Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.8 (polynucleotide phosphorylase)
 723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The complexed 70S ribosomes (monosomes) that accumulate in Escherichia coli after an energy source shift-down were examined in an electron microscope. In all cases, the ribosomes lie at or near one end of a ribonucleic acid (RNA) strand. This messenger RNA (mRNA) has a mean length of 168 nm and a length-average length of 200 nm, sufficient to code for polypeptides of a weight-average molecular weight of 20,000. The length distribution indicates that these strands are a reasonable representation of the population of monocistronic mRNA's of E. coli. The mRNA strands disappear entirely upon digestion with pancreatic ribonuclease, phosphodiesterase I, or polynucleotide phosphorylase. The susceptibility to digestion by 3'-exonucleases indicate that the ribosomes lie at the 5' end of the mRNA strands. These results are consistent with the hypothesis that down-shifted cells have a translational defect at a point subsequent to the binding of ribosomes to mRNA but prior to the formation of the first peptide bond, such that ribosomes remain bound at or near their points of initial attachment to mRNA.
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PMID:Association of messenger ribonucleic acid with 70S monosomes from down-shifted Escherichia coli. 17 81

The disappearance of ribosomes in Escherichia coli cells starved for a carbon source was studied. We used a series of mutants, some of them lacking in ribonuclease I(RNase I, EC 2.7.7.17), and other containing various combinations of modified polynucleotide phosphorylase (PNPase, EC 2.7.7.8) and modified ribonuclease II (RNase II, EC 3.1.4.1). RNA was prepared from the starved mutant cells and separated on polyacrylamide gels. The results obtained indicate that 23 S RNA degradation is similar in all strains that lack RNase I, and is slightly increased in the strain that contains this enzyme. The extent of 16 S RNA degradation is identical in all strains tested. RNA species in the size of 4 S and smaller accumulate in mutants containing modified forms of PNPase and RNase II. The appearance of an RNA species 10% smaller than 16 S RNA (d16 S RNA) was observed in all strains that contain unmodified RNase II. Analysis of ribosomes and polysomes and their RNA content indicated that polysomes are converted to monosomes and these, in turn, to ribosomal subunits. No RNA degradation products were found in polysomes, 70 S, OR 50 C particle; 30 S subunits contained 16 S RNA as well as the d16 S RNA species. Subunits are degraded to a similar extent in all strains lacking RNase I, and at a slightly faster rate in the strain that contains RNase I. The RNA to protein ratio in subunits prepared from starved cells is similar to that of unstarved cultures. Very little degradation of ribosomal proteins occurs in these mutants during carbon starvation. The proteins released from degraded ribosomes are found in the fast sedimenting (20,000 times g) pellet. Cell viability studies indicated a direct correlation between the capacity of the mutants to recovery from starvation and their capacity to degrade RNA. Thus a biological necessity for degradation of ribosomes during starvation is implied. Based on these data we propose that the endonucleolytic degradation of ribosomal RNA is the primary event in starvation degradation. It takes place in ribosomal subunits, which fall apart after the endonucleoltic attack. The RNA pieces produced by this cleavage are degraded to nucleotide by RNase II and PNPase. The ribosomal proteins attach to the cell membrane.
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PMID:The fate of ribosomes in Escherichia coli cells starved for a carbon source. 108 66

A number of "surface" enzymes of Escherichia coli (i.e., among those selectively released by osmotic shock) all displayed higher specific activities in extracts of minicells than in extracts of typical rod forms; these enzymes included alkaline phosphatase, cyclic phosphodiesterase, acid hexose monophosphatase, 5'-nucleotidase, and ribonuclease I. In addition, alkaline phosphatase, cyclic phosphodiesterase, and acid hexose monophosphatase were cytochemically localized to regions of minicell periplasm that resembled reactive polar enlargements of the periplasm in rod forms. In contrast, a number of "internal" cytoplasmic enzymes (inorganic pyrophosphatase, beta-galactosidase, glutamine synthetase, polynucleotide phosphorylase, and ribonuclease II) showed elevated or similar specific activities in extracts of rod forms versus extracts of minicells. A specific heat-labile inhibitor for 5'-nucleotidase, known to occur in the cytoplasm, also showed no enrichment in minicells. These findings indicate that the "surface" enzymes are segregated in vivo into the terminal minicell buds, possibly because these enzymes are concentrated in the polar enlargements of the periplasm in typical rod forms.
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PMID:Biochemical and cytochemical evidence for the polar concentration of periplasmic enzymes in a "minicell" strain of Escherichia coli. 431 25

