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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The oligonucleotide ppp5'A2'p5'A2'p5'A, known as 2-5A, is a potent translational inhibitor involved in some aspects of interferon action. To explore the specific function of the charged 5'-triphosphate moiety, we prepared a series of congeners in which the 5' region was hypermodified. Thus, uronic acid derivatives were substituted for the 5' terminal adenosine residue of 2-5A. Compounds 9, 10, 11 and 12 carried adenosine 5'-uronic acid, ethyl adenosine 5'-uronate, adenosine 5'-uronamide, and adenosine 5'-(N-ethyl)uronamide, respectively, in place of the 5' terminal adenosine triphosphate moiety of 2-5A. While all the analogues showed some weak interaction with the 2-5A-dependent endonuclease (RNase L), compound 9 showed the strongest binding ability, and while unable to activate the mouse RNase L, could activate human RNase at a concentration 100-fold greater than that required for the parent 2-5A. This result suggests that the function of the 5'(poly)phosphate moiety of 2-5A may be fulfilled by some other anionic moiety.
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PMID:Synthesis and biological activity of uronic acid analogues of 2-5A[5'-O-triphosphoryladenylyl(2----5')adenylyl-(2'----5')adenosine]. 152 4

1. The response to thermal acclimation of five key rate-limiting enzymes of intermediary metabolism and of six degradative enzymes was measured in tissue extracts of adult Drosophila melanogaster which had been acclimated for 4 days to 15, 25 or 30 degrees C. 2. Three enzymes of intermediary metabolism (HK, alpha-GPDH and CO) showed positive thermal compensation, which is the type of response characteristic of the enzymes involved in energy metabolism in vertebrate ectotherms. 3. The data obtained for CS and G6PDH showed no evidence for increased activity of TCA cycle nor of the pentose phosphate pathway upon cold acclimation in D. melanogaster. 4. Two degradative enzymes, ADH and non-specific esterase, showed inverse thermal compensation which is the type of response characteristic of degradative enzymes in vertebrate ectotherms. 5. In contrast to the situation in vertebrate ectotherms, catalase and the three lysosomal enzymes assayed (APH, acid DNase and acid RNase) displayed positive rather than inverse compensation. 6. The results presented here extend the data on the range of D. melanogaster enzymes which show compensation upon thermal acclimation and on the type of acclimation response which occurs.
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PMID:The effect of acclimation temperature on enzyme activity in Drosophila melanogaster. 165 Dec 3

In this study we determined the activity of the rat luteinising hormone-beta gene promoter in a heterologous rat pituitary cell line (GH3 cells). 1.7 kb of LH-beta 5' flanking sequence and the first 5 bp of the 5' untranslated region were ligated to the chloramphenicol acetyltransferase (CAT) receptor gene (LH-beta-CAT) and transiently transfected by calcium phosphate precipitation into subconfluent cultures of GH3 cells. Basal low-level CAT activity was only detected in GH3 cells, being absent in two non-pituitary cell lines (BeWo and HeLa) RNase analysis revealed that mRNA from transfected GH3 cells protected a fragment of labelled antisense probe of correct size for transcription initiation from the LH-beta CAP site, confirming that promoter activity reflected correctly initiated LH-beta-CAT fusion gene transcripts. CAT activity was consistently induced by an average of 3-5-fold from the full-length 1.7 kb promoter, in a dose- and time-dependent manner, by forskolin, dibutyryl cAMP, and 8-bromo cAMP implying presence of a cAMP-responsive cis-acting domain in the LH-beta promoter region. Transfection of deletion mutants delta-615-CAT, delta-385-CAT and delta-250-CAT each reduced forskolin inducibility to 1.7-fold but did not abolish induction completely suggesting a domain between -1.7 and -0.6 kb contained a cAMP-responsive element(s) (CRE). Further deletion of LH-beta 5' flanking sequences to delta-85-CAT restored forskolin induction to wild-type levels (3-5-fold), suggesting the presence of a weak inhibitory element between -600 and -85 kb, and a cAMP-responsive domain in the proximal promoter region. The LH-beta promoter does not contain perfect tandem repeat palindromic CRE DNA sequences, though there are several octanucleotide sequences differing by only 1 bp from AP-2 binding sites, the consensus CRE, and the vasointestinal peptide gene CRE. Although these data suggest that the LH-beta gene is cAMP responsive this is likely mediated by several and complex protein interactions with multiple DNA sequences in the proximal and distal LH-beta promoter enhancer.
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PMID:Expression of luteinising hormone-beta subunit chloramphenicol acetyltransferase (LH-beta-CAT) fusion gene in rat pituitary cells: induction by cyclic 3'-adenosine monophosphate (cAMP). 165 45

