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)

Membrane vesicles of Escherichia coli prepared by osmotic lysis of lysozyme ethylenediaminetetracetate (EDTA) spheroplasts have approximately 60% of the total membrane-bound reduced nicotinamide adenine dinucleotide (NADH) dehydrogenase (ED 1.6.99.3) and Mg2+-adenosine triphosphatase (ATPase) (EC 3.6.1.3) activities exposed on the outer surface of the inner membrane. Absorption of these vesicles with antiserum prepared against the purified soluble Mg2+-ATPase resulted in agglutination of approximately 95% of the inner membrane vesicles, as determined by dehydrogenase activity, and about 50% of the total membrane protein. The unagglutinated vesicles lacked all dehydrogenase activity and may consist of outer membrane. Lysozyme-EDTA vesicles actively transported calcium ion, using either NADH or adenosine 5'-triphosphate (ATP) as energy source. However, neither D-lactate nor reduced phenazine methosulfate energized calcium uptake, suggesting that the observed calcium uptake was not due to a small population of everted vesicles. Transport of calcium driven by either NADH or ATP was inhibited by simultaneous addition of D-lactate or reduced phenazine methosulfate. Proline transport driven by D-lactate oxidation was inhibited by either NADH oxidation or ATP hydrolysis. These results suggest that the portion of the total population of vesicles capable of active transport, i.e., the inner membrane vesicles, are functionally a homogeneous population but cannot be categorized as either right-side-out or everted, since activities normally associated with only one side of the inner membrane can be found on both sides of the membrane of these vesicles. Moreover, the data indicate that oxidation of NADH or hydrolysis of ATP by externally localized NADH dehydrogenase or Mg2+-ATPase establishes a protonmotive force of the opposite polarity from that established through D-lactate oxidation.
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PMID:Functional mosaicism of membrane proteins in vesicles of Escherichia coli. 19 Feb 12

Incubation of whole envelopes prepared from sonically oscillated Escherichia coli K-12 cultures with lysozyme in vitro resulted in the appearance of a protein species with an apparent molecular weight double that of outer membrane protein I. Similar dimers were also detected in purified outer membranes and whole envelopes from lysozyme-induced spheroplasts of E. coli K-12. This was confirmed by two-dimensional electrophoresis in which the dimers were resolved in the second dimension to run as single polypeptides of protein I. Formation of dimers was correlated with peptidoglycan degradation, but the ability of protein I molecules to associate may vary between strains of E. coli, since dimers were found only in outer membranes from E. coli W7. We suggest that extensive degradation of peptidoglycan leads to nonspecific formation of protein I aggregates, but that these aggregates do not occur in vivo.
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PMID:Lysozyme-promoted association of protein I molecules in the outer membrane of Escherichia coli. 33 40

A technique has been elaborated for preparation of deuterated membranes from deuterated cells of Micrococcus lysodeikticus containing 85--90% of deuterium according to the data of IR and PMR spectroscopy. Normal lysis of the deuterated cells of M. lysodeikticus requires a concentration of lysozyme which is eight times higher than for usual cells (8 mg per 1 g of wet deuterated cells) and an addition of the lytic enzymes E-2 (2 mg per 1 g of wet deuterated cells). Preparations of deuterated membranes purified from ribosomes and proteins can be obtained by treating of the lysate with RNAase and washing in 0.5 M NaCl. The purity of the deuterated membranes was evaluated by the evidence of electron microscopy, IR spectra and enzyme activities. After hydrogen atoms were substituted by deuterium, the secondary structure of the total membrane protein, the ratio between the activities of the respiratory chain enzymes, and the relative content of the lipid and protein components of the deuterated membranes remain at the same level as in the protonated ones.
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PMID:[Deuterated membranes of Micrococcus lysodeikticus: production and several biochemical properties]. 74 57

