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:3.1.26.9 (ribonuclease)
6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An endoribonuclease which cleaves only single-stranded RNA has been purified from nucleoli of Ehrlich ascites tumor cells. The molecular weight of the ribonuclease is 50,000 to 52,000 as estimated from sedimentation in glycerol density gradients and by gel filtration on Sephadex G-100. The endoribonuclease requires Mg2+ or Mn2+ (0.2 mM) for optimum activity. Monovalent cations including K+, Na+, and NH+4 are inhibitory. The ribonuclease gave an apparent Km for single-stranded RNA of 30 microM. Using ribohomopolymers, we found that the enzyme could digest single-stranded, poly(C), poly(U), and poly(A) equally well, but would not degrade duplex poly(C) . poly(I) or poly(A) . poly(U). The lack of base specificity was further demonstrated using RNA sequence analysis of partial digest products of yeast 5.8 S RNA. The ribonuclease activity is sensitive to EDTA and N-ethylmaleimide, but is not inhibited by human placental RNase inhibitor. The enzyme makes endonucleolytic cleavages which generate 5'-phosphate-terminated oligonucleotides.
...
PMID:Isolation and characterization of a single-stranded specific endoribonuclease from Ehrlich cell nucleoli. 714 16

The largest and smallest discrete forms of the estrogen receptor in human breast tumor cytosol were characterized by competitive steroid binding, ultracentrifugation, gel filtration, and electrophoresis in polyacrylamide gels of several concentrations. Incubation of cytosol with [3H]estradiol and centrifugation in glycerol gradients containing 20 mM Na2MoO4 and 0 or 150 mM KCl revealed a 9-10S form of the receptor. It resembles the molybdate-stabilized complexes in cytosols of other human and rodent, malignant and healthy tissues, and the complex detected in breast tumor cytosol containing leupeptin, a bacterial protease inhibitor. Preservation of receptor integrity during purification and discrimination from serum steroid-binding components are facilitated by inclusion of molybdate in all buffers. Possible mechanisms of action of molybdate include the inhibition of ribonuclease action on RNA-associated receptor forms and protection against specific proteolytic cleavage by stabilization of a phosphate group on the vulnerable residue or a neighboring one. During fractionation of tumor cytosol in the absence of molybdate, the receptor is converted to a mixture of fragments. The smallest that retains the bound steroid, the mero-receptor, resembles the products of endogenous and exogenous protease action on receptors for all classes of steroids in a wide range of tissues. The similarities between both the largest and the smallest known forms of the breast tumor estrogen receptor and corresponding forms of other receptors support the notion of the common architecture of steroid receptors in normal and malignant tissues of diverse origins.
...
PMID:Human breast tumor estrogen receptor: effects of molybdate and electrophoretic analyses. 747 73

Ro small ribonucleoprotein complexes (RoRNPs) are thought to comprise several proteins, including the 60-kD Ro and the 52-kD Ro proteins, and several small RNAs, designated Y RNAs. Although RoRNPs are fairly ubiquitous in nature, their precise composition remains unknown, their function has been elusive, and their intracellular localization has been controversial. We have analyzed HeLa cell extracts by glycerol density gradient fractionation in order to determine the distribution of the individual protein and RNA components of RoRNPs. We found that 52-kD Ro was not detectable in an RNP complex with the 60-kD protein under a variety of conditions. Pretreatment of cell extracts with ribonuclease affected gradient migration of the 60-kD but not the 52-kD protein, suggesting that the latter is not complexed with RNA. The migration of the hY RNAs in these gradients closely followed that of 60-kD and not 52-kD Ro. Immunofluorescence analysis of two different cell lines with monospecific antibodies against 52- and 60-kD proteins strongly suggests that these two proteins are not present on overlapping sets of structures in vivo. We conclude that the 52-kD Ro protein is not a detectable component of the RoRNP complex under these conditions despite its reactivity with Ro autoimmune antisera.
...
PMID:Molecular composition of Ro small ribonucleoprotein complexes in human cells. Intracellular localization of the 60- and 52-kD proteins. 751 86

A small plastid-encoded RNA (spRNA, 218 nt) has been detected in tobacco. The corresponding locus (sprA) does not contain any open reading frame and is actively transcribed from its own promoter, as shown by ribonuclease protection assays using in vitro capped RNAs. Gel-shift and UV-crosslinking experiments showed the formation of a specific complex between spRNA and chloroplast polypeptides. The mobility of the complex was further shifted when a transcript bearing part of the 16S rRNA leader sequence was added to the incubation mixture. Glycerol gradient fractionation of a chloroplast lysate indicated a preferential sedimentation of spRNA at 15-20S and 70S. These observations, and the potential base-pairing with the leader sequence of pre-16S rRNA, suggest a role for spRNA in chloroplast ribosome biogenesis, i.e. 16S rRNA maturation. By sequencing of tomato plastid DNA and heterologous northern hybridizations, the presence of sprA homologs and their expression in a number of dicot plants have also been shown.
...
PMID:A novel RNA gene in the tobacco plastid genome: its possible role in the maturation of 16S rRNA. 751 32

