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)

Dynamic structures of globular proteins are studied on the basis of correlative movements of residues around their native conformations, which are computed by means of the normal mode analysis. To describe the dynamic structures of a protein, the core regions moving with strong positive or negative correlations to other regions of the polypeptide chain are detected from the correlation maps of the movements of residues. Such core regions are different, according to the definition, from the regions defined from a geometrical point of view, such as secondary structures, domains, modules, and so on. The core regions are actually detected for four proteins, myoglobin, Bence-Jones protein, flavodoxin, and hen egg-white lysozyme, with different folding types from each other. The results show that some of them coincide with the secondary structures, domains, or modules, but others do not. Then, the dynamic structure of each protein is discussed in terms of the dynamic cores detected, as compared with the secondary structures, domains, and modules.
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PMID:Dynamic structures of globular proteins with respect to correlative movements of residues calculated in the normal mode analysis. 261 Aug 55

The generally accepted hypothesis that exons code for fundamental polypeptide structures was tested with a fusion protein consisting of almost the entire polypeptide coded by exon 2 of chicken lysozyme fused to the N-terminus of beta-galactosidase of E.coli. Exon 2 encodes residues 28-81 of lysozyme. It thus contains Glu 35 and Asp 52, which are essential for hydrolysis of glycosidic bonds. The exon 2-beta-galactosidase fusion protein hydrolysed the substrate 4-methylumbelliferyl-N,N',N''-triacetyl-chitotrioside with a reaction rate about 1/40,000 of that of native lysozyme. The low hydrolysis rate of exon 2-peptide is partially caused by its low affinity to its substrate.
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PMID:50 residues coded by exon 2 of chicken lysozyme carry residual catalytic activity. 264 4

Current knowledge about the etiology and histogenesis of keratoacanthoma (KA) is first reviewed, after which the various clinical and histological patterns of this tumor are presented. The differential diagnosis, particularly against spinocellular carcinoma (SCC), and possible forms of therapy are discussed. A series of 90 KAs seen in the period 1976-1986 were investigated histopathologically with reference to the overall architecture, the epithelial differentiation, the behavior towards the adjacent tissue, and the extent and composition of the cellular infiltrate. In addition to routine staining with hematoxylin-eosin and Giemsa, several files have been subjected to immunohistological analysis by means of the peroxidase-antiperoxidase method (PAP) (keratin, lysozyme, epithelial membrane antigen, tissue polypeptide antigen). In 79 cases (88%) the overall architecture found was that of an endo-exophytic, dome-shaped structure with a central crater filled with a plug and with epithelial "lips" at the margins. In 3 KA (3%) a more endophytic picture was seen though no ulceration was observed. In 2 tumors in the very early stages (2%), there was no formation of horn crater and no epithelial lips. Similarly, 5 flat, plaque-like KA (6%) also showed no horn crater. With the exception of 3 aggregated (and/or multicentric) KA (3%), no solitary or multiple types were found. In 88 cases (98%), proliferation of the epidermis was observed mainly in the lateral and basal parts. In 86 KA (96%) there was a relatively well-demarcated, sharp border to the basal tumor portions. In 4 cases (4%) a less precise definition of the outer tumor margins was observed, because of a considerable pseudocarcinomatous, though not truly infiltrative, growth pattern. In 24 KA (27%) there was a strong tendency to formation of one or more sequesters. In the majority of cases, maturation of the epithelial cells was normal. Abnormal multipolar mitoses (7 cases; 8%) and relatively pronounced cellular atypies (8 cases; 9%) were occasionally observed. There was a clear correlation between the composition and extent of the inflammatory infiltrate and the tumor growth stage. In 78 KA (87%) large numbers of intraepithelial neutrophilic microabscesses were shown. In only 13 cases (14%) were substantial numbers of eosinophilic leukocytes observed, and 3 of these tumors (3%) later developed eosinophilic microabscesses.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Keratoacanthoma and its clinical variants. Review of the literature and histopathologic analysis of 90 cases]. 265 49

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.
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PMID:Stabilization of phage T4 lysozyme by engineered disulfide bonds. 267 95

Multiple replacements at amino acid position 3 of bacteriophage T4 lysozyme have shown that the conformational stability of the protein is directly governed by the hydrophobicity of the residue substituted (Matsumura, M., Becktel, W. J., and Matthews, B. W. (1988) Nature 334, 406-410). Of the 13 mutant lysozymes made by site-directed mutagenesis, two variants, one with valine (I3V) and the other with tyrosine (I3Y), were crystallized and their structures solved. In this report we describe the crystal structures of these variants at 1.7 A resolution. While the structure of the I3V mutant is essentially the same as that of wild-type lysozyme, the I3Y mutant has substantial changes in its structure. The most significant of these are that the side chain of the tyrosine is not accommodated within the interior of the protein and the amino-terminal polypeptide (residues 1-9) moves 0.6-1.1 A relative to the wild-type structure. Using coordinates based on the wild-type and available mutant structures, solvent accessible surface area of residue 3 as well as the adjacent 9 residues in the folded form were calculated. The free energy of stabilization based on the transfer of these residues from a fully extended form to the interior to the folded protein was found to correlate well with the protein stability determined by thermodynamic analysis. The enhanced thermostability of the variant Ile-3----Leu, relative to wild-type lysozyme, can also be rationalized by surface-area calculations based on a model-built structure. Noncrystallization of most lysozyme variants at position 3 appears to be due to disruption of intermolecular contacts in the crystal. The Ile-3----Val variant is closely isomorphous with wild-type and maintains the same crystal contacts. In the Ile-3----Tyr variant, however, a new set of contacts is made in which direct protein-protein hydrogen bonds are replaced by protein-water-protein hydrogen bonds as well as a novel hydrogen bond involving the phenolic hydroxyl of the substituted tyrosine.
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PMID:Structural studies of mutants of T4 lysozyme that alter hydrophobic stabilization. 267 24

