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)

Conformational studies on an isolated integral membrane protein are reported. Lipoprotein of Escherichia coli outer membrane was released from murein by treatment with either lysozyme or trypsin. The isolated lysozyme-released lipoprotein (lipoprotein I) contained 2 or 3 muropeptides covalently linked at the C-terminal end, while the trypsin-released lipoprotein (lipoprotein II) was free of muropeptides and lacked the C-terminal peptide Tyr-Arg-Lys. Circular dichroism spectra of the two preparations were essentially identical, and they show an alpha-helix content of about 80%. According to calculations based on the Chou-Fasman rules for proteins of known sequence, lipoprotein is 64% alpha-helix and 15% beta-structure. Infrared spectroscopy qualitatively supports these values. The conformation was stable in the pH range of 5 - 12. Danaturation of lipoprotein by heat, 8 M urea, or sodium dodecylsulphate was a fully reversible, cooperative process. The thermal denaturation of lipoprotein occurs in two steps with transition points at 79.4 degrees C for lipoprotein I and at 85.1 degrees C for lipoprotein II. Lioprotein markedly changes conformation at dodecylsulphate concentrations where micelle formation sets in. The unusual behaviour of the lipoprotein convormation in sodium dodecylsulphate is discussed in relation to the lipoprotein conformation and aggregation within the membrane.
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PMID:Conformational studies on murein-lipoprotein from the outer membrane of Escherichia coli. 79 57

In order to identify the functional groups which really contribute to the carbon dioxide gas adsorption by proteins, epsilon-amino groups of lysine residues of egg albumin were chemically modified with trinitrobenzene sulfonic acid to various degrees. About 60% of the total amount of carbon dioxide gas absorbed by solid egg albumin diminished by complete modification. The amount of carbon dioxide gas adsorbed by lysozyme, its hydrolyzates and gelatin hydrolyzates depended upon the lysine content, arginine content and average molecular weight. The good correlation was obtained between the amount of carbon dioxide gas absorbed and the total of lysine and arginine content of them. The ability of carbon dioxide gas adsorption by alpha-amino group of amino acids and oligopeptides was found to be developed by the elongation of the peptide chain of glycine and other amino acid, by the removal of alpha-carboxyl group of histidine and tyrosine to corresponding amines and by the esterification of alpha-carboxyl group of leucine with p-nitrophenol. These results clearly indicate that CO2 binding sites in protein in the gas-solid phase system are epsilon-amino, alpha-amino and guanidinium groups.
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PMID:Identification and properties of reactive sites in protein capable of binding carbon dioxide in a gas-solid phase system. 87 81

Two mutants of phage T4 lysozyme were prepared and characterized. One mutation substituted a tyrosine residue for tryptophan at position 138. The other substituted tyrosines at all three tryptophan positions of the wild type molecule (126, 138, 158). Comparative studies of the physical properties (absorption, fluorescence, circular dichroism) of the three enzymes were performed as a function of pH. Also, the proteins were reversibly melted as a function of pH. Since the unfolding reaction appeared to be a two-state process for all these proteins, the data were analyzed by the van 't Hoff procedure. The changes in stability and activity produced by substitution of Trp 138 were especially significant. The other substitutions were neutral. See the end of the paper for a summary of conclusions. In the appendix the appropriate thermodynamic relations are developed for a constant deltaCp transition.
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PMID:Stability of phage T4 lysozymes. I. Native properties and thermal stability of wild type and two mutant lysozymes. 91 78

Studies on the structure and substrate specificity of purified rat kidney nuclear (RKN) lysozyme are reported. The carboxyl and amino terminal residues of RKN-lysozyme were found to be leucine and alanine respectively. The amino acid composition indicated similarities and differences as compared with that of hen egg white (HEW) lysozyme. There were alterations in the nine amino acid residues, Lys, His, Arg, Asp, Glu, Pro, 1/2 Cys, Tyr and Trp. The other nine residues were present in identical proportions to those of HEW-lysozyme. The decrease in the arginine and aspartic acid residues was found to be compensated by the increase in the number of lysine, histidine and glutamic acid residues. The overall ratio of the acidic to basic amino acids has thus been conserved in the mammalian enzyme. In addition, RKN-lysozyme contained decreased numbers of Trp, Tyr and 1/2 Cys, and increased numbers of proline residues as found in HEW-lysozyme. RKN-lysozyme did not cross react with heterologous antibodies produced against HEW-lysozyme, and vice versa. RKN-lysozyme showed distinct specificity towards the lysis of M. luteus. Against this substrate, it was three times more efficient than HEW-lysozyme. It also cleaved E. coli B, but its efficiency was half as much as with M. luteus. However, it cleaved P. septica and B. subtilis at a rate similar to HEW-lysozyme under identical conditions.
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PMID:Structure-activity studies on mammalian tissue lytic enzymes: chemical characterization and substrate specificity of rat kidney nuclear lysozyme. 95 82

