Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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

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