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)

Four different disulfide bridges (linking positions 9-164, 21-142, 90-122, and 127-154) were introduced into a cysteine-free phage T4 lysozyme at sites suggested by theoretical calculations and computer modeling. The new cysteines spontaneously formed disulfide bonds on exposure to air in vitro. In all cases the oxidized (crosslinked) lysozyme was more stable than the corresponding reduced (noncrosslinked) enzyme toward thermal denaturation. Relative to wild-type lysozyme, the melting temperatures of the 9-164 and 21-142 disulfide mutants were increased by 6.4 degrees C and 11.0 degrees C, whereas the other two mutants were either less stable or equally stable. Measurement of the equilibrium constants for the reduction of the engineered disulfide bonds by dithiothreitol indicates that the less thermostable mutants tend to have a less favorable crosslink in the native structure. The two disulfide bridges that are most effective in increasing the stability of T4 lysozyme have, in common, a large loop size and a location that includes a flexible part of the molecule. The results suggest that stabilization due to the effect of the crosslink on the entropy of the unfolded polypeptide is offset by the strain energy associated with formation of the disulfide bond in the folded protein. The design of disulfide bridges is discussed in terms of protein flexibility.
...
PMID:Stabilization of phage T4 lysozyme by engineered disulfide bonds. 267 95

The three-dimensional structure of a protein is governed by the thermodynamical principle established experimentally by Anfinsen, Isemura, and others. The rapidity of the folding process is another important key phenomenon. With these basics in mind an island model is proposed which requires a restricted folding pathway. A physicochemical method of the prediction of alpha-helices and beta-strands is also discussed. By virtue of the long-range hydrophobic interaction and the specific interactions between hydrophobic residues which are determined by the basic idea underlying the island model, one can fold the polypeptide chain into a tertiary structure upon determination of the secondary structures. Several examples of folding are presented. In myoglobin the heme group must be considered to reach the correct final tertiary structure. In lysozyme and phospholipase, the disulfide bondings are necessary to fasten the polypeptide chain. The selection of proper cysteine pairs among other possible ones is carried out by drawing the lampshades (locus of H atom of SH) of cysteines. In flavodoxin and thioredoxin the formation of parallel beta-structure from beta-strands is considered. The formations of antiparallel beta-structure in lysozyme and phospholipase are also discussed.
...
PMID:Principles of protein architecture. 269 41

The electrophoretic pattern of cysteine proteinases in axenically grown myxamoebae of Dictyostelium discoideum can be altered by the addition of either Gram-negative (Klebsiella aerogenes, Escherichia coli) or Gram-positive (Micrococcus lysodeikticus, Bacillus subtilis) bacteria to the culture. No changes occurred, however, if either yeast or latex beads were used in place of bacteria. The changes involved the simultaneous loss of proteinases characteristic of the axenic cells (the A-forms) and the acquisition of those found in cells which have been grown on bacteria (the B-forms). Using K. aerogenes the conversion was complete within 4 h. Extracellular proteinase activity was unaffected during this period. After the D. discoideum cells had been lysed, no equivalent change in proteinase band pattern could be produced either by prolonged incubation of cell extracts or by treatment with proteinases. An identical conversion could be induced in cultures of myxamoebae by a factor, cysteine proteinase converting factor (CPCF), present in the 15,000 g supernatant of a sonicated suspension of K. aerogenes. CPCF was macromolecular, as demonstrated by both ultrafiltration and gel filtration, acid-precipitable, but was soluble in ethanol or alkali. Its activity was unaffected by treatment with trypsin. The results suggested that CPCF might be a component of the bacterial cell wall, and since its activity was affected by lysozyme treatment, peptidoglycan is implicated. The results can be interpreted in terms of a novel nutrient-dependent post-translational change which affected most of the cysteine proteinases present in D. discoideum myxamoebae.
...
PMID:A bacterial factor induces changes in cysteine proteinase forms in the cellular slime mould Dictyostelium discoideum. 305 31

