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)

Histones were obtained from young and old rat livers by extracting them in 0.25 N HCl. They were fractionated on 15% acid urea polyacrylamide gels containing 6.25 M urea and the changes in the ratio of the major histone fractions as a function of age were calculated. Data presented show a significant increase in the amount of H1 degree fraction in the liver of old rats as compared to young rats. This data is discussed and the possible involvement of H1 degree fraction in an increased resistance of old rat liver chromatin to micrococcal nuclease digestion of linker DNA is suggested. Finally, in connection with this increased resistance, some possible consequences in chromatin structure are discussed.
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PMID:Age changes in the H1 group of histones from rat liver. 714 Aug 57

Titration of a salt-free solution of native staphylococcal nuclease by HCl leads to an unfolding transition in the vicinity of pH 4, as determined by near- and far-UV circular dichroism. At pH 2-3, the protein is substantially unfolded. The addition of further HCl results in a second transition, this one to a more structured species (the A state) with the properties of an expanded molten globule, namely substantial secondary structure, little or no tertiary structure, relatively compact size as determined by hydrodynamic radius, and the ability to bind the hydrophobic dye 1-anilino-8-naphthalene sulfonic acid. The addition of anions, in the form of neutral salts, to the acid-unfolded state at pH 2 also causes a transition leading to the A state. Fourier transform infrared analysis of the amide I band was used to compare the amount and type of secondary structure in the native and A states. A significant decrease in alpha-helix structure, with a corresponding increase in beta or extended structure, was observed in the A state, compared to the native state. A model to account for such compact denatured states is proposed.
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PMID:Characterization of the stable, acid-induced, molten globule-like state of staphylococcal nuclease. 835 98

We developed a recombinant DNA system to overexpress a fusion protein between the small, minimally soluble acute phase serum protein, serum amyloid A (SAA), and the bacterial enzyme staphylococcal nuclease (SN). This fusion protein is very soluble and is immunoreactive to polyclonal anti-SAA antibodies. Tryptophan fluorescence shows smooth denaturation curves for the fusion protein in guanidinium HCl or potassium thiocyanate. Fluorescence also indicates that only a single tryptophan residue (of the four present) is accessible to iodide quenching and, presumably, is exposed on the surface of the fusion protein. Circular dichroism (CD) shows a significant signal indicating alpha-helix, which can be attributed to the SAA portion of the molecule; these are the first CD spectral data available for SAA. pH titration shows persistence of helix domains for the fusion protein at pH 3.0, in contrast to the denaturation of SN under the same conditions. (The entire fusion protein shows a random coil pattern below pH 3.0.) By exploiting the structural and solubility properties of SN, this fusion protein has provided the first structural data about SAA-the precursor of the amyloid deposits in secondary amyloidosis. This fusion protein should be useful for further physical and physiologic studies of SAA.
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PMID:A fusion protein between serum amyloid A and staphylococcal nuclease--synthesis, purification, and structural studies. 953 22

Conformational features of a truncated (14 amino acid residues deleted from the C-terminus) staphylococcal nuclease R (SNR135) and the ternary complex of SNR135-Ca2+-pdTp were studied using circular dichroism (CD) spectra and 1-anilinonaphthalene-8-sulfonate (ANS)-binding fluorescence spectra under different conditions. Kinetic parameters such as KDNAM, KDNAS, KCaM, KCaA, and KpdTpd of SNR135 were also determined. The results show that SNR135 contains some residual secondary structure and some tertiary structure elements as indicated by far-UV and near-UV CD spectra and that it has the ability to fold into a native-like state in the presence of pdTp and Ca2+, but there are obvious differences both in secondary structure and in tertiary structure between the SNR135-Ca2+-pdTp complex and SNase R. The unfolding curves in Gdn-HCl show that the stability of the native-like conformation of the SNR135-Ca2+-pdTp complex is much less than that of SNase R though the ligand (Ca2+, pdTp) binding increases the stability of the SNR135-Ca2+-pdTp complex to some extent. Comparison of the kinetic parameters of SNR135 with those of the full-length nuclease shows that both SNR135 and SNase R have the same value of KpdTpd and very similar values of KCaM and KCaA, but SNR135 has larger values of KDNAM and KDNAS than SNase R. Such results indicate that the C-terminal deletion for SNR135 does not greatly affect the ligand (Ca2+, pdTp) binding and decreases the binding affinity of the DNA substrate to the nuclease, implying that the amino acid residues at the ligand binding sites in SNR135 are probably arranged in a similar topology to those in SNase R and that effective binding of the DNA substrate to the enzyme needs the conformational integrity of the entire enzyme molecule. Furthermore, it is suggested that the binding sites of pdTp and DNA substrate may overlap but are not exactly the same. This paper also provides evidence obtained by monitoring ANS-binding fluorescence that the partially unfolded conformation of SNR135 is not in the molten globule state.
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PMID:Conformational features of a truncated staphylococcal nuclease R (SNR135) and their implications for catalysis. 982 26


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