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)

A highly specific aggregation factor for Streptococcus sanguis H1 (AFH1) was obtained by lysozyme treatment of Actinomyces viscosus T14V. At 1 micrograms/ml, AFH1 aggregated a suspension of S. sanguis H1, with which A. viscosus T14V coaggregates by a mechanism not inhibited by lactose: even at much higher levels AFH1 caused little or no aggregation of streptococci from other coaggregation groups (J. O. Cisar et al., Infect. Immun. 24:742-752, 1979). The most active fraction of AFH1 obtained by gel chromatography (near the void volume of Bio-Gel A1.5 m) reacted as a single antigen with anti-A. viscosus T14V serum and was unrelated to the fimbrial antigens of A. viscosus T14V. Smaller molecular fractions, at high levels, inhibited aggregation of S. sanguis H1 by high-molecular-weight AFH1 as well as coaggregation of S. sanguis H1 with A. viscosus T14V. The AFH1 fraction with high aggregating activity was composed of approximately 53% cell wall components (alanine, glutamine, lysine, N-acetylglucosamine, and N-acetylmuramic acid). 40% polysaccharide (N-acetylgalactosamine, rhamnose, and 6-deoxytalose), and 7% protein; teichoic acid was not detected. The fraction which inhibited aggregation and coaggregation contained much less of the cell wall constituents and more of the polysaccharide than the fraction with potent aggregating activity. Aggregation was completely prevented either by treating AFH1 with 0.01 M periodate at 25 degrees C for 4 h or by treating S. sanguis H1 with heat or pronase. A role for electrostatic forces in the aggregation was indicated by: (i) NaCl inhibition of aggregation, and (ii) a great decrease in aggregation potency as a result of chemical modification of either cationic or anionic groups of AFH1. On the other hand, NaCl reversed the aggregation only very weakly. The overall data suggest that a carbohydrate-protein interaction may be dominant in the aggregation of S. sanguis H1 by AFH1 and in the coaggregation of S. sanguis H1 with A. viscosus T14V.
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PMID:A factor from Actinomyces viscosus T14V that specifically aggregates Streptococcus sanguis H1. 630 57

Pyridine borane has been reported as a superior reagent over a wide pH range, 5-9, for the reductive methylation of amino groups of proteins with formaldehyde [J. C. Cabacungan , A. I. Ahmed , and R. E. Feeney (1982) Anal. Biochem. 124, 272-278]. It has also been reported to reduce tryptophan to dihydrotryptophan and to inactivate lysozyme in trifluoroacetic acid [M. Kurata , Y. Kikugawa , T. Kuwae , I. Koyama , and T. Takagi (1980) Chem. Pharm . Bull 28, 2274-2275]. In the present study the specificity of pyridine borane for the two different modifications under different reaction conditions has been demonstrated, and extended to the application to the synthesis of protein containing reductively attached carbohydrates. In the acid reduction, pyridine borane selectively reduced all six tryptophans in lysozyme to dihydrotryptophan while all other amino acids remained intact. On similar treatment no cleavage of the carbohydrate moiety from chicken ovomucoid, and no losses of activity of ovomucoid or ribonuclease, two proteins devoid of tryptophan, were observed. Nearly complete methylation of the lysines of lysozyme, chicken ovomucoid, and ribonuclease was achieved with formaldehyde at pH 7.0 after 2 h at room temperature, with the retention of full activity of the protein without any destruction of tryptophan. The same chemistry was applied to covalently attach glucose and lactose to bovine serum albumin. Parameters, including pH, temperature, and methanol, that affect the reactions were investigated. Incremental additions of pyridine borane during the course of the reactions increased the rate of modification. The covalent attachment of sugar to the epsilon-amino group of lysine was demonstrated by the synthesis of N-alpha- acetylglucitollysine and comparison with acid hydrolysates of the bovine serum albumin-sugar derivatives.
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PMID:Pyridine borane as a reducing agent for proteins. 643 Jan 22

alpha-Lactalbumin (alpha-LA) is a milk protein that interacts with the enzyme galactosyltransferase, modifying its substrate specificity in a way which promotes the transfer of galactose to glucose, resulting in a way which promotes the transfer of galactose to glucose, resulting in a beta-1----4 glycosidic linkage and the synthesis of lactose. Lysozyme, an enzyme which catalyses the hydrolysis of a beta-1----4 glycosidic linkage in polysaccharides, has been shown to be structurally related to alpha-LA and it has been proposed that they have arisen from a common ancestral gene. To compare their evolutionary relationships, we report here the complete nucleotide sequence of the rat alpha-LA gene, including its 5'-flanking sequences, and compare its gene structure with the chicken egg-white lysozyme gene. Both genes contain three introns at similar positions. The first three exons of the two genes have similar nucleotide sequences. The fourth exon of alpha-LA, which partly codes for the C-terminal residues of the protein, essential for its interaction with galactosyltransferase, is markedly different from the corresponding exon of the lysozyme gene and is preceded by two (TG)n repeats.
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PMID:Similarity of the nucleotide sequences of rat alpha-lactalbumin and chicken lysozyme genes. 670 45