Reorganization and activation energies for charge transfer reactions occurring inside a dielectric sphere have been calculated by solving the problem of polar medium reorganization within and outside a dielectric sphere placed in another infinite dielectric. The dielectric sphere is assumed to simulate a protein globule, i.e. an enzyme molecule. It has been shown that for some reaction types the activation energy tends to decrease as the globule radius increases and that for each of the reaction types considered there is an optimal globule radius an increase of which does not bring about any tangible activation energy reduction. The calculated optimal radii for different processes are in good agreement with the increasing molecular sizes in the series: ribonuclease less than or equal to lysozyme less than serine proteinases approximately equal to cysteine proteinases less than NAD-dependent dehydrogenases. The calculated radii are usually about 1.5 to 1.7 times (and molecular masses about 4-5 times) smaller than the experimental ones. The reasons for this discrepancy are discussed and it has been suggested that the approximate nature of the treatment of a protein globule as a structureless dielectric is the main reason. It is shown that charge transfer at an acute angle to the globule surface is the optimum process. For endoergonic reaction stages it is the net charge transfer towards the periphery and for exoergonic ones that in the reverse direction which are advantageous. These conclusions are consistent with the data about the structure of the above-mentioned enzymes.
...
PMID:Medium reorganization energy and enzymatic reaction activation energy. 315 27

Triplet-state energies, zero-field splittings (ZFS), and total decay rate constants of the individual triplet-state sublevels of the tryptophan (Trp) residues located at positions 126, 138, and 158 in bacteriophage T4 lysozyme have been determined by using low-temperature phosphorescence and optical detection of magnetic resonance spectroscopy in zero applied magnetic field. An investigation of spectral and kinetic properties of individual Trp residues was facilitated by measurements on point-mutated proteins containing two Trp----Tyr substitutions. We find that the phosphorescence lifetime of the buried Trp-138 is considerably shorter than those of the solvent-exposed Trp residues. CH3HgII binding to cysteine residues in T4 lysozyme selectively perturbs the triplet state of Trp-158 by means of an external heavy-atom effect. In contrast with the previous observation of selective x-sublevel perturbation in the Trp-CH3Hg complex, the radiative character of the z sublevel (z is the out-of-plane axis) is selectively enhanced due to the heavy-atom perturbation of Trp-158. The observed pattern of radiative and total sublevel decay constants of the perturbed Trp is attributed to a special orientation of the Hg atom with respect to the indole plane.
...
PMID:Comparative triplet-state properties of the three tryptophan residues in bacteriophage T4 lysozyme and in the enzyme complex with methylmercury(II). 320 14

Salivary proteins adsorbed to powdered enamel and cementum from parotid and submandibular saliva (1:1) of caries-resistant (CR) and caries-susceptible (CS) subjects were examined qualitatively by polyacrylamide disc electrophoresis and quantitatively by immunochemical procedures. The electrophoretic patterns showed no consistent difference between enamel and cementum or between CR and CS samples. Quantitatively, there were no significant differences between CR and CS samples, but significant differences between enamel and cementum. On the basis of ng/mm2, enamel adsorbed five times as much acidic proline-rich protein and cysteine-containing protein as cementum and nearly twice as much lysozyme. There were no significant differences in adsorption of albumin and lactoferrin. The lack of difference in the concentration of pellicle proteins in CR and CS subjects may be related to similar findings with parotid and submandibular saliva. The influence of the major differences in surface pellicle proteins between enamel and cementum on the properties of their respective pellicles is uncertain.
...
PMID:Quantitative immunochemistry of salivary proteins adsorbed in vitro to enamel and cementum from caries-resistant and caries-susceptible human adults. 346 84

Wild-type T4 lysozyme contains unpaired cysteine residues at positions 54 and 97. To investigate the role these residues play in the thermal inactivation of the wild-type, we constructed a double mutant with these cysteines replaced with valine and serine. This molecule, T4 lysozyme (C54V/C97S), is more stable than the wild-type to inactivation at 70 degrees C at pH 6.5 and 8.0. Guanidine hydrochloride reactivation experiments and SDS-PAGE on the inactivated products show that the wild-type is susceptible to varying degrees of oxidative damage, depending on buffer conditions, while the cysteine-minus mutant inactivates only by other pathways. The products of thermal, oxidative inactivation of the wild-type are disulfide-linked oligomers. The dependence of inactivation rate on temperature suggests that the formation of these aggregates depends on prior thermal unfolding of the T4 lysozyme molecule.
...
PMID:The role of cysteine oxidation in the thermal inactivation of T4 lysozyme. 350 92

