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)

The self-mouse lysozyme peptide corresponding to residues 46-62 (ML46-62) binds to the major histocompatibility complex (MHC) class II molecules I-A(k) and it selectively inhibits, when coinjected with antigen, priming of I-A(k)-restricted, antigen-specific T cells. We demonstrate that administration of ML46-62 also inhibits in vivo antibody responses induced by I-A(k)-restricted T helper cells. ML46-62 is able to prevent the primary anti-hen egg white lysozyme (HEL) antibody response induced by the entire HEL molecule in B10.A(4R) mice, expressing only I-A(k) molecules, but not in mice of H-2d haplotype. ML46-62 also strongly decreases, in B10.A(4R) mice, the antibody response to ribonuclease A, a protein antigen unrelated to the MHC blocker, indicating that MHC blockade is the mechanism leading to inhibition of antibody response. This is further supported by the concomitant decrease, in vivo, of complex formation between immunodominant HEL peptides and I-A(k) molecules, preventing I-A(k)-restricted T cell induction. Administration of ML46-62 after antigen priming does not affect ongoing antibody responses, as expected from MHC blockade. A single injection of ML46-62 at the time of protein antigen priming precludes not only the primary, but also the secondary antibody response to a subsequent challenge with soluble protein, even when the challenge is performed several months after priming. Coinjection of antigen and MHC antagonist inhibits production of all antibody isotypes equally well, suggesting that MHC class II blockade affects both Th1- and Th2-type T helper cells. Therefore, these results indicate that administration of MHC class II-binding peptides can efficiently and selectively prevent the induction of T cell-dependent primary and secondary in vivo antibody responses by blocking antigen presentation to class II-restricted T helper cells.
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PMID:Selective immunosuppression by administration of major histocompatibility complex class II-binding peptides. II. Preventive inhibition of primary and secondary in vivo antibody responses. 847 15

Absolute values of heat capacity for some hydrated globular proteins (11S globulin, ovalbumin, ribonuclease A, and lysozyme) have been studied by differential scanning calorimetry. It has been found that for proteins with bound water, as in the case of protein solutions, the heat capacity of denatured proteins is higher then prior to denaturation. Depending on temperature and humidity, the denatured proteins can be either in high-elastic or glass state. Specific heat capacities for these two states have the same values for all proteins and depend only on temperature with a characteristic increment of 0.55 J.g-1.K-1 at glass transition. The glass transitions were observed not only in denatured but also in native proteins. Our results indicate that the main contribution to the heat capacity increment at denaturation is connected with the thermal motion in the protein globule, which is contrast with the commonly accepted ideas.
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PMID:[Heat capacity of hydrated and dehydrated globular proteins. The denaturing increment of heat capacity]. 848 67

The translational friction coefficients and intrinsic viscosities of four proteins (ribonuclease A, lysozyme, myoglobin, and chymotrypsinogen A) are calculated using atomic-level structural details. Inclusion of a 0.9-A-thick hydration shell allows calculated results for both hydrodynamic properties of each protein to reproduce experimental data. The use of detailed protein structures is made possible by relating translational friction and intrinsic viscosity to capacitance and polarizability, which can be calculated easily. The 0.9-A hydration shell corresponds to a hydration level of 0.3-0.4 g water/g protein. Hydration levels within this narrow range are also found by a number of other techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, calorimetry, and computer simulation. The use of detailed protein structures in predicting hydrodynamic properties thus allows hydrodynamic measurement to join the other techniques in leading to a unified picture of protein hydration. In contrast, earlier interpretations of hydrodynamic data based on modeling proteins as ellipsoids gave hydration levels that varied widely from protein to protein and thus challenged the existence of a unified picture of protein hydration.
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PMID:Calculation of translational friction and intrinsic viscosity. II. Application to globular proteins. 859 37

