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)

It is not easy to find candidate sites within a given protein where the geometry of the polypeptide chain matches that of metal-binding sites in known protein structures. By choosing a location in T4 lysozyme that is inherently flexible, it was possible to engineer a two-histidine site that binds different divalent cations. Crystallographic analysis shows that the geometry of binding of zinc is distorted tetrahedral while that of cobalt and nickel is octahedral. Insofar as spectroscopic data can be measured, they indicate that similar modes of coordination are retained in solution. The two substitutions, Thr21 --> His and Thr142 --> His, lie, respectively, on the surface of the N- and C-terminal domains on opposite sides of the active site cleft. The design takes advantage of hinge-bending motion which allows the binding site to adapt to the most favorable ligand geometry for the metal. Introduction of the two histidines increases the melting temperature of the protein by 2.0 degrees C at pH 7.4. Metal binding further increases the melting temperature, but only by a small amount (up to 1.5 degrees C). A third substitution, Gln141 --> His, which could act as a third ligand in principle, does not do so, demonstrating the difficulty in mimicking naturally occurring metal-binding sites.
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PMID:Use of a non-rigid region in T4 lysozyme to design an adaptable metal-binding site. 1083 4

We carried out an immunotoxicological field study of wood mice in three populations along a heavy metal pollution gradient. Heavy metal concentrations in liver tissue indicated that exposure to silver, arsenic, cadmium, cobalt and lead decreased with increasing distance from a non-ferrous smelter. Host resistance to the endoparasite Heligmosomoides polygyrus decreased with increasing exposure, while the abundance of tick larvae and the nematode Syphacia stroma was unrelated to heavy metal exposure. Spleen mass was increased at the intermediate and the most polluted sites and was positively correlated with the number of H. polygyrus and tick larvae. Proportion of early apoptotic leukocytes increased towards the smelter and was positively related to cadmium exposure. Red and white blood cell counts and lysozyme activity showed no relationship with metal exposure. All together, our observations suggest negative effects of heavy metal exposure on the immune function of wood mice under field conditions.
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PMID:Immunotoxicology in wood mice along a heavy metal pollution gradient. 1532 54

Increasing evidence suggests that amyloid peptides associated with a variety of degenerative diseases induce neurotoxicity in their intermediate oligomeric state, rather than as monomers or fibrils. To test this hypothesis and investigate the possible involvement of Ca2+ signaling disruptions in amyloid-induced cytotoxicity, we made homogeneous preparations of disease-related amyloids (Abeta, prion, islet amyloid polypeptide, polyglutamine, and lysozyme) in various aggregation states and tested their actions on fluo-3-loaded SH-SY5Y cells. Application of oligomeric forms of all amyloids tested (0.6-6 microg ml-1) rapidly (approximately 5 s) elevated intracellular Ca2+, whereas equivalent amounts of monomers and fibrils did not. Ca2+ signals evoked by Abeta42 oligomers persisted after depletion of intracellular Ca2+ stores, and small signals remained in Ca2+-free medium, indicating contributions from both extracellular and intracellular Ca2+ sources. The increased membrane permeability to Ca2+ cannot be attributed to activation of endogenous Ca2+ channels, because responses were unaffected by the potent Ca2+-channel blocker cobalt (20 microm). Instead, observations that Abeta42 and other oligomers caused rapid cellular leakage of anionic fluorescent dyes point to a generalized increase in membrane permeability. The resulting unregulated flux of ions and molecules may provide a common mechanism for oligomer-mediated toxicity in many amyloidogenic diseases, with dysregulation of Ca2+ ions playing a crucial role because of their strong trans-membrane concentration gradient and involvement in cell dysfunction and death.
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PMID:Calcium dysregulation and membrane disruption as a ubiquitous neurotoxic mechanism of soluble amyloid oligomers. 1572 60

