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
Query: EC:2.7.7.6 (
RNA polymerase
)
34,946
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Probably the oldest and most widespread antimicrobial strategy in living organisms is the use of antimicrobial peptides. Bacteria secrete such defence peptides, termed bacteriocins, that they use for microbial competitions. Microcins are bacteriocins of less than 10 kDa produced by Escherichia coli and related enterobacteria through the ribosomal pathway. They are synthesized as linear precursors, which can further undergo complex post-translational modifications resulting from dedicated maturation enzymes encoded in the microcin gene clusters, and are processed by proteolytic cleavage. Microcins exert potent bactericidal activities that use subtle and clever mechanisms to cross outer and inner membranes of Gram-negative bacteria. To cross the outer membrane, siderophore-microcins hijack receptors involved in iron acquisition. The lasso-peptide microcin J25, which is characterized by a knotted arrangement where the C-terminal tail is threaded through an N-terminal macrolactam ring, uses a hydroxamate siderophore receptor and the inner-membrane protein SbmA for import in sensitive bacteria, where it inhibits bacterial transcription through binding to RNAP (
RNA polymerase
). Microcin C produced as a heptapeptide
adenylate
, requires an outer-membrane porin and an inner-membrane ABC (ATP-binding-cassette) transporter to reach the cytoplasm of target bacteria, where it is processed by proteases into a non-hydrolysable aspartyl-
adenylate
analogue. Therefore, despite showing different killing mechanisms and the absence of any structural homology, microcins have the common characteristic to use Trojan horse strategies to destroy their competitors. They offer new and promising tracks for further design and engineering of novel efficient antibiotics.
...
PMID:Microcins in action: amazing defence strategies of Enterobacteria. 2317 98
N
6
-methylated adenine (m
6
A) is the most frequent posttranscriptional modification in eukaryotic mRNA. Turnover of RNA generates N
6
-methylated AMP (N
6
-mAMP), which has an unclear metabolic fate. We show that
Arabidopsis thaliana
and human cells require an N
6
-mAMP deaminase (ADAL, renamed MAPDA) to catabolize N
6
-mAMP to inosine monophosphate in vivo by hydrolytically removing the aminomethyl group. A phylogenetic, structural, and biochemical analysis revealed that many fungi partially or fully lack MAPDA, which coincides with a minor role of N
6
A-RNA methylation in these organisms. MAPDA likely protects RNA from m
6
A misincorporation. This is required because eukaryotic
RNA polymerase
can use N
6
-mATP as a substrate. Upon abrogation of
MAPDA
, root growth is slightly reduced, and the N
6
-methyladenosine, N
6
-mAMP, and N
6
-mATP concentrations are increased in Arabidopsis. Although this will potentially lead to m
6
A misincorporation into RNA, we show that the frequency is too low to be reliably detected in vivo. Since N
6
-mAMP was severalfold more abundant than N
6
-mATP in
MAPDA
mutants, we speculate that additional molecular filters suppress the generation of N
6
-mATP. Enzyme kinetic data indicate that
adenylate
kinases represent such filters being highly selective for AMP versus N
6
-mAMP phosphorylation. We conclude that a multilayer molecular protection system is in place preventing N
6
-mAMP accumulation and salvage.
...
PMID:m
6
A RNA Degradation Products Are Catabolized by an Evolutionarily Conserved N
6
-Methyl-AMP Deaminase in Plant and Mammalian Cells. 2990 27
Coronavirus nonstructural protein 8 (nsp8) has been suggested to have diverse activities, including noncanonical template-dependent polymerase activities. Here, we characterized a recombinant form of the human coronavirus 229E (HCoV-229E) nsp8 and found that the protein has metal ion-dependent RNA 3'-terminal adenylyltransferase (TATase) activity, while other nucleotides were not (or very inefficiently) transferred to the 3' ends of single-stranded and (fully) double-stranded acceptor RNAs. Using partially double-stranded RNAs, very efficient TATase activity was observed if the opposite (template) strand contained a short 5' oligo(U) sequence, while very little (if any) activity was detected for substrates with other homopolymeric or heteropolymeric sequences in the 5' overhang. The oligo(U)-assisted/templated TATase activity on partial-duplex RNAs was confirmed for two other coronavirus nsp8 proteins, suggesting that the activity is conserved among coronaviruses. Replacement of a conserved Lys residue with Ala abolished the
in vitro
RNA-binding and TATase activities of nsp8 and caused a nonviable phenotype when the corresponding mutation was introduced into the HCoV-229E genome, confirming that these activities are mediated by nsp8 and critical for viral replication. In additional experiments, we obtained evidence that nsp8 has a pronounced specificity for
adenylate
and is unable to incorporate guanylate into RNA products, which strongly argues against the previously proposed template-dependent
RNA polymerase
activity of this protein. Given the presence of an oligo(U) stretch at the 5' end of coronavirus minus-strand RNAs, it is tempting to speculate (but remains to be confirmed) that the nsp8-mediated TATase activity is involved in the 3' polyadenylation of viral plus-strand RNAs.
IMPORTANCE
Previously, coronavirus nsp8 proteins were suggested to have template-dependent
RNA polymerase
activities resembling those of RNA primases or even canonical RNA-dependent RNA polymerases, while more recent studies have suggested an essential cofactor function of nsp8 (plus nsp7) for nsp12-mediated RNA-dependent RNA polymerase activity. In an effort to reconcile conflicting data from earlier studies, the study revisits coronavirus nsp8-associated activities using additional controls and proteins. The data obtained for three coronavirus nsp8 proteins provide evidence that the proteins share metal ion-dependent RNA 3' polyadenylation activities that are greatly stimulated by a short oligo(U) stretch in the template strand. In contrast, nsp8 was found to be unable to select and incorporate appropriate (matching) nucleotides to produce cRNA products from heteropolymeric and other homooligomeric templates. While confirming the critical role of nsp8 in coronavirus replication, the study amends the list of activities mediated by coronavirus nsp8 proteins in the absence of other proteins.
...
PMID:Identification and Characterization of a Human Coronavirus 229E Nonstructural Protein 8-Associated RNA 3'-Terminal Adenylyltransferase Activity. 3091 70
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