alpha-Lactalbumin is an abundant milk-specific calcium metalloprotein which has an evolutionary relationship to lysozyme. It modifies the substrate specificity of a Golgi galactosyltransferase by forming the lactose synthetase binary complex. Lactose, together with other sugars and diffusible ions, is responsible for the osmotic pressure of milk. To assess the involvement of alpha-lactalbumin in lactogenesis, alpha-lactalbumin-deficient mice were created by disrupting the gene by homologous recombination in embryonic stem cells. Homozygous mutant mice are viable and fertile but females cannot feed their offspring. They produce a highly viscous milk that pups appear to be unable to remove from the mammary gland. This milk is rich in fat and protein and is devoid of alpha-lactalbumin and lactose. The phenotype of heterozygous mice was found to be intermediate, with a 40% decrease in alpha-lactalbumin but only a 10-20% decrease in the lactose content of their milk compared with wild-type animals. These results emphasize the key function of alpha-lactalbumin in lactogenesis and open new opportunities to manipulate milk composition.
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PMID:Creation and phenotypic analysis of alpha-lactalbumin-deficient mice. 802 17

The in vitro lysozyme susceptibility of three oral isolates of Candida albicans cultured in carbohydrate-supplemented media was studied. Lysozyme was shown to have a dose- and time-dependent killing effect on C. albicans isolates. Fungicidal activity persisted to varying degrees when yeast isolates were cultured in a variety of carbohydrates (glucose, galactose, sucrose, maltose, xylitol and lactose) before exposure to 20 micrograms/ml lysozyme. Sucrose and galactose grown yeasts exhibited increased resistance to lysozyme compared with (in decreasing order) those grown in glucose, maltose, xylitol or lactose. Further, the C. albicans isolates tested demonstrated strain variations in their susceptibility to lysozyme. These results suggest that dietary carbohydrate may play a role in modulating the yeast cell populations in the oral cavity by altering the fungal susceptibility to salivary lysozyme.
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PMID:The in vitro lysozyme susceptibility of Candida albicans cultured in carbohydrate-supplemented media. 823 72

Carbohydrates are T cell independent antigens because they do not bind to MHC molecules. However, glycopeptides might potentially bind to MHC molecules via their peptide component for presentation to T cells. We have conjugated the disaccharide galabiose [Gal alpha (1-4)Gal beta] to the amino terminus of a T cell peptide determinant from hen egg-white lysozyme [HEL(52-61)]. The resulting glycopeptide (Gal2-52-61) and a nonglycosylated analogue containing tyrosine and glutamic acid at the amino-terminus (YE-52-61) bound equally well to purified I-Ak. T cell hybridomas were produced after immunization with Gal2-52-61. Many of the T cell hybridomas were glycopeptide-specific and responded to Gal2-52-61 but not to nonglycosylated synthetic peptides or to HEL presented by APC, indicating that the carbohydrate moiety influenced T cell recognition. Recognition was lost with the amino terminal attachment of the disaccharide to a peptide six amino acids longer at the amino terminus than HEL(52-61). Recognition also was lost with peptides containing only a single galactosyl residue or with galabiose bound to a different I-Ak binding peptide. T cells directed to Gal2-52-61 recognized glycopeptides having significant variation in the disaccharide structure, such as HEL(52-61) glycopeptides carrying lactose, cellobiose, or hepta-o-acetylated galabiose. Peptide residues were important features of the T cell epitope; Ala substitutions of two critical T cell contact residues of HEL(52-61) (Tyr53 and Leu56) abrogated T cell reactivity to the glycopeptides without affecting binding to I-Ak. In conclusion, we propose that these T cells recognize a peptide conformation specific to glycopeptide-I-Ak complexes and that this recognition does not involve specific interaction between the carbohydrate moiety and the T cell receptor.
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PMID:Glycopeptides bind MHC molecules and elicit specific T cell responses. 836 Apr 71