Metal binding to lysozyme has received wide interest. In particular, it is interesting that Ni2+, Mn2+, Co2+, and Yb3+ chloride salts induce an increase in the solubility of the tetragonal form in crystals of hen egg white lysozyme at high salt concentration, but that Mg2+ and Ca2+ chloride salts do not. To investigate the interactions of the di- and trivalent metal ions with the active site of lysozyme and compare the effects of the di- and trivalent metal ions on molecular conformation of lysozyme based on the structural analysis, the crystal structures of hen egg white lysozyme grown at pH 4.6, in the presence of 0.5 M MgCl2, CaCl2, NiCl2, MnCl2, CoCl2, and YbCl3, have been determined by X-ray crystallography at 1.58 A resolution. The crystals grown in these salts have an identical space group, P4(3)2(1)2. The molecules show no conformational changes, irrespective of the salts used. Ni2+ and Co2+ binding to the Odelta atom of Asp52 in the active site at 1.98 and 2.02 A, respectively, and Yb3+ binding to both the Odelta atom of Asp52 and the Odelta1 atom of Asn46 at 2.25 A have been identified. The binding sites of Mn2+, Mg2+, and Ca2+ have not been found from different Fourier electron density maps. The Ni2+ and Co2+ ions bind to the Odelta atom of Asp52 at almost the same position, while the Yb3+ ion takes a different position from the Ni2+ and Co2+ ions. On the other hand, the anion Cl-, interacting with the Oeta atom of Tyr23 at a site of about 2.90 A, has also been determined for each crystal.
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PMID:Structural details at active site of hen egg white lysozyme with di- and trivalent metal ions. 1613 73

This study was undertaken to examine physiological responses to acidification of environmental water in the "cobalt" variant of rainbow trout (Oncorhynchus mykiss), which exhibits malformation of the pituitary, by following changes in plasma levels of cortisol and electrolytes, blood pH, gill Na(+), K(+)-ATPase activity, and immune functions after exposure to acid water (pH 4.5). Resting levels of plasma cortisol and lysozyme were significantly lower in the cobalt variant than in the normal trout, whereas plasma ceruloplasmin was significantly higher in the cobalt variant, suggesting that some endocrine factors, lacking or deficient in the cobalt variant, are important for the regulation of its immune functions. Blood pH was slightly but significantly lower in the cobalt variant at rest. After exposure to acid water for 24 h, both the normal trout and cobalt variant showed a significant elevation in plasma cortisol, although the increased level in the cobalt variant was still lower than that in the normal trout transferred to neutral water. No differences were seen in blood pH, plasma electrolytes, and gill Na(+), K(+)-ATPase activity between the normal trout and the cobalt variant, indicating that the cobalt variant regulates ion balance when exposed to acid water, despite malformation of the pituitary. Although the normal trout showed a reduction in plasma lysozyme level after acid exposure, there was no significant change in the cobalt trout. Adverse effects of pituitary malformation on ion balance and immune functions may be compensated by extrapituitary factors in the cobalt variant when it is exposed to acid water.
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PMID:Effects of acid water exposure on plasma cortisol, ion balance, and immune functions in the "cobalt" variant of rainbow trout. 1697 89

