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:3.1.31.1 (micrococcal nuclease)
2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interest in the inhibition of enzymes by their specific antibodies stems mainly from the fact that these systems can serve as suitable models in the study of neutralization of biologically active molecules in general. The interaction of enzymes with their specific antibodies generally leads to a reduction in their enzymatic activity. The mechanism of this inhibition is rarely a direct combination of the antibodies with the catalytic site, but is rather due to steric hindrance, namely, barring the access to the active site. In several systems the mechanism of the antibody effect is by conformational changes which it induces on the enzyme. In these cases, the interaction with the antibody may result either in inhibition or in enhancement of the enzymatic activity. In every instance, however, the effect of the antibody is dependent on its narrow specificity, namely, on the regions of the enzyme to which it is directed. The extent of inhibition or enhancement is, therefore, a reflection of the nature and distribution of the various antigenic determinants on the enzyme molecule. Antibodies specific exclusively to defined regions of an enzyme molecule can be prepared. This has been performed for both lysozyme and staphylococcal nuclease by two procedures: a) Selective separation of the relevant antibodies from the anti-enzyme serum by an immunoadsorbent containing a particular immunologically active fragment of the enzyme. b) The use of an isolated antigenic fragment of the enzyme, or a conjugate of it, for immunization. The antibodies thus prepared, specific toward a unique defined region of the lysozyme molecule (residues 60-83, denoted "loop") recognize the structural conformation of the fragment and are reactive with the intact enzyme molecule. Furthermore, a chemically synthesized loop-like derivative was proved immunologically identical with the natural fragment, and when forming a part of a completely synthetic conjugate, elicited conformation-specific antibodies, reactive with native lysozyme. These findings are relevant to the topic of an immunological approach to fertility control from two different viewpoints: In the first place they are informative regarding the specific inhibition by antibodies of sperm enzymes which partake in the fertilization process. Secondly, they encourage the synthetic approach for induction of an immune response toward hormones which are crucial in fertilization or implantation.
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PMID:Enzyme inhibition by antibodies. 4 83

We have utilized the gene 49(-) mutant-infected cells of bacteriophage T4D to accumulate large numbers of nucleic acid-protein intermediate head structures. These heads were used as substrates for experiments in the investigations of the mechanism of DNA packaging. Specifically, we have examined: (i) the susceptibility of the DNA in these structures to digestion by a variety of nucleases after a series of increasing temperature pulses from 25 to 100 degrees C, (ii) the physicochemical characteristics of the DNA inside these heads, and (iii) the mechanism by which proteins are displaced from the interior of the head after treatment with basic proteins. We isolated DNA from these gene 49(-) heads by use of gradient centrifugation procedures. The DNA had a molecular weight of 8 x 10(6) and a density of 1.697 +/- 0.005 g/cm(3), and it contained a short resistant fraction (SRF) which, when associated with the gene 49(-) heads, exhibited AT-protected regions that were not susceptible to micrococcal nuclease digestion. Such a fraction may contain pieces which are important in the initial association of the DNA with the prohead. Exposure of the gene 49(-) intermediate capsid structures to basic proteins, such as bovine trypsin inhibitor, lysozyme, and l-polylysine-70, caused a displacement of an amorphous-appearing structure which may be a complex of the gene 49(-) DNA and interior components of the capsid (e.g., internal proteins, polyamines). Our general conclusion is that in the gene 49(-) intermediate head structures which are only partly filled with DNA, this DNA is held inside the head by strong electrostatic linkages with interior polypeptides and polyamines.
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PMID:Bacteriophage T4D head morphogenesis. VIII. DNA-protein associations in intermediate head structures that accumulate in gene 49--mutant-infected cells. 87 37

Heat capacity, intrinsic viscosity and ellipticity of a number of globular proteins (pancreatic ribonuclease A, staphylococcal nuclease, hen egg-white lysozyme, myoglobin and cytochrome c) and a fibrillar protein (collagen) in various states (native, denatured, with and without disulfide crosslinks or a heme) have been studied experimentally over a broad range of temperatures. It is shown that the partial heat capacity of denatured protein significantly exceeds the heat capacity of native protein, especially in the case of globular proteins, and is close to the value calculated for an extended polypeptide chain from the known heat capacities of individual amino acid residues. The significant residual structure that appears at room temperature in the denatured states of some globular proteins (e.g. myoglobin and lysozyme) at neutral pH results in a slight decrease of the heat capacity, probably due to partial screening of the protein non-polar groups from water. The heat capacity of the unfolded state increases asymptotically, approaching a constant value at about 100 degrees C. The temperature dependence of the heat capacity of the native state, which can be determined over a much shorter range of temperature than that of the denatured state and, correspondingly, is less certain, appears to be linear up to 80 degrees C. Therefore, the denaturational heat capacity increment seems to be temperature-dependent and is likely to decrease to zero at about 140 degrees C.
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PMID:Heat capacity and conformation of proteins in the denatured state. 253 36