alpha-Lactalbumin was isolated from the whey fraction of platypus (Ornithorhynchus anatinus) milk by successive ion-exchange, hydrophobic interaction and gel-permeation chromatography. The purified protein modified the action of partially-purified galactosyltransferase from platypus milk to promote the synthesis of lactose, but had very little modifier effect on bovine galactosyltransferase. Platypus alpha-lactalbumin has 126 amino-acid residues (molecular mass about 14.3 kDa), including a three-residue insertion not found in other alpha-lactalbumins or c-type lysozymes. It appears to have two sites of post-translational modification, of which at least one is N-glycosylated, to give an apparent molecular mass of 23 kDa on SDS-PAGE. The platypus sequence shows a high degree of positional identity (41-48%) with the alpha-lactalbumins of other species. Although it has no lysozyme activity, platypus alpha-lactalbumin is more similar to mammalian lysozymes than is any eutherian or marsupial alpha-lactalbumin, suggesting that this monotreme protein has evolved more slowly than other alpha-lactalbumins.
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PMID:Isolation, partial characterisation, and amino acid sequence of alpha-lactalbumin from platypus (Ornithorhynchus anatinus) milk. 843 67

High-performance liquid chromatography has been applied to determination of modifier activity in alpha-lactalbumin (alpha-LA). An amino-bonded column separates uridine diphosphate (UDP) (product), UDPgalactose (substrate), and uridine monophosphate (UMP). From an aliquot of the same sample, a column for carbohydrate analysis separates lactose (the other product) and galactose-1,2-cyclic phosphate (Gal-c-P). Nucleotide peaks are detected by measurement of A262 and those of carbohydrate by 3H counting, the isotope originating from UDP-galactose-3H. A pH of 6.3 was taken as optimal for production of UDP since, at this level, the unwanted side reaction is minimized, by which UMP and Gal-c-P are formed. Thus, the conservation of substrate so effected may have contributed to an enhanced production of UDP. The reaction by which UDP and lactose are produced was linear for 120 min, as followed by UDP formation, but it continued to at least 300 min. Production of lactose was equivalent to that of UDP, when alpha-LA was the modifying protein. From a survey of seven other proteins, only lysozyme and ovalbumin showed ability to produce UDP. However, failure of the last two proteins to produce lactose indicates absence of modifier activity and demonstrates the need for monitoring both products.
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PMID:Application of high-performance liquid chromatography to determination of modifier activity in alpha-lactalbumin and other proteins. 857 96

The use of molecular genetics to introduce both a metal ion binding site and a nitroxide spin label into the same protein opens the use of paramagnetic metalnitroxyl interactions to estimate intramolecular distances in a wide variety of proteins. In this report, a His-Xaa3-His metal ion binding motif was introduced at the N terminus of the long interdomain helix of T4 lysozyme (Lys-65 --> His/Gln-69 --> His) of three mutants, each containing a single nitroxide-labeled cysteine residue at position 71, 76, or 80. The results show that Cu(II)-induced relaxation effects on the nitroxide can be quantitatively analyzed in terms of interspin distance in the range of 10-25 A using Redfield theory, as first suggested by Leigh [Leigh, J.S. (1970) J. Chem. Phys. 52, 2608-2612]. Of particular interest is the observation that distances can be determined both under rigid lattice conditions in frozen solution and in the presence of motion of the spins at room temperature under physiological conditions. The method should be particularly attractive for investigating structure in membrane proteins that are difficult to crystallize. In the accompanying paper, the technique is applied to a polytopic membrane protein, lactose permease.
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PMID:A method for distance determination in proteins using a designed metal ion binding site and site-directed spin labeling: evaluation with T4 lysozyme. 861 88

As shown in the accompanying paper, the magnetic dipolar interaction between site-directed metal-nitroxide pairs can be exploited to measure distances in T4 lysozyme, a protein of known structure. To evaluate this potentially powerful method for general use, particularly with membrane proteins that are difficult to crystallize, both a paramagnetic metal ion binding site and a nitroxide side chain were introduced at selected positions in the lactose permease of Escherichia coli, a paradigm for polytopic membrane proteins. Thus, three individual cysteine residues were introduced into putative helix IV of a lactose permease mutant devoid of native cysteine residues containing a high-affinity divalent metal ion binding site in the form of six contiguous histidine residues in the periplasmic loop between helices III and IV. In addition, the construct contained a biotin acceptor domain in the middle cytoplasmic loop to facilitate purification. After purification and spin labeling, electron paramagnetic resonance spectra were obtained with the purified proteins in the absence and presence of Cu(II). The results demonstrate that positions 103, 111, and 121 are 8, 14, and > 23 A from the metal binding site. These data are consistent with an alpha-helical conformation of transmembrane domain IV of the permease. Application of the technique to determine helix packing in lactose permease is discussed.
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PMID:Distance determination in proteins using designed metal ion binding sites and site-directed spin labeling: application to the lactose permease of Escherichia coli. 861 89


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