Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.31.1 (micrococcal nuclease)
 2,818 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chromatin and nucleosomal core particles were modified with cis-diamminedichloroplatinum (II) and the nucleoprotein complexes then digested with DNase I. Limited digestion of the modified chromatin containing cis-Pt(NH3)2Cl2 mediated cross-links involving the non-histone chromosomal proteins (Scovell et al. (1987) Biochem. Biophys. Res. Commun. 142, 826-835) does not release the low mobility proteins and excises only about 20% of the high mobility proteins 1, 2, and E. This supports previous findings that the low mobility proteins are involved primarily in protein-protein cross-links. In addition, the covalent cross-links between DNA and the high mobility proteins 1, 2, and E are relatively inaccessible to DNase I, in marked contrast to their accessibility to micrococcal nuclease. Furthermore, gels of the denatured DNA fragments obtained from digestion of both modified chromatin and nucleosomal core particle reveal virtually no difference in the 10n base repeat pattern, indicating no detectable change in the DNA-protein interactions upon DNA modification. This suggests that the predominant modification produced on core particle DNA, whether contained within higher order chromatin structure or in the core particle itself, is one which does not significantly alter the helical twist of the DNA within these nucleoprotein assemblies.
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PMID:cis-Diamminedichloroplatinum (II) modified chromatin and nucleosomal core particle probed with DNase I. 201 4

Alternating d(A-T)n sequences which are contiguous with DNA of effectively random sequence have an abnormal conformation in linear DNA molecules. These regions are strongly reactive towards chemical modification by osmium tetroxide, and are preferentially cleaved by micrococcal nuclease. Both the chemical modification and the enzymic cutting occur uniformly through the alternating tract, and there is no evidence for enzyme or chemical sensitivity in the interfaces between the tract and DNA of normal conformation. These reactivities have a requirement for an alternating sequence. In addition to chemical reactivity, alternating (A-T)n sequences exhibit anomalously small twist changes on cruciform formation, suggesting that the pre-extruded DNA is underwound. We propose that the alternating sequences adopt an altered conformation which is subject to easy torsional deformation.
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PMID:(A-T)n tracts embedded in random sequence DNA--formation of a structure which is chemically reactive and torsionally deformable. 379 41

Two classes of beta-sheet to beta-sheet packing can be distinguished in globular proteins. Both classes have beta sheets with the usual right-handed twist packed face to face. In orthogonal beta-sheet packings, the strand directions of the different beta sheets are 90 degrees to each other. Twisted beta sheets in this orientation have anticomplementary surfaces: one pair of diagonally opposite corners in the beta sheets is very close, and the other pairs of corners splay apart. At the close corners, the beta sheets are usually covalently connected: a strand that is part of one beta sheet turns through a right-handed bend to become part of the second beta sheet. The bend may occur at a beta bulge, or over a stretch of residues with a characteristic conformation, forming what we call a beta bend. Contacts between the beta sheets occur along the diagonal joining the close corners. They improve about one-fourth of the beta-sheet residues, and two-thirds of them are Val, Ile, or Leu. Elsewhere, the space between the beta sheets is filled by side chains from other parts of the protein, often alpha helices placed at the splayed corners. Examples of orthogonal beta-sheet packing are found in alcohol dehydrogenase, the acid proteases, the trypsin family, papain, staphylococcal nuclease, and thermolysin. In aligned beta-sheet packings, the angle between the strand directions of the packed beta sheets is approximately -30 degrees. In this orientation, the twisted beta-sheet surfaces are complementary. The principles governing this class of beta-sheet packings have been described previously. Here we discuss the difference and similarities of the aligned and orthogonal packing classes.
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PMID:Orthogonal packing of beta-pleated sheets in proteins. 675 82