A new class of ribozymes produce 2',3'-cyclic phosphate upon self-catalyzed cleavage of RNA molecules, similar to those observed during enzymatic (RNase-catalyzed) as well as non-enzymatic hydrolyses of RNAs. This product suggests that the reaction intermediate/transition state is a pentacoordinated oxyphosphorane. In order to elucidate the energetics of these RNA cleaving reactions, the reaction coordinate has been simulated and a pentacoordinated intermediate has been characterized via ab initio molecular orbital calculations utilizing the dianionic hydrolysis-intermediate of methyl ethylene phosphate as a model compound. The calculated reaction coordinate indicates that the transition state for the P-O(2') bond cleavage is lower in energy than that for the P-O(5') bond cleavage under uncatalyzed conditions. Thus, the dianionic pentacoordinated phosphorus intermediate tends to revert back to the starting RNA by cleaving the P-O(2') bond rather than productively cleaving the P-O(5') bond. In order for ribozymes to effectively cleave RNA molecules, it is therefore mandatory to stabilize the leaving 5'-oxygen, e.g. by means of a divalent magnesium ion.
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PMID:Energetics of RNA cleavage: implications for the mechanism of action of ribozymes. 169 23

Synthetic chocolate colourant, flavourant and the mixture of both were administered to healthy adult male albino rats to evaluate their effect on the nucleic acids metabolism, i.e. deoxyribonucleic and ribonucleic acids (DNA and RNA), total serum protein, thyroid hormones (T4 and T3) and nuclease enzymes, i.e. cytoplasmic- and mitochondrial deoxyribonuclease and ribonuclease (DNase and RNase) in brain, liver, and kidneys. Also, the activity of the fundamental enzymes of the oxidative pentose phosphate pathway, i.e. cytoplasmic and mitochondrial glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (G-6-PD and 6-PGD), as well as total lipids and cholesterol contents in the same organs were studied. Ingestion of the studied food additives significantly increased serum protein, RNA and T4 hormone, while, DNA and T3 hormone were insignificantly elevated. In connection with this, the hydrolytic enzymes of nucleic acids (DNase and RNase activities) were stimulated by all studied food additives and in all mentioned organs. The activity of G-6-PD and 6-PGD in both cytoplasmic and mitochondrial fractions of all studied organs were increased. The highest increase was noticed in rats fed on diets supplemented with the mixture of both colourant and flavourant followed by colourant then flavourant, respectively.
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PMID:Biochemical effect of chocolate colouring and flavouring like substances on thyroid function and protein biosynthesis. 171 48

When isolated human fibroblast lysosomes are incubated with 4 microM [32P]phosphate at pH 7.0, orthophosphate is transported into lysosomes and is rapidly incorporated into low and high molecular weight products. We have characterized the high molecular weight (HMW) lysosomal material into which [32P]phosphate is incorporated and have found it to consist of long chains of inorganic polyphosphate based on the following observations. 1) greater than 97% of HMW 32P-lysosomal material is converted to [32P]orthophosphate when incubated with 1 N HCl for 20 min at 100 degrees C. 2) Incubation of HMW 32P-lysosomal material at pH 7.0 and 65 degrees C for 96 h results in the formation of [32P]trimetaphosphate, which is known to be produced only from linear chains of polyphosphate under these conditions. 3) HMW 32P-lysosomal material is resistant to degradation by proteinase K, ribonuclease, and deoxyribonuclease and extracts into the aqueous phase during phenol/chloroform extractions. 4) HMW 32P-lysosomal material displays heterogeneous mobility on polyacrylamide gels with most chains ranging in length from 100 to at least 600 phosphate residues. 5) HMW 32P-lysosomal material is partially hydrolyzed under alkaline conditions to yield a continuous ladder of polyphosphate species differing by one or several residues in length on polyacrylamide gels.
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PMID:Incorporation of [32P]orthophosphate into long chains of inorganic polyphosphate within lysosomes of human fibroblasts. 174 Apr 14

The mechanism of action of ribonuclease (RNase) T1 is still a matter of considerable debate as the results of x-ray, 2-D nmr and site-directed mutagenesis studies disagree regarding the role of the catalytically important residues. Hence computer modelling studies were carried out by energy minimisation of the complexes of RNase T1 and some of its mutants (His40Ala, His40Lys, and Glu58Ala) with the substrate guanyl cytosine (GpC), and of native RNase T1 with the reaction intermediate guanosine 2',3'-cyclic phosphate (G greater than p). The puckering of the guanosine ribose moiety in the minimum energy conformer of the RNase T1-GpC (substrate) complex was found to be O4'-endo and not C3'-endo as in the RNase T1-3'-guanylic acid (inhibitor/product) complex. A possible scheme for the mechanism of action of RNase T1 has been proposed on the basis of the arrangement of the catalytically important amino acid residues His40, Glu58, Arg77, and His92 around the guanosine ribose and the phosphate moiety in the RNase T1-GpC and RNase T1-G greater than p complexes. In this scheme, Glu58 serves as the general base group and His92 as the general acid group in the transphosphorylation step. His40 may be essential for stabilising the negatively charged phosphate moiety in the enzyme-transition state complex.
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PMID:Computer modelling studies on the mechanism of action of ribonuclease T1. 174 59

