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)

Azotobacter vinelandii NMN glycohydrolase [EC 3.2.2.14] has been shown to require absolutely GTP or a high-molecular-weight and heat-stable component for its function. The intracellular activator could be purified from its sonicate by heat treatment, acetone precipitation, phenol extraction, and acid precipitation in a good yield. The purified activator showed high affinity and effectiveness for NMN glycohydrolase (KA = 0.012 optical density unit at 257 nm/ml; Vmax standardized by the activity at 1 mM GTP = 88%). Negative cooperativity of the enzyme activation with the activator was also shown. On treatment with either micrococcal nuclease or pancreatic RNase, the activator activity was completely abolished, whereas pronase and trypsin had no effect. The activator could be replaced by yeast RNA as well as calf liver RNA, whereas DNAs purified from Micrococcus lysodeikticus, T 7 and calf thymus had no effect on the enzyme. Furthermore, poly(G) and poly(I) could function as activators with the same effectiveness as the purified activator, and the enzyme activation with these RNA homopolymers was inhibited by poly(C), suggesting that the activation mechanism is specific with respect to base composition. Based on a kinetic analysis of the enzyme activation with commercial RNAs, together with the results from enzymatic digestion, specific inhibition of the enzyme by spermine, and its chemical properties, the activator was identified as an RNA. A model is described for NMN glycohydrolase regulation in which the RNA activator plays an important role in the NMN salvage cycles.
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PMID:Isolation and characterization of an activator for Azotobacter vinelandii nicotinamide mononucleotide glycohydrolase. 243 4

The phosphorylation of the proteins of heterogeneous nuclear ribonucleoprotein particles has been investigated in HeLa cells. 32Pi labeling of intact cells indicated that, of the six major particle proteins, the most heavily phosphorylated was the C1-protein (Mr = 42,000). This protein, together with C2 (Mr = 44,000), is also phosphorylated by [gamma-32P]ATP in particle extracts and in particles that are purified by sedimentation or exclusion chromatography. The C-proteins, together with their particle-associated kinase, were partially purified from isolated particles following dissociation with micrococcal nuclease. Proteins C1 and C2 co-purify on phosphocellulose chromatography, and their peak overlaps with that of a casein kinase activity. Evidence suggesting that this kinase activity is responsible for C-protein phosphorylation includes 1) the phosphorylation of C-proteins in the fractions where they overlap with the kinase, 2) the phosphorylation of added C-protein by fractions of the casein kinase which lack detectable C-protein, and 3) the similarities in catalytic properties of the casein kinase- and C-protein-phosphorylating activities. The purified kinase activity is cyclic nucleotide and Ca2+ independent. It is stimulated by polyamines, inhibited by heparin, and utilizes either GTP or ATP with high affinity. Serine residues are the major phosphate acceptors. These properties indicate that the kinase is casein kinase II or a closely related enzyme. Moreover, purified casein kinase II from rabbit liver effectively phosphorylates C-protein. These results suggest that C-proteins may be natural substrates for nuclear casein kinase II.
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PMID:Phosphorylation of the C-proteins of HeLa cell hnRNP particles. Involvement of a casein kinase II-type enzyme. 642 27

A heme-controlled inhibitor of translation was isolated from the S-100 of rabbit reticulocytes by a novel procedure including chromatography on double-stranded ribonucleic acid (dsRNA)-cellulose. The inhibitor thus purified is extremely active and functionally resembles previously studied heme-controlled inhibitor preparations in terms of kinetics and extent of inhibition of translation, relief of inhibition by eukaryotic initiation factor 2 (eIF-2), relief of inhibition by 2-aminopurine, and preferential inhibition of alpha-over beta-globin synthesis. The action of this inhibitor on translation is resistant to treatment with bacterial alkaline phosphatase, micrococcal nuclease, or trypsin and to incubation at 95 degrees C, pH 2 or pH 12. The inhibitor not only is retained on DEAE-cellulose, phosphocellulose, and dsRNA-cellulose but also exhibits a high affinity for the dye Cibacron Blue, properties that suggest that it may be a protein. Unlike previously described heme-controlled inhibitor preparations, or preparations that did not pass over dsRNA-cellulose, the inhibitor recovered upon dsRNA-cellulose chromatography does not exhibit eIF-2 kinase activity. The inhibitor does not block ternary complex formation between eIF-2, methionyl-tRNAfMet, and GTP but inhibits the ability of eIF-2 to form a complex with labeled globin mRNA. In the presence of inhibitor, the formation of mRNA/eIF-2 complexes can be restored effectively by an excess of eIF-2 but not by an excess of mRNA. The inhibitor thus appears to block the interaction between eIF-2 and mRNA not by competing with eIF-2 for a binding site on mRNA but, instead, by acting on eIF-2 itself.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Isolation of a heme-controlled inhibitor of translation that blocks the interaction between messenger rna and eukaryotic initiation factor 2. 647 77

