmer distinction between these possibilities is sought on the basis of the dependence of the weight-average partition coefficient, determined by frontal gel chromatography, on total solute concentration (up to 56.6/liter). This analysis accounts for the composition-dependence of the ratio of the activity coefficients of partitioning monomer in mobile and stationary phases. It is concluded that all results are consistent with an indefinite self-association of lysozyme governed by a single association constant of 4.61 x 10(2) liter/mole.
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PMID:The indefinite self-association of lysozyme: consideration of composition-dependent activity coefficients. 718 65

This investigation examined the concept that arachidonic acid (AA) serves as a second messenger in stimulation of the respiratory burst and degranulation of polymorphonuclear neutrophils (PMN). The main support for this idea is from observations that reagent AA, added to cell suspensions, stimulates the respiratory burst and degranulation and these events are blocked by PLA2 inhibitors. We verified that exogenously-added AA stimulated release of O2-, myeloperoxidase (MPO), and lysozyme (LZ), but this required amounts of AA which approximated the critical micellar concentration. This suggested that such administration of AA might act as an extracellular agonist, similar to particulate stimuli, rather than acting as a second messenger as might occur following mobilization of AA from cellular membranes. To investigate the role of fatty acids released by hydrolysis of cellular phospholipids, exogenously-added group I, II or III PLA2's were used to mobilize fatty acids from cellular membranes. Mole quantities of cell-associated free fatty acids were measured by negative ion chemical ionization gas chromatography/mass spectrometry. AA mobilization in response to exogenous PLA2 was dose- (0.1 to 10 U/ml PLA2) and time-dependent (peak at 1 to 2 min with a reduction by 4 min). Resting neutrophils contained < 10 pmol free AA/10(7) PMN; the receptor-mediated agonist N-formyl-methionyl-leucyl-phenylalanine (fMLP) alone did not increase these values. Exogenously-added PLA2 generated large quantities of free AA in control and fMLP-treated cells (462 +/- 122 and 2097 +/- 176 pmol/10(7) PMN, respectively); however, this did not induce O2-, nor did it augment the level of O2- stimulated by fMLP. Also, PLA2 caused no degranulation and did not alter degranulation induced by fMLP. PLA2 also did not alter O2- or degranulation responses in primed PMN. The data indicate that mobilization of AA from cellular phospholipids neither stimulates nor modulates the respiratory burst or degranulation of PMN.
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PMID:Neutrophil release of arachidonic acid, oxidants, and proteinases: causally related or independent. 754 76

Halo nevi are characterized by progressive degeneration of nevus cells surrounded by a mononuclear cell infiltrate. We studied the morphological features of the nevus cells and the composition of the mononuclear cell infiltrate in 15 cases of halo nevi using immunohistochemical techniques and a battery of antibodies to different subsets of lymphocytes and histiocytes. Regression could be divided into four more or less identifiable stages, associated with different subsets of lymphocytes and monocyte-macrophage lineage cells. Stage I (preregression): nests of unremarkable nevus cells were surrounded by a moderate number of T lymphocytes (relatively small percentage of helper inducer T cells), occasional B cells and macrophages. Stage II (early regression): large number of T lymphocytes and FXIIIa-positive cells were in close contact with nevus cell clusters which showed ragged edges. Lysozyme-positive cells and epidermal Langerhans cells were mildly increased. Stage III (late regression): single nevomelanocytes showing mild atypia were present. Numerous T lymphocytes and macrophages positive for lysozyme, KP1 and/or FXIIIa were interspersed between the nevus cells. Increased numbers of epidermal Langerhans cells were present. Stage IV (complete regression): no nevus cells were observed and moderate numbers of T lymphocytes only remained. These results suggest that T cells, especially T-suppressor cells, and different subsets of macrophages participate in the regression of the nevi.
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PMID:Characterization of the mononuclear infiltrate involved in regression of halo nevi. 779 86

The adsorption isotherms of different proteins from aqueous solution to the surface of different solids have been compared in the presence of additives such as urea, surfactants and high concentration of various neutral salts. The adsorption isotherms of lysozyme on alumina are not affected much in the presence of 8 M urea showing the rigid structure of lysozyme whereas isotherms of hemoglobin show surface coagulation even in presence of 2 M urea. In presence of 8 M urea, adsorption isotherms of BSA on alumina show two distinct steps. The extent of protein adsorption in the presence of surfactants depends on the nature of surfactants as well as of the underlying surface. The adsorption isotherms of BSA and lysozyme in presence of 2 M concentration of different neutral salts have also been compared with each other. In the presence of denaturants such as NaI and LiCl, the proteins are adsorbed in unfolded beta-conformation whereas in the presence of protein stabilizers such as NaCl, KCl and Na2SO4, amount of protein adsorbed at saturation is zero or extremely small showing that unfolding of proteins at the interface is necessary for initial stage of protein adsorption. The standard free energy change (delta G degrees) per square meter of the surface, signifying relative affinity of adsorption at the state of monolayer saturation, have been calculated. The magnitude of standard free energy of transfer (delta G degrees B) of one mole of protein to the surface in presence of all the additives was found close to 40 kJ/mole.
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PMID:Effect of denaturants and stabilisers on protein adsorption at solid-liquid interfaces. 792 31