The cell envelope of Neisseria gonorrhoeae, colony type 4, was studied. Outer membrane was isolated by lysozyme and ethylenediaminetetraacetic acid treatment of plasmolyzed cells according to Wolf-Watz et al. (1973). The degree of purity of the membrane preparations was checked by electron microscopy. The membrane fraction obtained had a density of 1.25 g/cm(3), was rich in phospholipase A and lysophospholipase, and contained only 10% of the total membrane activity of succinate dehydrogenase and d-lactate dehydrogenase. The outer membrane protein profile after sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed at least six major proteins. The predominating protein showed a molecular weight of 35,000. The lipopolysaccharide component was characterized by gas chromatography. The carbohydrates found were galactose, glucose, and glucosamine. d-Glycero-l-manno-heptose was present in very low amounts. Lipid A contained lauric acid, stearic acid, and beta-hydroxy-myristic acid. About 20% of the fatty acids in the outer membrane was derived from lipid A. The phospholipids were characterized as phosphatidylethanolamine, phosphatidylglycerol, and diphosphatidylglycerol. There was no evidence for a lipoprotein anchored to the peptidoglycan. The peptidoglycan of N. gonorrhoeae was of the chemotype I. The cell envelope of N. gonorrhoeae was found to be highly permeable to gentian violet. Cell envelopes of one penicillin-resistant and two penicillin-sensitive strains were compared. Only moderate differences in fatty acid composition were found.
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PMID:Cell envelope of Neisseria gonorrhoeae: outer membrane and peptidoglycan composition of penicillin-sensitive and-resistant strains. 80 26

For identification of cysteine residues on microsequence analysis it is crucial to derivatize the sulfhydryl groups. This reaction requires a desalting step which often represents a major obstacle, especially if the sample consists of limited amounts of a hydrophobic membrane protein. An alkylation procedure is described, allowing efficient derivatization (greater than 90%) of cysteines and cystines even in low microgram quantities, as revealed by test analyses with lysozyme and a hydrophobic membrane protein. The modified protein is recovered in high yields in a form suitable for both microsequence analysis and amino acid analysis. The method involves electrophoretic desalting by miniaturized Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis and in situ alkylation after electro-transfer onto polyvinylidene difluoride membranes. Precautions against NH2-terminal blocking during sample preparations are provided. The general applicability of the method is illustrated by the structural characterization of the low abundance membrane receptor for human urokinase plasminogen activator.
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PMID:In situ alkylation of cysteine residues in a hydrophobic membrane protein immobilized on polyvinylidene difluoride membranes by electroblotting prior to microsequence and amino acid analysis. 131 93

The poliovirus 3AB gene has been cloned and overproduced in T7 expression vectors using different approaches to allow reduction of basal levels of expression. Expression of the poliovirus 3AB gene is highly toxic for E. coli cells, due to drastic changes induced in membrane permeability of the bacteria that lead to cell lysis when the T7 lysozyme is present. The best production of 3AB was achieved with the T7/lac system in cells lacking T7 lysozyme, where this toxic protein was synthesized to high levels and during several hours in the absence of cell lysis. These results show the efficient synthesis of a highly damaging membrane protein and open the possibility to apply heterologous gene expression in E. coli to other lytic proteins.
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PMID:Inducible expression of a toxic poliovirus membrane protein in Escherichia coli: comparative studies using different expression systems based on T7 promoters. 133 17

Lysis protein T of phage T4 is required to allow the phage's lysozyme to reach the murein layer of the cell envelope and cause lysis. Using fusions of the cloned gene t with that of the Escherichia coli alkaline phosphatase or a fragment of the gene for the outer membrane protein OmpA, it was possible to identify T as an integral protein of the plasma membrane. The protein was present in the membrane as a homooligomer and was active at very low cellular concentrations. Expression of the cloned gene t was lethal without causing gross leakiness of the membrane. The functional equivalent of T in phage lambda is protein S. An amber mutant of gene S can be complemented by gene t, although neither protein R of lambda (the functional equivalent of T4 lysozyme) nor S possess any sequence similarity with their T4 counterparts. The murein-degrading enzymes (including that of phage P22) have in common a relatively small size (molecular masses of ca. 18,000) and a rather basic nature not exhibited by other E. coli cystosolic proteins. The results suggest that T acts as a pore that is specific for this type of enzyme.
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PMID:Lysis protein T of bacteriophage T4. 146