The apparent change in heat capacity, delta C(p), accompanying the thermally induced unfolding of lysozyme and of ribonuclease A was determined by means of differential scanning calorimetry in dilute aqueous buffer containing one of the following added solutes: 0.5 M or 1.0 M sucrose, 1.0 M glycine, 0.5 M, 1.0 M, or 2.0 M guanidinium chloride, 10% glycerol, or 0.5 M NaCl over a pH range. In each system the temperature of half-completion, t1/2, of the unfolding transition was varied by varying the pH. The resulting enthalpies of denaturation were linearly dependent on t1/2 for each solvent system. The resulting values of delta C(p) for each protein showed variation of almost 2-fold. Such large variations in the sensitivity of the proteins to temperature changes are not readily interpreted.
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PMID:The observed change in heat capacity accompanying the thermal unfolding of proteins depends on the composition of the solution and on the method employed to change the temperature of unfolding. 860 46

Protein disulfide isomerase has broad specificity in the catalysis of the formation and rearrangement of native disulfide bonds in proteins. This enzyme has two independent thioredoxin-like active sites (-CGHC-) and a peptide binding site. However, the mechanisms involving the catalytic processes are not clearly understood. It was reported that the enzyme associates with scrambled pancreatic ribonuclease A in vitro, and with misfolded human lysozyme in vivo. In the present study, recombinant human interleukin 2 has been chosen to probe the reaction intermediate in the reaction with the enzyme. We have identified and characterized a covalent associate formed in vitro by SDS-PAGE and Western blot analysis. This associate has a molecular weight of 71-72 kDa, the approximate sum of the molecular weights of the enzyme and the substrate. Western blot analysis confirmed that it formed via an intermolecular disulfide bond. Upon treatment with 2-mercaptoethanol, this bond was cleaved.
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PMID:Covalent association of protein disulfide isomerase with recombinant human interleukin 2 in vitro. 866 Mar 62

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

Renin can be detected in cardiovascular and other tissues but it disappears after bilateral nephrectomy indicating that tissues can take up or bind renal renin from the circulation. If renin uptake is the result of specific binding, plasma prorenin may be a natural antagonist of tissue directed renin-angiotensin systems. To investigate if specific prorenin/renin uptake occurs in rat tissues, binding studies were performed, with rat microsomal membrane preparations using recombinant rat prorenin metabolically labeled with 35S-methionine as a probe. A high affinity binding site for both renin and prorenin was identified. Affinities for prorenin and renin were approximately 200 and 900 pmol/L, respectively. Binding was reversible, saturable, and pH and temperature dependent. The relative binding capacities of membranes from various rat tissues were as follows (fmol/mg): renal cortex (55), liver (54), testis (63), lung (31), brain (18), renal medulla (15), adrenal (17), aorta (7), heart (4), and skeletal muscle (1). Bound prorenin was displaced by rat and human renin or prorenin but not by the prosequence of rat prorenin, angiotensin I or II, rat or human angiotensinogen, the renin inhibitor SQ30697, atrial natriuretic factor, amylase, insulin, bovine serum albumin, hemoglobin, heparin, lysozyme, ovalbumin, cytochrome C, pepsin, pepsinogen, ribonuclease A, mannose-6-phosphate, alpha-methyl mannoside, gonadotropin releasing hormone, or an antibody to hog renin binding protein. these results demonstrate specific binding of prorenin to a site in rat tissues, herein named ProBP, that also binds renin. It is possible that differences in prorenin/renin binding capacity determine the activity of tissue-directed renin-angiotensin systems and that prorenin is a natural antagonist. Alternatively, a prorenin/renin receptor may have been identified that may function by transducing an intracellular signal.
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PMID:Specific prorenin/renin binding (ProBP). Identification and characterization of a novel membrane site. 873 81