A nucleolar endoribonuclease from mouse Ehrlich ascites tumor cells, that has been implicated in the endonucleolytic cleavage of mouse precursor ribosomal RNA, specifically and stably binds an in vitro-derived rRNA transcript containing the +650 early processing site. The specificity of binding was demonstrated by mobility shift analysis, glycerol gradient velocity sedimentation analysis, and UV-crosslinking studies. Binding did not require Mg2+ and therefore was not dependent on cleavage; however, binding was dependent on the presence of the early +650 processing site since a pre-rRNA transcript with the +650 processing site deleted failed to compete in binding. A small nucleolar RNA component was not required for the formation of this stable complex or for the specific cleavage of a processing competent pre-rRNA transcript. UV crosslinking studies using 32P-labeled 5-azidouridine-substituted pre-rRNA with bound nucleolar endoribonuclease identified three closely sized polypeptides of approximately 50, approximately 48, and approximately 45 kDa, respectively, that specifically crosslinked to the processing competent rRNA transcript. These three polypeptides species were identified following ribonuclease digestion and electrophoresis on a SDS-polyacrylamide gel. An identical pattern of labeled polypeptides was also identified from gel mobility shift analysis where the specifically shifted material was U.V. crosslinked. The largest of these polypeptides corresponded to the estimated size of the nucleolar endoribonuclease, while the lower molecular weight species may represent partially proteolyzed enzyme. Overall, these results suggest that the unique specificity of the nucleolar endoribonuclease may, in part, be attributed to the formation of a stable complex at the +650 processing site for mouse preribosomal RNA, and that formation of this unique stable complex affords a means to specifically label the limited amount of available partially purified enzyme for sequence analysis.
...
PMID:Selection of a preribosomal RNA processing site by a nucleolar endoribonuclease involves formation of a stable complex. 828 28

Mitochondrial ribonuclease (RNase) P from Aspergillus nidulans was purified to near homogeneity using whole-cell extract as the starting material. A 4400-fold purification with a yield of 5.2% was achieved by ammonium sulfate fractionation, heat treatment, and five types of column chromatography, including tRNA-affinity column chromatography. This enzyme, which has a molecular mass of 232 kDa determined by glycerol gradient sedimentation analysis, appears to be composed of seven polypeptides and an RNA moiety. These seven polypeptides consistently copurified with the RNase P activity through two ion-exchange chromatography columns and in a glycerol gradient. As judged by nuclease sensitivity, the enzyme requires an RNA component for its activity. The 3'-end-labeled RNAs that copurified with the enzyme displayed identical sequences but had variable lengths for the 5' end, indicating that they originated from a common RNA molecule, the putative RNA component of RNase P. The purified enzyme cleaved mitochondrial precursor tRNAHis, resulting in an 8-bp acceptor stem. This implies that the purified RNase P is a mitochondrial enzyme and that an additional guanylate residue (at position -1) of tRNAHis in A. nidulans mitochondria is generated by a mode that is analogous to the generation of their counterparts in prokaryotes and chloroplasts.
...
PMID:Purification and characterization of mitochondrial ribonuclease P from Aspergillus nidulans. 863 44

In Aspergillus nidulans, the nuclear ribonuclease P was separated from its mitochondrial counterpart by Q-Sepharose chromatography, and a precursor-tRNA(His) processing assay system was used to discriminate nuclear ribonuclease P activity from the mitochondrial counterpart. The nuclear ribonuclease P was purified to near homogeneity from whole-cell extracts. A 2150-fold purification with a yield of 2.3% was achieved by five types of chromatography including tRNA affinity chromatography and glycerol gradient velocity sedimentation. This enzyme, which had a molecular mass of 580 kDa determined by both glycerol-gradient sedimentation analysis and gel-permeation chromatography, appeared to be composed of seven polypeptides and an RNA molecule. Seven polypeptides, with masses of 125, 85, 45, 33, 30, 21, 19 kDa, were consistently copurified with nuclear ribonuclease P activity through MonoS and tRNA affinity chromatography and in a glycerol gradient. As judged by a micrococcal-nuclease-sensitivity assay, nuclear ribonuclease P required an RNA component for its activity, as do other ribonuclease Ps. Analysis of the radiolabeled 5' end of RNAs copurified with nuclear ribonuclease P implied that RNA molecules in the purified nuclear ribonuclease P originated from a common RNA molecule, the putative RNA molecule of nuclear ribonuclease P. Comparison of the two ribonuclease Ps in A. nidulans showed that the protein and RNA components of the nuclear ribonuclease P were different from those of the mitochondrial counterpart.
...
PMID:Purification and characterization of the nuclear ribonuclease P of Aspergillus nidulans. 949 90