Purification of a major placental membrane protein phosphotyrosine phosphatase (PTP-I) through the use of a nonhydrolysable phosphotyrosine analogue affinity ligand has enabled identification of the enzyme as a single polypeptide of at least 46 kDa. This phosphatase specifically dephosphorylates phosphotyrosine-containing substrates, including the src peptide, the epidermal-growth-factor receptor tyrosine kinase and the non-receptor tyrosine kinase p56lck. The p56lck can be dephosphorylated by PTP-I at two tyrosine residues (Tyr-394 and Tyr-505), which are differentially phosphorylated in vitro and in vivo and have been suggested to modulate kinase activity. The activity of PTP-I towards these substrates indicates a possible function of regulation of cellular tyrosine phosphorylation pathways at the level of growth-factor receptor and/or oncogene/proto-oncogene tyrosine kinases. Kinetic analyses show that PTP-I exhibits a Km value of about 2 microM with either src peptide or reduced, carboxyamidomethylated and maleylated (RCM)-lysozyme as substrate, and is inhibited in a mixed competitive manner by the polyanions heparin and poly(Glu4,Tyr1). Sequencing of PTP-I peptides reveals almost complete identity with sequences within the N-terminal half of the 37 kDa non-receptor tyrosine phosphatase 1B. However, the size and amino acid composition of PTP-I are similar to that of a higher-molecular-mass form of PTP 1B predicted from cDNA cloning. These results suggest that the 37 kDa PTP 1B is a proteolysed form of PTP-I, and provide evidence that a larger form of PTP 1B exists in vivo, at least in association with placental membranes.
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PMID:Purification and characterization of a higher-molecular-mass form of protein phosphotyrosine phosphatase (PTP 1B) from placental membranes. 164 96

The glycosyltransferase alpha-2,6-sialyltransferase (ST) is a Type II membrane protein localized to the Golgi apparatus. The first 44 amino acids of this protein were able to specify Golgi retention of a fused marker protein, lysozyme. This section of ST contains a transmembrane segment which serves as a non-cleaved signal anchor. When lysozyme was fused to an equivalent region of a cell surface protein it now appeared on the cell surface. Analysis of chimeras between the two proteins revealed that the transmembrane segment of ST specifies Golgi retention. Furthermore, altering this segment in full-length ST results in the protein accumulating on the cell surface. However, the retaining effect of the transmembrane domain of ST is augmented by the presence of adjacent lumenal and cytoplasmic sequences from ST. If these sequences are spaced apart by a transmembrane domain of the same length as that of ST they too can specify Golgi retention. Thus retention in the Golgi of ST appears to involve recognition of an extended region of the protein within and on both sides of the bilayer.
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PMID:Sequences within and adjacent to the transmembrane segment of alpha-2,6-sialyltransferase specify Golgi retention. 193 90

Important protein-based immunoreactivities have long been associated with the cell wall core of mycobacteria. In order to explore the molecular basis of such activities, purified cell walls of Mycobacterium tuberculosis were extracted with sodium dodecyl sulfate to produce an insoluble residue composed of the mycolylarabinogalactan-peptidoglycan complex and about 2% of unextractable protein. Treatment of the product from an avirulent strain of M. tuberculosis with trifluoromethanesulfonic acid released a single polypeptide with a molecular size of 23 kilodaltons, accounting for all of the insoluble cell wall protein. Extensive purification and then analysis of the 23-kilodalton protein demonstrated the absence of diaminopimelic acid, muramic acid, or other peptidoglycan components, pointing to either a novel linkage between protein and peptidoglycan or a noncovalent but tenacious association. The released 23-kilodalton protein showed amino acid homology and other similarities to the outer membrane protein OmpF of Escherichia coli. Although a similar product was released in small quantities from cell walls of the virulent M. tuberculosis Erdman and H37Rv by lysozyme treatment, the cell walls of virulent bacilli were dominated by the presence of poly-alpha-L-glutamine, accounting for as much as 10% of their weight. The poly-alpha-L-glutamine was successfully separated from the cell wall proper, demonstrating again the absence of a covalent association between peptidoglycan and the polymer. The antigenicity of these products is demonstrated, and their roles vis-a-vis analogous polypeptides from other bacteria in immunogenicity, pathogenicity, and bacterial physiology are discussed.
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PMID:Peptidoglycan-associated polypeptides of Mycobacterium tuberculosis. 210 89


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