Strong chiral discrimination and site-selective photocleavage of two model proteins, lysozyme and bovine serum albumin (BSA), by new pyrenyl probes are reported here. The enantiomeric pyrenyl probes D-phenylalanine-1(1-pyrene)methylamide (PMA- D-Phe) and L-phenylalanine-1(1-pyrene)methylamide (PMA- l-Phe) were synthesized by coupling the carboxyl function of D-phenylalanine or L-phenylalanine with the amino group of 1(1-pyrene)methylamine. Binding affinities of the two enantiomers with the proteins were quantitated in absorption titrations. BSA indicated 10-fold selectivity for PMA- D-Phe, and the binding constants for the L- and D-enantiomers were 3.8 x 10(5) and 4.0 x 10(6) M(-1), respectively. Lysozyme, similarly, indicated a 6-fold preference for PMA- D-Phe with binding constants of 3.3 x 10 (5) and 2.0 x 10(6) M(-1) for the L- and D-isomers, respectively. Such strong chiral discrimination illustrates the key role of the chiral center of the probe (Phe) in the binding interactions. The enantiomers were tested to examine how the chiral discrimination for their binding influences reactivity toward protein photocleavage. Irradiation of the probe-protein complexes, at 342 nm in the presence of hexammine cobalt(III) chloride, resulted in the cleavage of the protein backbone. Photocleavage did not proceed in the dark or in the absence of the pyrenyl probes. Both enantiomers indicated low reactivity with BSA (<5% yield), while large photocleavage yields ( approximately 57%) have been noted with lysozyme. This lysozyme photocleavage yield is a significant improvement over previous reports. However, both enantiomers cleaved lysozyme at the same location between Trp108-Val109, despite the strong chiral selectivity for binding. H-atom abstraction from Trp 108, accessible from the active site cleft, could initiate the observed peptide bond cleavage.
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PMID:Chiral protein scissors activated by light: recognition and protein photocleavage by a new pyrenyl probe. 1859 76

Photocleavage of chicken hen egg lysozyme by three Co(III)ammine complexes, hexamminecobalt(III) chloride ([Co(NH3)6]+3), pentamminechloro cobalt(III)chloride ([Co(NH3)5Cl]+2), and tetramminecarbonato cobalt(III) nitrate ([Co(NH3)4CO3]+), is reported here. Photocleavage resulted in two fragments of molecular masses of approximately 10.5 kDa and approximately 3.5 kDa which add-up to that of the parent molar mass. Detailed studies on the influence of irradiation time, excitation wavelength, the type of ligand coordinated to Co(III), concentration of the metal complex, the addition of competing metal ions, and quenchers on the protein photocleavage are reported. The Co(III) complexes also photocleaved apotransferrin, bovine serum albumin, and yeast enolase. Near-equimolar concentrations of Ni(II), Co(II) or Gd(III) inhibited the photocleavage, and therefore, binding of Co(III) metal complexes to Ni(II)/Co(II)/Gd(III) binding sites on lysozyme is necessary for the observed photocleavage. Since these ions are known to bind to Asp52 on lysozyme, we suspect that the above Co(III) complexes bind at this site, and initiate the protein cleavage. The Co(III) complexes have appropriate photochemical reactivities to cleave the peptide backbone, and they may be useful in the design of novel photochemical approaches to cleave the protein backbone.
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PMID:Inorganic photochemical protein scissors: photocleavage of lysozyme by Co(III) complexes. 1903 6

Steady-state and time-resolved studies of site-selective photocleavage of lysozyme by cobalt(III) complexes [Co(NH(3))(5)Br](2+) and ([Co(NH(3))(4)CO(3)](+) are reported. Photocleavage resulted in two fragments of molecular masses approximately 10.5 kDa and approximately 3.5 kDa, and the yield increased (8-33%) with irradiation time (0.16-0.8 h) as well as with the metal complex concentration (0.1-5 mM). The reaction proceeded to a significant extent even when nearly stoichiometric amounts of the reagents were used. Photocleavage was effective at wavelengths ranging from 310 to 390 nm, and cleavage was inhibited by the addition of selected metal ions such as Gd(III) at moderate concentrations (2 mM). Gd(III) is known to bind at Asp52/Glu35 residues on lysozyme, and these residues are located at the enzyme active site. Current and previous studies suggest that Co(III) metal complexes bind at this site on lysozyme. Consistent with this hypothesis, [Co(NH(3))(4)CO(3)](+) (8 mM) inhibited lysozyme activity by 67%. Laser flash photolysis studies show that excitation of the metal complexes [Co(NH(3))(5)Br](2+) and ([Co(NH(3))(4)CO(3)](+) (308 nm, 20 ns pulse width) resulted in the corresponding ligand-derived radical intermediates. For example, photoexcitation of an aqueous solution of [Co(NH(3))(5)Br](2+) at 308 nm resulted in the formation of Br(2)(-*). When the excitation was carried out in the presence of lysozyme, Br(2)(-*) was quenched with a bimolecular rate constant of 1.4 x 10(9) M(-1) s(-1). Quenching resulted in protein-derived radicals (Trp(+*) and Tyr(+*)), as identified by their characteristic known transient absorption bands. Steady-state studies correlated with the time-resolved data, and taken together, these illustrated the reactivities of Co(III) metal complexes to direct protein photocleavage with high selectivity.
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PMID:Steady-state and time-resolved studies of the photocleavage of lysozyme by Co(III) complexes. 1981 Jun 86

