Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nuclease A (NucA) is a nonspecific endonuclease from Anabaena sp. capable of degrading single- and double-stranded DNA and RNA in the presence of divalent metal ions. We have determined the structure of the delta(2-24),D121A mutant of NucA in the presence of Zn2+ and Mn2+ (PDB code 1ZM8). The mutations were introduced to remove the N-terminal signal peptide and to reduce the activity of the nonspecific nuclease, thereby reducing its toxicity to the Escherichia coli expression system. NucA contains a betabeta alpha metal finger motif and a hydrated Mn2+ ion at the active site. Unexpectedly, NucA was found to contain additional metal binding sites approximately 26 A apart from the catalytic metal binding site. A structural comparison between NucA and the closest analog for which structural data exist, the Serratia nuclease, indicates several interesting differences. First, NucA is a monomer rather than a dimer. Second, there is an unexpected structural homology between the N-terminal segments despite a poorly conserved sequence, which in Serratia includes a cysteine bridge thought to play a regulatory role. In addition, although a sequence alignment had suggested that NucA lacks a proposed catalytic residue corresponding to Arg57 in Serratia, the structure determined here indicates that Arg93 in NucA is positioned to fulfill this role. Based on comparison with DNA-bound nuclease structures of the betabeta alpha metal finger nuclease family and available mutational data on NucA, we propose that His124 acts as a catalytic base, and Arg93 participates in the catalysis possibly through stabilization of the transition state.
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PMID:Structural insights into the mechanism of nuclease A, a betabeta alpha metal nuclease from Anabaena. 1589 1

Restriction endonucleases and other nucleic acid cleaving enzymes form a large and extremely diverse superfamily that display little sequence similarity despite retaining a common core fold responsible for cleavage. The lack of significant sequence similarity between protein families makes homology inference a challenging task and hinders new family identification with traditional sequence-based approaches. Using the consensus fold recognition method Meta-BASIC that combines sequence profiles with predicted protein secondary structure, we identify nine new restriction endonuclease-like fold families among previously uncharacterized proteins and predict these proteins to cleave nucleic acid substrates. Application of transitive searches combined with gene neighborhood analysis allow us to confidently link these unknown families to a number of known restriction endonuclease-like structures and thus assign folds to the uncharacterized proteins. Finally, our method identifies a novel restriction endonuclease-like domain in the C-terminus of RecC that is not detected with structure-based searches of the existing PDB database.
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PMID:Identification of novel restriction endonuclease-like fold families among hypothetical proteins. 1597 56

Bacteriophage T4 RNase H, a flap endonuclease-1 family nuclease, removes RNA primers from lagging strand fragments. It has both 5' nuclease and flap endonuclease activities. Our previous structure of native T4 RNase H (PDB code 1TFR) revealed an active site composed of highly conserved Asp residues and two bound hydrated magnesium ions. Here, we report the crystal structure of T4 RNase H in complex with a fork DNA substrate bound in its active site. This is the first structure of a flap endonuclease-1 family protein with its complete branched substrate. The fork duplex interacts with an extended loop of the helix-hairpin-helix motif class 2. The 5' arm crosses over the active site, extending below the bridge (helical arch) region. Cleavage assays of this DNA substrate identify a primary cut site 7-bases in from the 5' arm. The scissile phosphate, the first bond in the duplex DNA adjacent to the 5' arm, lies above a magnesium binding site. The less ordered 3' arm reaches toward the C and N termini of the enzyme, which are binding sites for T4 32 protein and T4 45 clamp, respectively. In the crystal structure, the scissile bond is located within the double-stranded DNA, between the first two duplex nucleotides next to the 5' arm, and lies above a magnesium binding site. This complex provides important insight into substrate recognition and specificity of the flap endonuclease-1 enzymes.
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PMID:Crystal structure of bacteriophage T4 5' nuclease in complex with a branched DNA reveals how flap endonuclease-1 family nucleases bind their substrates. 1769 99

