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

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Query: EC:3.1.27.4 (ribonuclease)
6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new ribonuclease called RNase N was isolated from Escherichia coli. It is a nonspecific endoribonuclease that can cleave rRNA, poly(U), and poly(C) to small oligonucleotides and 5'-mononucleotides. It requires monovalent cations and is inhibited by divalent cations. It is suggested that this enzyme plays a role in the decay of rRNA,under various starvation conditions and perhaps in the decay of mRNA.
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PMID:A new endoribonuclease from Escherichia coli. Ribonuclease N. 1 74

Studies using isogenic transductant strains mlpA+ and mlpA as well as reversion analysis suggested that the physiological consequences of a structural gene mutation in murein lipoprotein include (i) increased sensitivity toward chelating agents ethylenediaminetetraacetic acid and ethyleneglycol-bis (beta-aminoethyl ether)-N,N-tetraacetic acid, (ii) leakage of periplasmic enzyme ribonuclease, (iii) weakened association between the outer membrane and the rigid layer accentuated by Mg2+ starvation, resulting in the formation of outer membrane blebs, and (iv) decreased growth rate in media of low ionic strength or low osmolarity. It is suggested that the bound form of lipoprotein plays an important role in the maintenance of the structural integrity of the outer membrane of the Escherichia coli cell envelope. Other outer membrane components may also contribute to the anchorage of outer membrane to the rigid layer, probably through ionic interactions with divalent cations. Using the phenotype of ribonuclease leakage as an unselected marker in a three-factor cross with P1 transduction, we were able to establish the gene order of man mlpA aroD pps on the E. coli chromosome.
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PMID:Physiological characterization of an Escherichia coli mutant altered in the structure of murein lipoprotein. 41 67

In previous studies, brains but not hearts of intact early chick embryos were found to be sensitive to protein starvation. In this study, the in vitro protein synthetic activity of polysomes isolated from brains was found to be greater than those isolated from hearts. Starvation reduced the protein synthetic activity of polysomes in vitro but the extent of the reduction was approximately the same for both brains and hearts. A reduction in the amount of ribosomes as polysomes may have contributed to the lower synthetic activity of polysomes from tissues of starved embryos but not to the differences in synthetic activities between brains and hearts. In addition, neither the stability of isolated polysomes nor ribosome-associated ribonuclease activity appeared responsible for the differences observed in polysome synthetic activities. In direct relationship to the differential sensitivity of brains and hearts to starvation observed in the intact embryo, ribosomes isolated from brains of both growing and starved embryos were more readily degraded during in vitro incubation than those from hearts.
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PMID:Polysome activity in relation to growth and protein starvation in brains and hearts of cultured early chick embryos. 56 60

Two criteria are suggested for assessing the relevance of biochemical events occurring early in sporulation. The first is thymidine starvation, a condition known to inhibit sporulation. This also inhibits the production of metalloprotease, serine protease, and ribonuclease; alpha-amylase production, however, is unaffected. The second is the effect of a regulator mutation which increases the production of the proteases. In the mutant, ribonuclease is produced in correspondingly large quantities whereas alpha-amylase production is unaffected. We conclude that, whereas the serine protease is part of the main sequence of events leading to formation of the spore, the metalloprotease is a side effect, i.e., connected with the main sequence but not part of it. Ribonuclease could, on present evidence, be either in the main sequence or a side effect associated with it. Amylase, however, seems to be separately regulated and neither directly nor indirectly connected with the sporulation sequence.
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PMID:Criteria for categorizing early biochemical events occurring during sporulation of Bacillus subtilis. 80 78

Cytochrome c, a "mobile electron carrier" of the mitochondrial respiratory chain, also occurs in detectable amounts in the cytosol, and can receive electrons from cytochromes present in endoplasmic reticulum and plasma membranes as well as from superoxide and ascorbate. The pigment was found to dissociate from mitochondrial membranes in liver and kidney when rats were subjected to heat exposure and starvation, respectively. Treating cytochrome c with hydroxylamine gives a partially deaminated product with altered redox properties; decreased stimulation of respiration by deficient mitochondria, increased reduction by superoxide, and complete loss of reducibility by plasma membranes. Mitochondria isolated from brown adipose tissue of cold-exposed rats are found to be sub-saturated with cytochrome c. The ability of cytochrome c to reactivate reduced ribonuclease is now reinterpreted as a molecular chaperone role for the hemoprotein.
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PMID:Functions of cytochrome c in regulation of electron transfer and protein folding. 132 35