The Kidd (JK) blood group locus encodes a urea transporter that is expressed on human red cells and on endothelial cells of the vasa recta in the kidney. Here, we report the identification in human erythroblasts of a novel cDNA, designated HUT11A, which encodes a protein identical to the previously reported erythroid HUT11 urea transporter, except for a Lys(44) --> Glu substitution and a Val-Gly dipeptide deletion after proline 227, which leads to a polypeptide of 389 residues versus 391 in HUT11. Genomic typing by polymerase chain reaction and transcript analysis by ribonuclease protection assay demonstrated that HUT11A encodes the true Kidd blood group/urea transporter protein, which carries only 2 Val-Gly motifs. Upon expression at high levels in Xenopus oocytes, the physiological Kidd/urea transporter HUT11A conferred a rapid transfer of urea (which was insensitive to p-chloromercuribenzene sulfonate or phloretin), a high water permeability, and a selective uptake of small solutes including amides and diols, but not glycerol and meso-erythritol. However, at plasma membrane expression levels close to the level observed in the red cell membrane, HUT11A-mediated water transport and small solutes uptake were absent and the urea transport was poorly inhibited by p-chloromercuribenzene sulfonate, but strongly inhibited by phloretin. These findings show that, at physiological expression levels, the HUT11A transporter confers urea permeability but not water permeability, and that the observed water permeability is a feature of the red cell urea transporter when expressed at unphysiological high levels.
...
PMID:At physiological expression levels the Kidd blood group/urea transporter protein is not a water channel. 1051 15

Glucose uptake into adipose and liver cells is known to up-regulate mRNA levels for various lipogenic enzymes such as fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC). To determine whether the hexosamine biosynthesis pathway (HBP) mediates glucose regulation of mRNA expression, we treated primary cultured adipocytes for 18 h with insulin (25 ng/ml) and either glucose (20 mm) or glucosamine (2 mm). A ribonuclease protection assay was used to quantitate mRNA levels for FAS, ACC, and glycerol-3-P dehydrogenase (GPDH). Treatment with insulin and various concentrations of d-glucose increased mRNA levels for FAS (280%), ACC (93%), and GPDH (633%) in a dose-dependent manner (ED50 8-16 mm). Mannose similarly elevated mRNA levels, but galactose and fructose were only partially effective. l-glucose had no effect. Omission of glutamine from the culture medium markedly diminished the stimulatory effect of glucose on mRNA expression. Since glutamine is a crucial amide donor in hexosamine biosynthesis, we interpret these data to mean that glucose flux through the HBP is linked to regulation of lipogenesis through control of gene expression. Further evidence for hexosamine regulation was obtained using glucosamine, which is readily transported into adipocytes where it directly enters the HBP. Glucosamine was 15-30 times more potent than glucose in elevating FAS, ACC, and GPDH mRNA levels (ED50 approximately 0.5 mm). In summary: 1) GPDH, FAS, and ACC mRNA levels are upregulated by glucose; 2) glucose-induced up-regulation requires glutamine; and 3) mRNA levels for lipogenic enzymes are up-regulated by glucosamine. Hyperglycemia is the hallmark of diabetes mellitus and leads to insulin resistance, impaired glucose metabolism, and dyslipidemia. We postulate that disease pathophysiology may have a common underlying factor, excessive glucose flux through the HBP.
...
PMID:Role of hexosamine biosynthesis in glucose-mediated up-regulation of lipogenic enzyme mRNA levels: effects of glucose, glutamine, and glucosamine on glycerophosphate dehydrogenase, fatty acid synthase, and acetyl-CoA carboxylase mRNA levels. 1275 50

An accurate determination of the overall rotation of a protein plays a crucial role in the investigation of its internal motions by NMR. In the present work, an innovative approach to the determination of the protein rotational correlation time tau(R) from the heteronuclear relaxation data is proposed. The approach is based on a joint fit of relaxation data acquired at several viscosities of a protein solution. The method has been tested on computer simulated relaxation data as compared to the traditional tau(R) determination method from T(1)/T(2) ratio. The approach has been applied to ribonuclease barnase from Bacillus amyloliquefaciens dissolved in an aqueous solution and deuterated glycerol as a viscous component. The resulting rotational correlation time of 5.56 +/- 0.01 ns and other rotational diffusion tensor parameters are in good agreement with those determined from T(1)/T(2) ratio.
...
PMID:Determination of protein rotational correlation time from NMR relaxation data at various solvent viscosities. 1563 May 63


<< Previous 1 2 3 Next >>

---