The cationic protein, lysozyme, is present in cartilage but its precise role in this tissue has not yet been established. This study shows that two major and structurally similar glycosaminoglycans (GAGs) of cartilage, i.e., chondroitin sulfate (CS) and hyaluronan (HA) interact with lysozyme at salt concentrations up to 40 mM. Such a low salt concentration is likely to occur in cartilage due to exclusion of microions by the high charge density of the proteoglycans (PGs). The affinity of binding to lysozyme increases with increasing molecular weight of HA and is higher for HA (Kd = 1-2 x 10(-8) M and 0.5-1 x 10(-7) M for HA of relative molecular mass of 4 x 10(5) and 5 x 10(4), respectively) than for CS (Kd = 1 x 10(-6) M). The binding displays optimal levels at around 20 mM but decreases at both lower and higher salt concentrations. This dependence of binding on salt concentration resembles that of the enzymic activity of lysozyme for its natural substrate, murein, which is structurally similar to HA/CS. The increase in binding up to 20 mM salt is characteristic for HA/CS-lysozyme interaction as such an effect was not observed in the interaction of heparin with lysozyme or of GAGs with serum albumin. Binding of HA to lysozyme was inhibited by various polyanions but not by uncharged macromolecules, indicating the electrostatic nature of the interaction. The dependence of binding on salt concentration obtained in systems where lysozyme is linked to an agarose support and the GAG is free in solution is similar to that determined when both macromolecules are free in solution; however, the number of GAG disaccharides bound per mole lysozyme increases significantly in the latter system, indicating a marked artifactual steric hindrance effect in the former.
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PMID:Binding properties of glycosaminoglycans to lysozyme--effect of salt and molecular weight. 816 Dec

The capacity of bovine serum amineoxidase (SAO) to oxidize free amino groups of nonconventional substrates, such as polylysine (up to 50 kDa) and some proteins as lysozyme and ribonuclease A, is described. The oxidation was quantified from the amount of H2O2 and NH3 enzymatically produced by SAO. Kinetic analysis indicated a stereospecific preference for L-configuration. Maximal oxidation rate was obtained with poly-L-lysine (9.6 kDa). After 10 h of incubation at 37 degrees C, the poly-L-lysine was partially oxidized generating 1.5 moles of H2O2 by one mole of polylysine. Denatured SAO presented very low oxidation rates with the mentioned substrates.
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PMID:Extended substrate specificity of serum amine oxidase: possible involvement in protein posttranslational modification. 866 Mar 85

Two different theories based on a multiple equilibrium model for analysing the binding data for ionic surfactant-protein interactions are investigated and modified, and intrinsic and statistical Gibbs free energies of binding per mole of surfactant are estimated. The characterization of the two models and interpretation of the binding process in terms of intrinsic and statistical binding free energies are discussed. These theories are applied to analysis of sodium n-dodecyl sulfate binding to ribonuclease A and lysozyme. Copyright 1997Academic Press
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PMID:Statistical Effects of the Binding of Ionic Surfactant to Protein 936 64

Interaction between protein disulfide isomerase, possessing not only isomerase but also chaperone-like activity, and olygomeric enzyme, GAPDH, has been studied using technique of immobilization on insoluble support. PDI dimers bound to CNBr-activated Sepharose were shown to possess high TPOR activity as well as the ability to reactivate lysozyme. Immobilized PDI was not found to interact neither with soluble tetrameric GAPDH, nor with soluble denatured GAPDH. However, soluble PDI binds effectively to immobilized GAPDH monomers; Kd was found to be 3.7 x 10(-6) M, stoichiometry 0.824 mole PDI monomers per mole GAPDH monomers. Immobilized GAPDH tetramers do not interact with PDI. These observations are also confirmed by the data on electrophoresis of proteins bound to immobilized GAPDH monomers and tetramers. The ability of PDI to interact with denatured protein form, but not with the native one, is considered to be evidence of chaperone-like activity of the enzyme.
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PMID:Study on the interactions between protein disulfide isomerase and target proteins, using immobilization on solid support. 959 88

The change in free energy of binding of hen egg white lysozyme (HEL) to the antibody HyHel-10 arising from ten point mutations in HEL (D101K, D101G, K96M, K97D, K97G, K97G, R21E, R21K, W62Y, and W63Y) was calculated using a combination of the finite difference Poisson-Boltzmann method for the electrostatic contribution, a solvent accessible surface area term for the non-polar contribution, and rotamer counting for the sidechain entropy contribution. Comparison of experimental and calculated results indicate that because of pKa shifts in some of the mutated residues, primarily those involving Aspartate or Glutamate, proton uptake or release occurs in binding. When this effect was incorporated into the binding free energy calculations, the agreement with experiment improved significantly, and resulted in a mean error of about 1.9 kcal/mole. Thus these calculations predict that there should be a significant pH dependence to the change in binding caused by these mutations. The other major contributions to binding energy changes comes from solvation and charge charge interactions, which tend to oppose each other. Smaller contributions come from nonpolar interactions and sidechain entropy changes. The structures of the HyHel-10-HEL complexes with mutant HEL were obtained by modeling, and the effect of the modeled structure on the calculations was also examined. "Knowledge based" modeling and automatic generation of models using molecular mechanics produced comparable results.
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PMID:Calculation of HyHel10-lysozyme binding free energy changes: effect of ten point mutations. 974 43


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