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.
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PMID:Principles of protein architecture. 269 41

When recombinant ricin A chain transcripts are translated in a rabbit reticulocyte lysate the ribosomes are rapidly inactivated as shown by their inability to support translation of yeast preproalpha factor or chicken lysozyme transcripts added subsequently. In contrast, ribosomes which have translated transcripts encoding non-toxic polypeptides such as ricin B chain, readily translate the second transcript under identical conditions. Ribosome inactivation is accompanied by a highly specific modification of 28S rRNA which occurs at the same position as the N-glycosidic cleavage of an adenine residue and which is thought to cause inactivation of the ribosomes. Protein synthesis by wheat germ ribosomes was not inhibited under the conditions which inhibit reticulocyte ribosomes confirming earlier observations that plant cytoplasmic ribosomes are much less sensitive to inhibition by ricin A chain than are mammalian ribosomes. Using the same assay we have shown that deleting an internal hexapeptide, which shares homology with hamster elongation factor-2, completely abolishes catalytic activity. Deleting a second pentapeptide conserved between ricin A chain and the ribosome-inactivating plant toxin trichosanthin, had no effect. Deleting the first nine residues from the N-terminus of A chain did not affect toxicity whereas deleting a further three residues inactivated the polypeptide. Point mutations which individually converted arginine 48 and arginine 56 of ricin A chain to alanine residues or which deleted arginine 56 were also without effect on the catalytic activity of the toxin.
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PMID:Ribosome inactivation by ricin A chain: a sensitive method to assess the activity of wild-type and mutant polypeptides. 271 55

Disulphide bonds can significantly stabilize the native structures of proteins. The effect is presumed to be due mainly to a decrease in the configurational chain entropy of the unfolded polypeptide. In phage T4 lysozyme, a disulphide-free enzyme, engineered disulphide mutants that crosslink residues 3-97, 9-164 and 21-142 are significantly more stable than the wild-type protein. To investigate the effect of multiple-disulphide bonds on protein stability, mutants were constructed in which two or three stabilizing disulphide bridges were combined in the same protein. Reversible thermal denaturation shows that the increase in melting temperature resulting from the individual disulphide bonds is approximately additive. The triple-disulphide variant unfolds at a temperature 23.4 degrees C higher than wild-type lysozyme. The results demonstrate that a combination of disulphide bonds, each of which contributes to stability, can achieve substantial overall improvement in the stability of a protein.
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PMID:Substantial increase of protein stability by multiple disulphide bonds. 281 28

A post-translational protein modification system involving the polypeptide ubiquitin results in ubiquitin-protein conjugates of various functions. A ubiquitin-conjugating enzyme system was isolated from the epithelial tissue of bovine eye lens by DEAE-Sepharose and Bio-Gel A-1.5m column chromatography. The lens system shows similar enzymatic properties to the one from rabbit reticulocytes: requirement for ATP and sensitivity to thiol reagents. Two sets of prominent ubiquitin conjugates were formed with endogenous ubiquitin-acceptor proteins from fractions of the Bio-Gel column: a pair of ubiquitin conjugates of approximately 130 kDa and others with very high molecular mass. Extreme specificity is indicated by the ability of the lens system to catalyze conjugation of ubiquitin to the few endogenous acceptor proteins, or to histone H2B, but not to lysozyme, S-carboxymethylated bovine serum albumin, or native or heat-denatured lens alpha crystallin.
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PMID:Properties of the ubiquitin conjugation system from bovine eye lens. 284 35

Nine granular cell tumours were investigated with poly- or monoclonal antisera to neurone specific enolase (NSE), glial enolase (GE), S 100 protein, alpha-1-antichymotrypsin, lysozyme, laminin, neurofilament (NF), glial fibrillary acidic protein (GFAP), brain creatine kinase (CK), different cytokeratins (Keratin Dako, PKK1), tissue polypeptide antigen (TPA), carcinoembryonic antigen (CEA), desmin, myoglobin and leukocyte common antigen (LCA), using immunoperoxidase-methods on formalin fixed paraffin embedded sections. While five tumours from adults show specific cytoplasmic staining for NSE and S 100, three congenital tumours, two from the gingiva and one from palatine, show only a weak reaction for NSE, reflecting a possible origin from mature and immature Schwann cells, respectively. However, one subcutaneous tumour from near the clavicule of a ten year old girl differs from the other eight tumours by its specific cytoplasmic staining for alpha-1-antichymotrypsin only, supporting the view that there are granular cell tumours of histiocytic origin. In addition, the five adult NSE-S100 tumours show strong laminin-immunostaining around the single small or syncytial granular cells, whereas pericellular laminin is not detectable in the histiocytic nor in the three congenital tumours. None of the tumours shows any staining for lysozyme, epithelial, muscular, leukocyte, neurofilament or glial antigens.
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PMID:Immunohistochemical study of granular cell tumours. Demonstration of neurone specific enolase, S 100 protein, laminin and alpha-1-antichymotrypsin. 300 14


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