Nuclear magnetic resonance (NMR) spectroscopy provides a range of powerful techniques for determining the structures and the dynamics of proteins. The high-resolution determination of the structures of protein-protein complexes, however, is still a challenging problem for this approach, since it can normally provide only a limited amount of structural information at protein-protein interfaces. We present here the determination using NMR chemical shifts of the structure (PDB code 2K5X) of the cytotoxic endonuclease domain from bacterial toxin colicin (E9) in complex with its cognate immunity protein (Im9). In order to achieve this result, we introduce the CamDock method, which combines a flexible docking procedure with a refinement that exploits the structural information provided by chemical shifts. The results that we report thus indicate that chemical shifts can be used as structural restraints for the determination of the conformations of protein complexes that are difficult to obtain by more standard NMR approaches.
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PMID:Structure determination of protein-protein complexes using NMR chemical shifts: case of an endonuclease colicin-immunity protein complex. 1898 Mar 19

We demonstrate that the nucleocapsid protein of Sin Nombre hantavirus (SNV-N) has a DNA-specific endonuclease activity. Upon incubation of SNV-N with DNA in the presence of magnesium or manganese, we observed DNA digestion in sequence-unspecific manner. In contrast, RNA was not affected under the same conditions. Moreover, pre-treatment of SNV-N with RNase before DNA cleavage increased the endonucleolytic activity. Structure-based protein fold prediction using known structures from the PDB database revealed that Asp residues in positions 88 and 103 of SNV-N show sequence similarity with the active site of the restriction endonuclease HindIII. Crystal structure of HindIII predicts that residues Asp93 and Asp108 are essential for coordination of the metal ions required for HindIII DNA cleavage. Therefore, we hypothesized that homologous residues in SNV-N, Asp88 and Asp103, may have a similar function. Replacing Asp88 and Asp103 by alanine led to an SNV-N protein almost completely abrogated for endonuclease activity.
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PMID:Sin Nombre hantavirus nucleocapsid protein exhibits a metal-dependent DNA-specific endonucleolytic activity. 2726 91

Anticancer effects of L-ascorbic acid (Vitamin C, L-AA) have been reported in various types of cancers. L-AA intake reduces breast cancer recurrence and mortality; however, the role of L-AA in the treatment of breast cancer remains poorly understood. In this study, we investigated the effect and mechanism action of L-AA on breast cancer growth. L-AA inhibited the growth of breast cancer cells by inducing apoptotic cell death at the evaluated treatment concentrations without affecting normal cells. Moreover, L-AA induces autophagosome formation via regulation of mammalian target of rapamycin (mTOR), Beclin1, and autophagy-related genes (ATGs) and increased autophagic flux. Notably, we observed that L-AA increased p62/SQSTM1 (sequestosome 1) protein levels. Accumulation of p62 protein in cancer cells in response to stress has been reported, but its role in cancer regulation remains controversial. Here, we demonstrated that L-AA-induced p62 accumulation is related to L-AA-induced breast cancer growth inhibition. Furthermore, L-AA induced endoplasmic reticulum (ER) stress via the IRE-JNK-CHOP (inositol-requiring endonuclease-c-Jun N-terminal kinase-C/EBP homologous protein) signaling pathways, which increased the nuclear levels of p62/SQSTM1. These findings provide evidence that L-AA-induced ER stress could be crucial for p62 accumulation-dependent cell death, and L-AA can be useful in breast cancer treatment.
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PMID:L-Ascorbic Acid Inhibits Breast Cancer Growth by Inducing IRE/JNK/CHOP-Related Endoplasmic Reticulum Stress-Mediated p62/SQSTM1 Accumulation in the Nucleus. 3239 6

4-Substituted 2,4-dioxobutanoic acids inhibit influenza virus cap-dependent endonuclease (CEN) activity. Baloxavir marboxil, 4, is approved for treating influenza virus infections. We describe here the synthesis and biological evaluation of active compounds, 5a-5g, and their precursors (6a, 6b, 6d, and 6e) with flexible bulky hydrophobic groups instead of the rigid polyheterocyclic moieties. In silico docking confirmed the ability of 5a-5g to bind to the active site of influenza A CEN (PDB code: 6FS6) like baloxavir acid, 3. These novel compounds inhibited polymerase complex activity, inhibited virus replication in cells, prevented death in a lethal influenza A virus mouse challenge model, and dramatically lowered viral lung titers. 5a and 5e potently inhibited different influenza genera in vitro. Precursors 6a and 6d demonstrated impressive mouse oral bioavailability with 6a, providing effective in vivo protection. Thus, these novel compounds are potent CEN inhibitors with in vitro and in vivo activity comparable to baloxavir.
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PMID:Non-rigid Diarylmethyl Analogs of Baloxavir as Cap-Dependent Endonuclease Inhibitors of Influenza Viruses. 3278 99