Axenic Tetrahymena pyriformis, syngen 1, mating type II cells were grown in Cox's defined medium. When washed and transferred into nonnutrient dilute salt solution or resuspended in the defined medium, the intact cells secrete acid hydrolases into the medium. Cells starving in the salt solution release in 5 hr about two-thirds of their beta-glucosidase, beta-N-acetylglucosaminidase, alpha-glucosidase, and amylase activities, about one-third of their deoxyribonuclease and phosphatase activities, smaller amounts of ribonuclease, and only a negligible fraction of their proteinase activity and protein content. During this period there is practically no change in the enzyme activities (except for a sudden increase of ribonuclease activity) and protein content of cells and medium together. Cells resuspended in the nutrient medium secrete enzymes as do the starved cells, but replace this loss, so that there is a continuous increase of the activities in the total system. According to isopycnic centrifugation experiments performed in sucrose gradients, the source of the hydrolases is a special population of lysosomes which disappear from the cells during starvation. This population equilibrates in the high density region of the gradients and contains the various acid hydrolases in about the proportion in which these enzymes appear in the medium.
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PMID:Secretion of acid hydrolases and its intracellular source in Tetrahymena pyriformis. 433 53

Log-phase Tetrahymena were washed and resuspended in a dilute salt solution supplemented with glucose, acetate, pyruvate, or carmine, as desired, and then incubated for 5 h. Intra- and extracellular activities of acid phosphatase, alpha-glucosidase, and ribonuclease were assayed. Extracellular activities were corrected for proteolytic degradation. The three nutritive substrates affected both the amount and pattern of extracellular enzyme release, but carmine had no effect. Intracellular activities declined early in the starvation period, but partially recovered with time, particularly alpha-glucosidase activity. Acetate reduced the decline in acid phosphatase activity; acetate and glucose enhanced the recovery of alpha-glucosidase activity; carmine had no effect on intracellular enzyme activities. Protein content changed little and was unaffected by the addition of substrates. Glycogen content increased during incubation; acetate and glucose enhanced the increase.
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PMID:Lysosomal physiology in Tetrahymena. I. Effect of glucose, acetate, pyruvate, and carmine on intracellular content and extracellular release of three acid hydrolases. 463 42

The influence of amino acid starvation on polysome content was examined in relaxed and stringent strains of Escherichia coli which were isogenic for the RC locus. No difference was observed between the polysome profiles obtained from two different sets of stringent and relaxed strains starved for the same amino acid. In both relaxed and stringent strains, starvation for amino acids other than methionine resulted in only a slight breakdown of polysomes with a concomitant increase of 70S ribosomes. However, starvation for methionine in both RC stringent and relaxed strains of E. coli resulted in a more extensive degradation of polysomes and accumulation of 70S ribosomes. The 70S ribosomes obtained as a result of methionine starvation were more sensitive to degradation to 50 and 30S subunits in 10(-3)m Mg(2+) than 70S monomers obtained either by degradation of polysomes with ribonuclease or by starvation of cells for amino acids other than methionine. The 70S ribosomes from methionine starvation were similar (sensitivity to 10(-3)m Mg(2+)) to 70S ribosomes obtained from cells in which initiation of protein synthesis had been prevented by trimethoprim, an inhibitor of formylation. Since N-formyl-methionyl-transfer ribonucleic acid is required for initiation, the 70S ribosomes obtained in both methionine-starved and trimethoprim-treated cells must result from association of 50 and 30S subunits for reasons other than reinitiation. These results suggest that the level of ribonucleic acid synthesis does not influence the distribution of ribosomes in the polysome profile and vice versa.
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PMID:Polysome stability in relaxed and stringent strain of Escherichia coli during amino acid starvation. 491 72

The decline in colony-forming ability observed during tryptophan starvation of Bacillus subtilis auxotrophs is a concentration-dependent phenomenon. It does not manifest itself when the initial cell concentration is 10(6) cells/ml or lower. This property has been used to test the killing activity of different fractions of the dying cells. Most of the activity recovered is found in the supernatant fluid of the starved culture. Sensitive and resistant strains can be identified. Active supernatant fluids can only be isolated from tryptophan auxotrophs sensitive to tryptophanless death. Resistant cells neither produce nor respond to the factor, and sensitive cells respond only when deprived of tryptophan. The killing activity is continuously produced and released into the medium at least up to 4 hr after removal of tryptophan from the culture. The killing activity is deoxyribonuclease-, ribonuclease-, and heat-resistant.
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PMID:Partial characterization of the factor responsible for tryptophanless death in Bacillus subtilis. 498 70

1. A centrifugation method for the fractionation of the postmitochondrial fraction from rat-liver homogenates is described. The technique, in which no detergent is used, may be used as a tool to discriminate between two classes of ribosomes. One class is firmly bound to membranes and the other consists either of free polysomes or of ribosomes attached by weaker forces to the membranes of the endoplasmic reticulum. 2. Electron-micrograph studies revealed that the polysomes were not contaminated with bound ribosomes or with membranous fragments. 3. The separated fractions were characterized by their RNA, protein, ribonuclease and phospholipid content. 4. The influence of starvation on the RNA and protein contents of the different fractions was investigated. 5. Labelling of the various centrifugal fractions in vivo revealed no difference in uptake of radioactive amino acid between the two classes of ribosomes. 6. Incorporation of radioactive leucine in vitro and the polyuridylic acid-directed phenylalanine incorporation were similar for both classes of ribosomes.
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PMID:Isolation and properties of polyribosomes and fragments of the endoplasmic reticulum from rat liver. 603 56


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