Five different cysteine-containing mutants of the lysozyme from bacteriophage T4 were used to explore the feasibility of using site-directed mutagenesis to generate isomorphous heavy-atom derivatives for protein crystallography. Cysteines 54 and 97, present in wild-type lysozyme, can be readily reacted with mercuric ion to produce an excellent isomorphous heavy-atom derivative. Mutants with an additional cysteine at position 86, 146, 153 or 157, or with Cys 97 replaced by Val, were engineered by site-directed mutagenesis. The mutant lysozyme Thr 157----Cys reacts with mercuric chloride to give an excellent new derivative although Cys 157 is only approximately 60% substituted with the heavy atom. The cysteine at position 146 is largely buried but reacts readily with mercuric chloride. In this case the isomorphism is poor and the resultant derivative is of marginal quality. Cys 153 reacts rapidly with mercuric ion but the derivative crystals do not diffract. The mutant Pro 86----Cys does not yield a particularly good heavy-atom derivative. This is due in part to a loss of isomorphism associated with the mutation. In addition, Cys 86 shows very little reactivity towards mercurials even though it is fully exposed to solvent. The mutation Cys 97----Val was used to explore the possibility of creating an independent derivative by deleting a heavy-atom site already present in wild-type lysozyme. In all cases that were tested, the quality of the heavy-atom derivative was improved by using as an isomorphous pair mercury-substituted mutant versus non-substituted mutant rather than mercury-substituted mutant versus (non-substituted) wild-type lysozyme.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Use of site-directed mutagenesis to obtain isomorphous heavy-atom derivatives for protein crystallography: cysteine-containing mutants of phage T4 lysozyme. 350 94

It was found that thioglycolic acid prevents destruction of tryptophan during rapid hydrolysis of protein with a trifluoroacetic acid/HCl mixture (1:2, v/v) at 166 degrees C for 25 or 50 min. The addition of 5% (v/v) thioglycolic acid gave the maximum tryptophan recovery (88.3%) for a 25-min hydrolysate of lysozyme. Tryptophan recoveries varied slightly among three different proteins; 88% for lysozyme, 73% for alpha-chymotrypsinogen A, and 85% for apomyoglobin. However, when extrapolated to zero time, the values were close to one another: 94, 87, and 88%, respectively. The addition of thioglycolic acid was also advantageous for recovering amino acids other than tryptophan. Particularly, yields of carboxymethylcysteine and methionine were greatly improved. This modified rapid hydrolysis method gave satisfactory results without the need for separate analyses of tryptophan and cysteine, provided proteins were reduced and carboxymethylated prior to hydrolysis.
...
PMID:Recovery of tryptophan from 25-minute acid hydrolysates of protein. 396 60

Legionella pneumophila and related species were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis for outer membrane proteins. Of the 10 species examined, 9 contained a 24-kilodalton (kDa) major outer membrane protein (MOMP) that was resolvable only when outer membrane material was heated in the presence of 2-mercaptoethanol. Labeling studies with [35S]cysteine indicated that the protein contained cysteine, and disulfide cross-linking of the unreduced complex was demonstrated by labeling with iodoacetamide. The unreduced outer membrane preparation contained peptidoglycan, and after treatment with lysozyme to remove peptidoglycan, a protein complex of 95 kDa was observed by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the absence of 2-mercaptoethanol. Reduction of the 95-kDa complex yielded 24-kDa monomers, suggesting that the 95-kDa complex was composed of four subunits. The 24-kDa MOMP from L. pneumophila was purified, and antibody produced to this protein cross-reacted with all species of Legionella as determined from an immunoblot of a sodium dodecyl sulfate gel. Only serogroup 1 strains of L. bozemanii lacked the 24-kDa MOMP and showed no cross-reactivity. These results suggest that the 24-kDa MOMP common to most species of Legionella contains a genus-specific epitope.
...
PMID:Disulfide-bonded outer membrane proteins in the genus Legionella. 398 79


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---