The reaction of iodine with aromatic residues of hen egg white lysozyme is examined by means of natural abundance 13C nuclear magnetic resonance spectroscopy. In the unfractionated product of the reaction at PH 5.5 (with I2/lysozyme molar ratios of 0.5, 1.0, and 2.5), the only detectably modified aromatic residues are Trp-108 and either Tyr-20 or Tyr-23 (probably the latter). The rates of reaction at the two sites are similar. The extents of modification (at each site) are approximately 25%, 50%, and approximately greater than 80% for I2/lysozyme molar ratios of 0.5, 1.0, and 2.5, respectively. At pH 4.5, the rates of reaction of both residues are about one-third or less of the rates at pH 5.5. When the reaction is carried out at pH 8.5 (with an I2/lysozyme molar ratio of 1.0), only the tyrosine residue is modified. Resonances observed in the spectra of the modified protein mixtures (but not in the spectrum of intact lysozyme) indicate that the modified Trp-108 residue is not oxindolealanine, but either delta1-hydroxytryptophan or an ester thereof. This result is consistent with previous evidence which indicates that the modified tryptophan is the Glu-35 ester of delta1-hydroxytryptophan-108 (Imoto, T., and Rupley, J.A. (1973) J. Mol. Biol. 80, 657-667; Beddell, C. R., Blake, C. C. F., and Oatley, S. J. (1975) J. Mol. Biol. 97, 643-654). The spectra also indicate that the modified tyrosine residue is predominantly monoiodinated. The spectra of modified protein samples subjected to denaturation with 6M guanidinium chloride for 24 h at 37 degrees (and the renatured) indicate that residue 108 is converted to about equal amounts of the two diastereoisomers of oxindolealanine. However, incubation in 6M guanidinium chloride for 2 h at 25 degrees does not cause measurable hydrolysis of the Glu-35 ester of delta1-hydroxytryptophan-108.
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PMID:Studies of chemical modifications of proteins by carbon 13 neuclear magnetic resonance spectroscopy. Reaction of hen egg white lysozyme with iodine. 98 24

We have previously shown that an antigenic site in native lysozyme resides around the disulphide bridge 30-115 and incorporates Lys-33 and Lys-116 and one or both of Tyr-20 and Tyr-23. These residues fall in an imaginary line circumscribing part of the surface of the molecule and passing through the spatially adjacent residues Tyr-20, Arg-21, Tyr-23, Lys-116, Asn-113, Arg-114, Phe-34 and Lys-33. The identity of the site was confirmed by demonstrating that the synthetic peptide Tyr-Arg-Tyr-Gly-Lys-Asn-Arg-Gly-Phe-Lys (which does not exist in lysozyme but simulates a surface region of it), and an analogue in which glycine replaced Tyr-23, possessed remarkable immuno-chemical reactivity that accounted entirely for the expected reactivity of the site in native lysozyme. Tyr-23 is not part of the site, and its contribution was satisfied by a glycine spacer. The novel approach presents a powerful technique for the delineation of antigenic (and other binding) sites in native proteins and confirms that these need not always comprise residues in direct peptide linkage.
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PMID:Delineation of the third antigenic site of lysozyme by application of a novel 'surface-simulation' synthetic approach directly linking the conformationally adjacent residues forming the site. 99 47