A variety of studies have documented multireactive antibodies in both the preimmune and naturally activated repertoire, but the relationship of these primarily IgM multireactive antibodies to antigen-specific primary and secondary response antibodies is currently not defined. In order to characterize the BALB/c preimmunization specificity repertoire and the baseline of naturally activated antibodies from which the immune response to a specific antigen (hen egg-white lysozyme, HEL) develops, panels of polyclonally activated blast-derived hybridomas (BlAbs) and natural antibody hybridomas (NAbs) from the spleens of unimmunized mice were screened for binding to a panel of nine complex antigens. Over half of the IgM-secreting BlAbs produced antibodies that were antigen-reactive; of these, over half were multireactive, i.e. capable of binding more than one complex antigen. There was no bias towards self vs foreign or thymus-dependent vs thymus-independent antigens. The frequency of antigen-reactive NAbs was about half the frequency of antigen-reactive antibodies found among the BlAbs. However, over half of the antigen-reactive NAbs were also multireactive, and the reactivity profile within the antigen-reactive subset of NAbs was similar to that within the antigen-reactive subset of BlAbs. These results suggest that the available repertoire of adult spleen cells contains a high proportion of multireactive antibodies, and that a subset of the available repertoire is randomly activated, yielding a small proportion of natural antibodies which closely reflect a random sampling of the available repertoire. Although monospecific precursor cells are rare, monospecific IgM BlAbs were found for all antigens in the panel except staphylococcal nuclease and mouse IgG. Monospecific as well as multireactive HEL-binding BlAbs were found at frequencies comparable to other protein antigens in the panel, and HEL-reactive NAbs were also present. On the other hand, it has previously been shown that HEL-reactive IgM antibodies (including multireactive antibodies whose specificities include HEL) are rare or absent in both the primary and secondary response to HEL. This cannot be attributed to an absence of available precursor B cells, and most likely reflects an early recruitment of HEL-reactive clones into the peripheral B cell pool. The possibility that polyreactive B cells may serve as precursors for some HEL-specific IgG antibodies is discussed.
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PMID:A substantial proportion of the adult BALB/c available B cell repertoire consists of multireactive B cells. 259 17

Small heat-stable, acid-soluble proteins (HASP) have been isolated from Bacillus subtilis nucleoids obtained from cell lysates of low ionic strength and lysozyme concentration. They were identified by their ability to bind homologous and heterologous native and denatured DNA. Four major species, of 8.5, 12, 23 and 26 kDal, were found. Their affinity for DNA was moderate as measured by the sensitivity to ionic strength of the DNA-protein complex (0.1-0.4 M-NaCl). Partial digestion by micrococcal nuclease of the 'low ionic strength nucleoids' released a DNA fragment of 80-120 bp. The data reported here indicate that small basic proteins, together with other components such as RNA, cations and polyamines, may be involved in the compaction of the prokaryotic genome.
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PMID:Isolation and characterization of small heat-stable acid-soluble DNA-binding proteins from Bacillus subtilis nucleoids. 392 47

The chromatin structure encompassing the lysozyme gene domain in hen oviduct nuclei was studied by measuring the partitioning of coding and flanking sequences during chromatin fractionation and by analyzing the nucleosome repeat in response to micrococcal nuclease digestion. Following micrococcal nuclease digestion, nuclei were sedimented to obtain a chromatin fraction released during digestion (S1) and then lysed in tris(hydroxymethyl)aminomethane-(ethylenedinitrilo)tetraacetic acid-[ethylenebis(oxyethylenenitrilo)]tetraacetic acid and centrifuged again to yield a second solubilized chromatin fraction (S2) and a pelleted fraction (P2). By dot-blot hybridization with 14 specific probes, it is found that the fractionation procedure defines three classes of sequences within the lysozyme gene domain. The coding sequences, which partition with fraction P2, are flanked by class I flanking sequences, which partition with fractions S1 and P2 and which extend over 11 kilobases (kb) on the 5'side and probably over about 4 kb on the 3' side. The partitioning of class II flanking sequences, which are located distal of class I flanking sequences, is different from that of class I flanking sequences. Coding sequences lack a canonical nucleosome repeat, class I flanking sequences possess a disturbed nucleosome repeat, and class II flanking sequences generate an extended nucleosomal ladder. Coding and class I flanking sequences are more readily digested by micrococcal nuclease than class II flanking sequences and the inactive beta A-globin gene. In hen liver, where the lysozyme gene is inactive, coding and class I flanking sequences fractionate into fractions S2 and P2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chromatin structure of the chicken lysozyme gene domain as determined by chromatin fractionation and micrococcal nuclease digestion. 395 10