CsgD and cyclic-3',5'-di-guanylate are key regulators of biofilm formation in Salmonella enterica serovar Typhimurium. Our results show that polynucleotide phosphorylase and NlpI oppositely altered expression of CsgD. Polynucleotide phosphorylase and NlpI also had opposite effects on the expression of yjcC, which codes for a cyclic-3',5'-di-guanylate phosphodiesterase affecting CsgD expression.
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PMID:Opposing contributions of polynucleotide phosphorylase and the membrane protein NlpI to biofilm formation by Salmonella enterica serovar Typhimurium. 2107 29

We previously identified CvfA (SA1129) as a Staphylococcus aureus virulence factor using a silkworm infection model. S. aureus cvfA-deleted mutants exhibit decreased expression of the agr locus encoding a positive regulator of hemolysin genes and decreased hemolysin production. CvfA protein hydrolyzes a 2',3'-cyclic phosphodiester bond at the RNA 3' terminus, producing RNA with a 3'-phosphate (3'-phosphorylated RNA, RNA with a 3'-phosphate). Here, we report that the cvfA-deleted mutant phenotype (decreased agr expression and hemolysin production) was suppressed by disrupting pnpA-encoding polynucleotide phosphorylase (PNPase) with 3'- to 5'-exonuclease activity. The suppression was blocked by introducing a pnpA-encoding PNPase with exonuclease activity but not by a pnpA-encoding mutant PNPase without exonuclease activity. Therefore, loss of PNPase exonuclease activity suppressed the cvfA-deleted mutant phenotype. Purified PNPase efficiently degraded RNA with 2',3'-cyclic phosphate at the 3' terminus (2',3'-cyclic RNA), but it inefficiently degraded 3'-phosphorylated RNA. These findings indicate that 3'-phosphorylated RNA production from 2',3'-cyclic RNA by CvfA prevents RNA degradation by PNPase and contributes to the expression of agr and hemolysin genes. We speculate that in the cvfA-deleted mutant, 2',3'-cyclic RNA is not converted to the 3'-phosphorylated form and is efficiently degraded by PNPase, resulting in the loss of RNA essential for expressing agr and hemolysin genes, whereas in the cvfA/pnpA double-disrupted mutant, 2',3'-cyclic RNA is not degraded by PNPase, leading to hemolysin production. These findings suggest that CvfA and PNPase competitively regulate RNA degradation essential for S. aureus virulence.
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PMID:CvfA protein and polynucleotide phosphorylase act in an opposing manner to regulate Staphylococcus aureus virulence. 2449 13

The Escherichia coli operon dosCP, also called yddV-yddU, co-expresses two heme proteins, DosC and DosP, both of which are direct oxygen sensors but paradoxically have opposite effects on the levels of the second messenger c-di-GMP. DosC is a diguanylate cyclase that synthesizes c-di-GMP from GTP, whereas DosP is a phosphodiesterase that linearizes c-di-GMP to pGpG. Both proteins are associated with the large degradosome enzyme complex that regulates many bacterial genes post-transcriptionally by processing or degrading the corresponding RNAs. Moreover, the c-di-GMP directly binds to PNPase, a key degradosome enzyme, and enhances its activity. This review combines biochemical, biophysical, and genetic findings on DosC and DosP, a task that has not been undertaken until now, partly because of the varied nomenclature. The DosC and DosP system is examined in the context of the current knowledge of degradosomes and considered as a possible prototype for the compartmentalization of sensing by E. coli.
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PMID:Escherichia coli DosC and DosP: a role of c-di-GMP in compartmentalized sensing by degradosomes. 3165 42