The photoionization of aromatic residues constitutes a major initial photochemical reaction in the flash photolysis of proteins at gamma greater than 250 nm. The ejected electrons have been observed as eaq- and the disulphide bridge electron adduct, and also must be trapped at unidentified sites. The number of tryptophyl (or tyrosyl) residues photo-ionized at 5 musec delay is approximately equal to the number of exposed residues. The flash photolysis data have been related to inactivation by considering how photolysis of these "photolabile" residues can affect enzymic activity, based on the microstructure and available information about permanent alterations and residue specificities. This analysis indicates that hen lysozyme and papain are inactivated by photolysis of an essential Trp residue, that bovine trypsin is inactivated by photolysis of a Trp residue adjacent to the key catalytic Ser and other pathways initiated by excitation of Tyr and Cys, that the efficient photoionization of Tyr and RNase A is not an important inactivating reaction, and that aromatic residues in subtilisn Carlsberg are photosensitive.
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PMID:Flash photolysis of enzymes. 108 37

The ability of aromatic tryptophyl and tyrosyl side-chain donors to form charge-transfer (CT) complexes with the acceptor 1-methyl-3-carbamidopyridinium chloride has been used to investigate the degree of exposure of these aromatic residues in denaturated proteins. The coplanar geometry of the CT complexes requires that virtually a full ring face of the donor be available for interaction with the acceptor, and the aromatic donor residues of lysozyme, trypsin, chymotrypsin, and the zymogens of the latter two enzymes do not appear to be wholly "exposed" in 6 M guanidine hydrochloride. Comparison of the CT proerties of the proteins with the corresponding properties of model complexes suggests that the incomplete exposure is due at least in part to statistical fluctuations in the continuously mobile, randomly coiled polypeptide chain which result in residues being alternately fully exposed and partly covered. Reduction and alkylation of the disulfide cross-links increase the apparent availability of the aromatic residues but the exposure is still less than that expected from a comparable mixture of tryptophan and tyrosine residues. Previous studies on the exposure of the aromatic residues of lysozyme and trypsin in aqueous salt solutions, when taken together with the present results, further suggest that there are two distinct kinds of surface environment possible on native proteins in solution. Some residues appear to be located in areas of the protein surface which are characterized by relatively fixed or stable local conformations, and have apparent CT association constants closely resembling these of comparable model complexes. Other residues may be located in a region where the protein conformation is flexible or continuously mobile, as evidenced by their smaller apparent association constants. It is probably significant that Trp-62 of lysozyme and Trp-215 of trypsin, both specificity site residues, appear to belong to the class of residues which can be considered as being in a flexible environment on the protein surface.
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PMID:Charge-transfer studies of the availability of aromatic side chains of proteins in guanidine hydrochloride. 117 11

1. Procedure for the isolation of peptides from proteins bearing the chemically labile aromatic ether, O-tyrosyl-4-nitrobenz-2-oxa-1,3-diazole group, is described. 2. The tyrosyl residue reactive towards 7-chloro-4-nitrobenz-2-oxa-1,3-diazole in chicken egg white lysozyme (Aboderin, A. A., Boedefeld, E. and Luisi, P. L., (1973) Biochim. Biophys. Acta 328. 20-30) is tyrosine-23. The amino group in the protein whose reaction with the reagent is dependent on the prior reaction of tyrosine-23 is the epsilon-amino group of lysine-33.
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PMID:Reaction of chicken egg white lysozyme with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole. II. Sites of modification. 124 79

The ability of the lectin concanavalin A (ConA) and N-formyl-methionyl-leucyl-phenylalanine (fMLF) to induce protein-tyrosine phosphorylation in human neutrophils was examined by immunoblot analysis. ConA caused an increase in tyrosine phosphorylation of protein bands with apparent molecular masses of 120, 80, 76, 66 and 40 kDa; on the other hand, fMLF caused an increase in those of only 80-kDa and 40-kDa proteins. These protein-tyrosine phosphorylations were time- and dose-dependent. The tyrosine phosphorylation of 40-kDa protein induced by fMLF was suppressed but that by ConA was not suppressed by pertussis toxin pretreatment. At the same time, pertussis toxin pretreatment also inhibited lysozyme release and aggregation of neutrophils induced by fMLF but did not inhibit those responses induced by ConA. These results suggest that the tyrosine phosphorylation of 40-kDa protein may be involved in a part of neutrophil activation and be regulated via pleiotropic signal transduction pathways. In addition, immunoblot analysis employing antibodies against microtubule-associated protein 2 (MAP2) kinase suggested that this tyrosine-phosphorylated 40-kDa protein might be the MAP2 kinase.
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PMID:Protein-tyrosine phosphorylations induced by concanavalin A and N-formyl-methionyl-leucyl-phenylalanine in human neutrophils. 131 40


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