The X-ray structures of two complexes of bovine ribonuclease-A produced by soaking pre-grown crystals in solutions of the inhibitors cytidylyl-2',5'-guanosine (2',5' CpG) and deoxycytidylyl-3',5'-guanosine (3',5'dCpdG) have been determined at 1.5 A resolution and refined by restrained least squares to R = 21.0% for 17,855 reflections, and R = 19.1% for 16,347 reflections, respectively. Binding of the substrate analogs to the protein has taken place in a completely unexpected and previously unreported manner. In each case the guanine base occupies the well characterized B1 pyrimidine binding site adjacent to Thr-45 (described by Richards, F.M., Wyckoff, H.W., Carlson, W.D., Allewell, N.M., Lee, B. and Mitsui, Y. (1971) Cold Spring Harbor Symp. Quant. Biol. 36, 35-54, and others including Palmer, R.A., Moss, D.S., Haneef, I. and Borkakoti, N. (1984) Biochim. Biophys. Acta 785, 81-88) having entered through a secondary channel external to the active site itself. We designate this reversed non-productive mode as retro-binding. In this mode of binding the SO4(2-) anion bound in the active site of the native protein crystals (Borkakoti, N., Moss, D.S. and Palmer, R.A. (1982) Acta Crystallogr. B38 2210-2217) has not been displaced by the phosphate of the inhibitor molecule as originally anticipated and observed in other studies. Instead the CMP or dCMP moiety of the inhibitor molecule is held loosely in a channel running towards the surface of the protein molecule and is thus completely external to the active site. Consequently, although it has been possible to model them, no attempt has been made to refine either the disordered cytosine in the CpG complex or the deoxycytosine in the dCpdG complex. The traditional B2 purine binding site of RNase (Richards et al., 1971) is unoccupied by the soaked inhibitors. Important changes that have taken place in the protein structure include: stabilization of both Lys-41 and Gln-11 via H-bonding to SO4(2-); stabilization of His-119 in the A conformation (Borkakoti, N., Moss, D.S. and Palmer, R.A. (1982) Acta Crystallogr. B38 2210-2217); and stabilization of SO4(2-) by H-bonds formed with the retro-bound guanine base. Binding of the inhibitors and stabilization of the active site is accompanied by displacement and redistribution of solvent molecules.
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PMID:Novel non-productively bound ribonuclease inhibitor complexes--high resolution X-ray refinement studies on the binding of RNase-A to cytidylyl-2',5'-guanosine (2',5'CpG) and deoxycytidylyl-3',5'-guanosine (3',5'dCpdG). 176 78

Two neutral ribonucleases have been purified from developing tomato fruit. Their activity is maximal 5 days after anthesis, declines during maturation, and then increases slightly in the mature green through breaker stages. The ribonucleases Tf1 and Tf2 have molecular weights of 59 and 29 K, respectively, based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and are glycoproteins. The reduced and denatured Tf1 is composed of two subunits, 30 and 29 K, of which only the 30-K subunit displays ribonuclease activity after renaturation. Reduced and denatured Tf2 is a single 29-K polypeptide that is renaturable to an active ribonuclease. Only the 30-K, active subunit of Tf1 is immunologically cross-reactive with Tf2. Both ribonucleases are cyclyzing endoribonucleases with a strong preference for cleavage at pyrimidine residues, thus generating oligonucleotide products ending with pyrimidine 2',3'-cyclic phosphate. These tomato fruit ribonucleases share a number of properties in common with the S-glycoprotein ribonucleases that are involved in self-incompatibility reactions in some solanaceous plants.
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PMID:Purification and characterization of two ribonucleases from developing tomato fruit. 192 99

Phosphate is a competitive inhibitor of transesterification of GpC by the ribonuclease barnase. Barnase is significantly stabilized in the presence of phosphate against urea denaturation. The data are consistent with the existence of a single phosphate binding site in barnase with a dissociation constant, Kd, of 1.3 mM. The 2D 1H NMR spectrum of wild-type barnase with bound phosphate is assigned. Changes in chemical shifts and NOEs for wild type with bound phosphate compared with free wild type indicate that phosphate binds in the active site and that only small conformational changes occur on binding. Site-directed mutagenesis of the active site residues His-102, Lys-27, and Arg-87 to Ala increases the magnitude of Kd for phosphate by more than 20-fold. The 2D 1H NMR spectra of the mutants His-102----Ala, Lys-27----Ala, and Arg-87----Ala are assigned. Comparison with the spectra of wild-type barnase reveals that His-102----Ala and Lys-27----Ala have essentially the same structure as weild type, while some structural changes occur in Arg-87----Ala. It appears that phosphate binding by barnase is effected mainly by positively charge residues including His-102, Lys-27, and Arg-87. This may have applications for the design of phosphate binding sites in other proteins.
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PMID:Characterization of phosphate binding in the active site of barnase by site-directed mutagenesis and NMR. 195 71


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