A new procedure has been developed for the isolation of the chromosome complex, termed chromatin, from Escherichia coli. The bacteria were subjected to low ionic strength and T4 lysozyme, followed by detergent treatment analogous to that employed for the isolation of eukaryotic chromosomes. The chromatin was an insoluble viscous material which contained approximately equal amounts of DNA and RNA. The protein content of the chromatin was almost three times greater than the nucleic acid content. Electron microscopy revealed that the chromatin was highly condensed, having multiple loops and beaded structures with various diameters. The chromatin could be completely solubilized by both micrococcal nuclease and DNAase I, whereas RNAase had no effect. The initial degradation by micrococcal nuclease resulted in the production of a DNA-protein particle, sedimentation coefficient 10S, and an RNA-protein complex of 24S. Further degradation led to a decrease in sedimentation coefficient of the DNA-protein complex, but not of the RNA-protein particle. The peak size of the DNA of the initial DNA-protein particle was approximately 2400 bp. The action of micrococcal nuclease also resulted in the production of several discrete RNA species of various sizes. Several low molecular weight proteins (12000-27000) were found in the DNA-protein complex. The DNA-binding protein HU was present in the undigested chromatin; varying amounts of HU were, however, detected in the DNA-protein and RNA-protein particles.
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PMID:Isolation, properties and nucleolytic degradation of chromatin from Escherichia coli. 619 Sep 86

A total of 57 gram-positive, catalase-positive cocci, considered etiological agents of clinical and subclinical bovine mastitis, were tested for glucose and mannitol fermentation, coagulase and thermonuclease production, sensitivity to lysostaphin, gelatin hydrolysis, lysozyme, phosphatase and egg yolk factor production, hemolytic properties, antibiotic sensitivity, susceptibility to human and bovine phages, and enterotoxin production. All 57 strains were identified as staphylococci. A good correlation was found between 3+ and 4+ coagulase reactions, thermonuclease production, and high sensitivity to lysostaphin. Neither mannitol fermentation nor production of other enzymes appeared to be a specific property of bovine Staphylococcus aureus strains. beta- and delta-hemolysins were more frequently found than alpha-hemolysin. Nearly 40% of the strains were penicillin resistant. Strains were lysed by phage 42E from the human phage set more frequently than by phage 42D, whereas with the bovine set, strains were more sensitive to specific bovine phages. Three strains produced enterotoxin C, and one strain produced enterotoxin D.
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PMID:Characterization of staphylococci isolated from mastitic cows in Spain. 738 55

The stability changes caused by single amino acid substitutions are studied by a simple, empirical method which takes account of the free energy change in the compact denatured state as well as in the native state. The conformational free energy is estimated from effective inter-residue contact energies, as evaluated in our previous study. When this method is applied, with a simple assumption about the compactness of the denatured state, for single amino acid replacements at Glu49 of the tryptophan synthase alpha subunit and at Ile3 of bacteriophage T4 lysozyme, the estimates of the unfolding Gibbs free energy changes correlate well with observed values, especially for hydrophobic amino acids, and it also yields the same magnitudes of energy as the observed values for both proteins. When it is also applied for amino acid replacements at various positions to estimate the average number of contacts at each position in the denatured state from the observed value of unfolding free energy change, those values for replacements with Gly and Ala at the same residue position in staphylococcal nuclease correlate well with each other. The estimated numbers of contacts indicate that the protein is not fully expanded in the denatured state and also that the compact denatured state may have a substantially native-like topology, like the molten globule state, in that there is a weak correlation between the estimated average number of contacts at each residue position in the denatured state and the number of contacts in the native structure. These results provide some further evidence that the inter-residue contact energies as applied here (i) properly reflect actual inter-residue interactions and (ii) can be considered to be a pairwise hydrophobicity scale. Also, the results indicate that characterization of the denatured state is critical to understanding the folding process.
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PMID:Protein stability for single substitution mutants and the extent of local compactness in the denatured state. 785 36

6-O-[(2-Hydroxyethyl)poly(2-oxyethyl)]chitosan ("glycolchitosan") was oxidatively cleaved with nitrous acid and then partly acetylated with acetic anhydride, reacted with bromoacetyl-N-hydroxysuccinimide, and reacted further with acetic anhydride. Conditions were selected, including fractionation by size-exclusion chromatography, so that the resulting "Chitin Leash" had an estimated, average molecular weight of 10,000 (dextran standards), corresponding to a length of approximately 40 sugar residues. It possessed 0.9 terminal aldehyde and 2.6 random (presumably) side-chain bromoacetyl reactive groups per chain (average values). As a model system, the Chitin Leash was used to crosslink staphylococcal nuclease (SNase) to ribonuclease A (RNase) with retention of 75 and 78%, respectively, of the starting enzyme activities. For this coupling, the Nase was first converted to a sulfhydryl SNase derivative which retained 74% of the activity of starting enzyme. The yields in this synthesis were: 13% Chitin Leash from glycolchitosan, 24% Chitin Leash-RNase from Chitin Leash and 45% SNase-Chitin Leash-RNase from the latter conjugate. The ratio of SNase to RNase in this conjugate was 1.0:0.94. In a second preparation, in which [14C]acetic anhydride was used, a longer reaction time was employed for the coupling of Chitin Leash to RNase. This gave a 1.0:1.8:0.95 molar ratio of Nase: [14C]Chitin Leash: RNase, revealing multiple attachment of the [14C]Chitin Leash to RNase. The activity of the RNase in the final conjugate was 20%. The latter conjugate was approximately 70% hydrolyzed by diaminooctyl-succinyl-lysozyme, disconnecting the two enzymes while not affecting their activities.
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PMID:"Chitin Leash": a polysaccharide heterobifunctional cross-linking agent which can be cleaved by lysozyme. 837 39


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