Because of its ability to probe directly the chiral elements of the peptide backbone, together with the very short time scale of the scattering process, vibrational Raman optical activity (ROA) can provide new information on structure in non-native states of proteins. Here we report ROA studies of hen egg white lysozyme and bovine ribonuclease A in unfolded denatured states, prepared by reducing all the disulfide bonds. ROA spectra of unfolded lysozyme at 45, 20, and 2 degrees C, and of unfolded ribonuclease A at 35 and 20 degrees C, are presented and discussed. At 45 and 20 degrees C, unfolded lysozyme appears to contain very little extended secondary structure, but at 2 degrees C there could be roughly 20% of the native amount of alpha-helix present but little beta-sheet. Unfolded ribonuclease A, on the other hand, appears to contain roughly 50% of its native-like secondary structure, including both alpha-helix and beta-sheet, at 20 degrees C; similar secondary structure persists at 35 degrees C, but the amount is reduced. The most striking result is the observation of three sharp ROA bands in the extended amide III region, originating in coupled C alpha-H and N-H deformations, which might monitor directly the dominant intrinsic propensities for residues to adopt particular phi, psi angles, averaged over the different amino acids in the mobile heteropolypeptide. Specifically, positive bands at approximately 1300 and 1314 cm-1 appear to monitor propensities for alpha-helix and beta-structure, respectively, and a negative band at approximately 1237 cm-1 appears to monitor that for the poly(L-proline) II helix. These signals are generated by individual residues clustering in the most favorable regions of the Ramachandran plot and are present even in the absence of signals from the corresponding extended secondary structures. At 45 degrees C, the 1300 and 1314 cm-1 ROA bands of unfolded lysozyme coalesce into a single sharp band from which an analysis similar to that used for exchange effects in NMR suggests a rate of approximately 2.6 x 10(12) s-1 for interconversion between the individual residue conformations at this temperature.
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PMID:Residual structure in unfolded proteins revealed by Raman optical activity. 882 88

The effect of 2,2,2-trifluoroethanol (TFE) on the structure of an all beta-sheet protein, cardiotoxin analogue 111 (CTX III) from the Taiwan cobra (Naja naja atra) is studied. It is found that high concentrations (> 80% v/v) of TFE induced a beta-sheet to alpha-helix structural transition. It is found that in denatured and reduced CTX III (rCTX III) helical conformation is induced even upon addition of low concentrations (> 10% v/v) of TFE. Using three other proteins, namely, ribonuclease A (RNase A), lysozyme and alpha-lactalbumin, it is been observed that helix-induction by TFE is intricately linked to drastic destabilization of native tertiary structural interactions in the proteins.
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PMID:Destabilisation of native tertiary structural interactions is linked to helix-induction by 2,2,2-trifluoroethanol in proteins. 902 98

After the recent discovery of a ribonuclease A unfolding intermediate [Kiefhaber, T., et al. (1995) Nature 375, 513-515], we investigated the unfolding pathway of hen egg white lysozyme. At pH* 4.00 with D2O at 10 degrees C and 6 M guanidinium chloride, unfolding shows a single, slow kinetic phase, with a relaxation time of 3300 s when monitored by circular dichroism (CD). Exchange of the tryptophan indole nitrogen protons shows that buried Trp residues 123, 111, and 108 lose tight packing and become solvent-exposed simultaneously, with a mean relaxation time of 3300 s, similar to the CD-monitored unfolding rate. Unfolding monitored by Trp fluorescence shows, moreover, that 90% of the amplitude change occurs in a slow phase, with a relaxation time of 2400 s. Faster-unfolding phases with minor amplitudes are detected by Trp indole hydrogen exchange and by fluorescence. It is likely that these changes are caused by Trp 62 and Trp 63, active site residues which are not buried in the hydrophobic core. Lysozyme unfolding was further monitored by the histidine 15 C epsilon1 proton, which gives resolved lines for the native and unfolded species in one-dimensional 1H-NMR spectra. The majority of the unfolding reaction, 70%, occurs in a slow phase with a relaxation time of 3600 s, but there is also a rapid unfolding phase; 30% of the His 15 C epsilon1 proton resonance intensity is found at the unfolded chemical shift within tens of seconds after the start of unfolding. The amplitude of the rapid unfolding phase increases proportionally with the concentration of GdmCl denaturant present. These results show that a partially buried residue of lysozyme, histidine 15, takes part in forming an unfolding intermediate similar to the one observed earlier for valine 63 in ribonuclease A. The tryptophan side chains buried in the hydrophobic core of lysoyzme, in contrast, do not participate in forming the unfolding intermediate, as judged by proton chemical shifts. The buried tryptophan residues of dihydrofolate reductase, monitored by 19F-NMR, do participate in forming an unfolding intermediate [Hoeltzli, S. D., & Frieden, C. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 9318-9322]; the difference between that study and ours may reside in the greater sensitivity of 19F to the detection of motional differences.
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PMID:Characterization of the unfolding pathway of hen egg white lysozyme. 906 98


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