An RNA-dependent RNA polymerase (RdRp) activity was detergent-solubilized from the chloroplast membranes of Chinese cabbage leaves infected with turnip yellow mosaic virus (TYMV). The template-dependent, micrococcal nuclease-treated activity synthesized full-length minus strands from TYMV RNA and 3'-fragments as short as a 28-nucleotide-long RNA comprising the amino acid acceptor stem of the 3'-tRNA-like structure (TLS). Minus strands were shown to arise by de novo initiation with the insertion of GTP opposite the penultimate (C) residue of the 3'-terminal -CCA. The TYMV RdRp activity was template specific in that poly(A) RNA was not copied, and alfalfa mosaic virus (AIMV) RNA, which does not contain a 3'-TLS, was a very poor template. However, other viral RNAs with a 3'-TLS and in vitro transcripts of tRNAs were copied to varying degrees. Fully modified tRNAs were either inactive or poorly active templates, and AIMV 3'-RNA, even when provided with a 3'-terminal -ACCA, was not copied detectably. A potential role of the acceptor stem pseudoknot as a promoter element was assessed with mutations that drastically altered the structure and sequence of the pseudoknot, revealing only a twofold effect in decreasing template activity. The data show that RNAs with both a tRNA-like conformation and a -CCA 3'-terminus are potential templates for TYMV RdRp and suggest that promoter elements are not limited to the acceptor stem pseudoknot.
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PMID:Turnip yellow mosaic virus RNA-dependent RNA polymerase: initiation of minus strand synthesis in vitro. 921 66

The 5' cap structure of trypanosomatid mRNAs, denoted cap 4, is a complex structure that contains unusual modifications on the first four nucleotides. We examined the four eukaryotic initiation factor 4E (eIF4E) homologues found in the Leishmania genome database. These proteins, denoted LeishIF4E-1 to LeishIF4E-4, are located in the cytoplasm. They show only a limited degree of sequence homology with known eIF4E isoforms and among themselves. However, computerized structure prediction suggests that the cap-binding pocket is conserved in each of the homologues, as confirmed by binding assays to m(7)GTP, cap 4, and its intermediates. LeishIF4E-1 and LeishIF4E-4 each bind m(7)GTP and cap 4 comparably well, and only these two proteins could interact with the mammalian eIF4E binding protein 4EBP1, though with different efficiencies. 4EBP1 is a translation repressor that competes with eIF4G for the same residues on eIF4E; thus, LeishIF4E-1 and LeishIF4E-4 are reasonable candidates for serving as translation factors. LeishIF4E-1 is more abundant in amastigotes and also contains a typical 3' untranslated region element that is found in amastigote-specific genes. LeishIF4E-2 bound mainly to cap 4 and comigrated with polysomal fractions on sucrose gradients. Since the consensus eIF4E is usually found in 48S complexes, LeishIF4E-2 could possibly be associated with the stabilization of trypanosomatid polysomes. LeishIF4E-3 bound mainly m(7)GTP, excluding its involvement in the translation of cap 4-protected mRNAs. It comigrates with 80S complexes which are resistant to micrococcal nuclease, but its function is yet unknown. None of the isoforms can functionally complement the Saccharomyces cerevisiae eIF4E, indicating that despite their structural conservation, they are considerably diverged.
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PMID:Binding specificities and potential roles of isoforms of eukaryotic initiation factor 4E in Leishmania. 1704 Nov 89

The global regulator CodY controls the expression of dozens of metabolism and virulence genes in the opportunistic pathogen Staphylococcus aureus in response to the availability of isoleucine, leucine and valine (ILV), and GTP. Using RNA-Seq transcriptional profiling and partial activity variants, we reveal that S. aureus CodY activity grades metabolic and virulence gene expression as a function of ILV availability, mediating metabolic reorganization and controlling virulence factor production in vitro. Strains lacking CodY regulatory activity produce a PIA-dependent biofilm, but development is restricted under conditions that confer partial CodY activity. CodY regulates the expression of thermonuclease (nuc) via the Sae two-component system, revealing cascading virulence regulation and factor production as CodY activity is reduced. Proteins that mediate the host-pathogen interaction and subvert the immune response are shut off at intermediate levels of CodY activity, while genes coding for enzymes and proteins that extract nutrients from tissue, that kill host cells, and that synthesize amino acids are among the last genes to be derepressed. We conclude that S. aureus uses CodY to limit host damage to only the most severe starvation conditions, providing insight into one potential mechanism by which S. aureus transitions from a commensal bacterium to an invasive pathogen.
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PMID:A spectrum of CodY activities drives metabolic reorganization and virulence gene expression in Staphylococcus aureus. 2711 38