Cobalt(iii) complexes [Co(pnt)(B)(2)](NO(3))(2) (1-3) of pyridine-2-thiol (pnt) and phenanthroline bases (B), viz. 1,10-phenanthroline (phen in 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq in ) and dipyrido[3,2-a:2',3'-c]phenazine (dppz in 3), have been prepared, characterized and their photo-induced anaerobic DNA cleavage activity studied. The crystal structure of 1a as mixed ClO(4)(-) and PF(6)(-) salt of 1 shows a Co(III)N(5)S coordination geometry in which the pnt and phen showed N,S- and N,N-donor binding modes, respectively. The complexes exhibit Co(iii)/Co(ii) redox couple near -0.3 V (vs. SCE) in 20% DMF-Tris-HCl buffer having 0.1 M TBAP. The complexes show binding propensity to calf thymus DNA giving K(b) values within 2.2 x 10(4)-7.3 x 10(5) M(-1). Thermal melting and viscosity data suggest DNA surface and/or groove binding of the complexes. The complexes show significant anaerobic DNA cleavage activity in red light under argon atmosphere possibly involving sulfide anion radical or thiyl radical species. The DNA cleavage reaction under aerobic medium in red light is found to involve both singlet oxygen and hydroxyl radical pathways. The dppz complex shows non-specific BSA and lysozyme protein cleavage activity in UV-A light of 365 nm via both hydroxyl and singlet oxygen pathways. The dppz complex exhibits photocytotoxicity in HeLa cervical cancer cells giving IC(50) values of 767 nM and 19.38 microM in UV-A light of 365 nm and in the dark, respectively. A significant reduction of the dark toxicity of the dppz base (IC(50) = 8.34 microM in dark) is observed on binding to the cobalt(iii) center.
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PMID:Anaerobic DNA cleavage activity in red light and photocytotoxicity of (pyridine-2-thiol)cobalt(III) complexes of phenanthroline bases. 2044 26

A new approach for rapid and highly sensitive protein extraction using cobalt oxide nanoparticles modified with cetyltrimethylammonium (Co(3)O(4)/CTA(+) NP) using nanoparticle-based liquid-liquid microextraction (NP-LLME) coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been successfully demonstrated. For the first time, the metal oxide NPs (Co(3)O(4)/CTA(+) NP) prepared in the organic phase (toluene) have been successfully applied for the extraction and preconcentration of proteins from sample solutions and complex samples via electrostatic forces involved between the metal oxide NP and proteins. Lysozyme was used as the model protein to investigate the optimal extraction parameters of the current approach. The optimal conditions were obtained at pH > pI for 10 min of incubation time (extraction time) with 3% salt (NaCl) addition. The Co(3)O(4)/CTA(+) NP was successfully applied for the highly sensitive analysis of an array proteins such as insulin, chymotrypsinogen and lysozyme from aqueous solution, protein mixture and milk samples in nanoparticle-based liquid-phase microextraction coupled with MALDI-MS. The potentiality of the NP-LLME using Co(3)O(4)/CTA(+) NP for the extraction of proteins was also compared with other types of NP-liquid phase microextraction (LPME) methods. The current approach offers distinct advantages including rapidity, straightforwardness, high sensitivity for washing- and separation-free MALDI-MS analysis of proteins.
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PMID:Rapid and highly sensitive protein extraction via cobalt oxide nanoparticle-based liquid-liquid microextraction coupled with MALDI mass spectrometry. 2216 66


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