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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific beta-adrenergic receptors present in membrane preparations of frog erythrocytes were identified by binding of (-)-[3H]dihydroalprenolol, a potent competitive beta-adrenergic antagonist. The (-)-[3H]dihydroalprenolol binding sites could be solubilized by treatment of a purified erythrocyte membrane fraction with the plant glycoside digitonin but not by treatment with a wide variety of other detergents. The binding sites appeared to be soluble by several independent experimental criteria including (a) failure to sediment of 105,000 X g for 2 hours; (b) passage through 0.22-mu Millipore filters; (c) chromatography on Sepharose 6B gels; and (d) electron microscopy. The soluble receptor sites retained all of the essential characteristics of the membrane-bound sites, namely rapid and reversible binding of beta-adrenergic agonists and antagonists; strict stereospecificity toward both beta-adrenergic agonists and antagonists; appropriate structure-activity relationships; saturability of the sites at low concentrations of ligand; no affinity for alpha-adrenergic drugs, nonphysiologically active catechol compounds, and catecholamine metabolites. Based on gel chromatography in the presence of detergent, the molecular weight of the soluble receptor is estimated to be no greater than 130,000 to 150,000. Equilibrium binding studies indicated a KD for the soluble receptor of 2 nM. Hill coefficients (nH) of 0.77 and curved Scatchard plots suggested the presence of negatively cooperative interactions among the solubilized receptors in agreement with previous findings with the membrane-bound sites. Kinetic studies indicated an association rate constant K1 = 3.8 X 10(6) M-1 min-1 and a reverse rate constant k2 = 2.3 X 10(-3) min-1 at 4 degrees. The kinetically derived KD (k2/k1) of 0.6 nM is in reasonable agreement with that determined by equilibrium studies. The soluble receptors were labile at temperature greater than 4 degrees but could be stabilized with high concentrations of EDTA. Guanidine hydrochloride and urea produced concentration-dependent losses of binding activity which were partially reversible upon dialysis. Trypsin and phospholipase A both degraded the soluble receptors but a variety of other proteases and phospholipases as well as DNase and RNase were without effect. Experiments with group-specific reagents indicated that free lysine, tryptophan, serine, and sulfhydryl groups may be important for receptor binding. These studies suggest that the receptor is probably a protein which requires lipids for functional integrity. Data obtained with the solubilized binding sites are consistent with the contention that these sites represent the physiologically relevant beta-adrenergic receptors which have been extracted from the membranes with full retention of their properties.
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PMID:Solubilization and characterization of the beta-adrenergic receptor binding sites of frog erythrocytes. 0 47

1. Alkaline ribonuclease (pH optimum 7.6) was isolated from rye (Secale cereale L) germ cytosol and partially purified; the preparation was devoid of other nucleolytic activities. 2. The enzyme is a typical endonuclease hydrolysing all phosphodiester bonds in RNA, yielding ultimately purine and pyrimidine nucleoside 2',3'-cyclic phosphates and the corresponding 3'-phosphates. Upon extensive digestion of synthetic polyribonucleotides, pyrimidine, but not purine, nucleoside 3'-phosphates are formed. The enzyme does not hydrolyse synthetic purine cyclic nucleotides. 3. The enzyme does not depolymerize double-stranded complexes of poly(A) and poly(U). 4. Susceptibility to photooxidation and inhibition by 2-hydroxy-5-nitrobenzyl bromide and N-bromosuccinimide implies the involvement of tryptophan residue in the active centre of the enzyme.
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PMID:Alkaline ribonuclease from rye germ cytosol. 0 57

In order to investigate the nature of amino acid residues involved in the active in the active site of a ribonuclease from Aspergillus saitoi, the pH dependence of the rates of inactivation of RNase Ms by photooxidation and modification with diethylpyrocarbonate were studied. (1) RNase Ms was inactivated by illumination in the presence of methylene blue at various pH's. The pH dependence of the rate of photooxidative inactivation of RNase Ms indicated that at least one functional group having pKa 7.2 was involved in the active site. (2) Amino acid analyses of photooxidized RNase Ms at various stages of photooxidative inactivation at pH's 4.0 and 6.0 indicated that one histidine residue was related to the activity of RNase Ms, but that no tryptophan residue was involved in the active site. (3) 2',(3')-AMP prevented the photooxidative inactivation of RNase Ms. The results also indicated the presence of a histidine residue in the active site. (4) Modification of RNase Ms with diethylpyrocarbonate was studied at various pH's. The results indicated that a functional group having pKa 7.1 was involved in the active site of RNase Ms.
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PMID:Photooxidation and carbethoxylation of a minor ribonuclease from Aspergillus saitoi. 2 78

Smooth membranes have been isolated from a human diploid line of lymphocytes. These membranes exhibit an endogenous DNA-synthesizing capability which is partially destroyed by prior treatment with RNase. In order to ascertain the role of the membranes in the DNA synthesis we have examined the conformation of the membrane proteins by observing fluorescence changes of the intrinsic probe, tryptophan. We have observed that on addition of the deoxynucleoside-5'-triphosphates, which permits DNA synthesis, there are fluorescence changes due to the tryptophan residue; when DNA synthesis is prevented by omitting some of the precursor triphosphates, fluorescence changes are absent. These effects have been observed with plasma and nuclear membrane fractions; the former may contain a small fraction of the latter. Similar membrane preparations from non-lymphoid cells do not process the endogenous DNA-synthesizing system, as shown by the lack of incorporation of radioactive precursors of fluorescence changes.
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PMID:In vitro DNA synthesis on smooth membranes observed by fluorescence. 5 81

Tryptophanyl-tRNA was specifically labeled at the 3' end with [3H]tryptophan and cleaved in half with RNase under denaturing conditions, and the 3' half was shown to hybridize exclusively at the 5' end of avian myeloblastosis virus RNA. The RNA-dependent DNA polymerase of avian myeloblastosis virus is capable of efficiently binding the 3' half of the primer molecule.
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PMID:Primer recognition by avian myeloblastosis virus RNA-directed DNA polymerase. 6 28

Purified tRNATrp from bovine liver, accepting 1700 pmol tryptophan per A260nm unit, was completely digested with pancreatic ribonuclease and T1 ribonuclease. The sequences of the resulting oligonucleotides were determined and the primary structure of the tRNA was deduced. These analyses showed numerous incomplete post-transcriptional modifications, and several positions heterogenously occupied by two different nucleotides, which lead us to think that in bovine liver there exist a mixture of several tRNATrp.
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PMID:Primary structure of bovine liver tRNATrp. 10 55

Collagen-synthesizing polysomes were isolated by low-speed centrifugation of the post-mitochondrial supernatant of chick homogenates. Electron microscopy of the fraction thus isolated shows it to be exclusively composed of ribosomes. Amino acid incorporation in vitro showed that these particles were efficient in the incorporation of proline, but not tryptophan, as opposed to ribosomes obtained from the supernatant of the low-speed centrifugation. The incorporation process was highly dependent on GTP, and exibited an optimal Mg2+concentration of 5.6mM. The reaction was inhibited by RNase, elongation inhibitors as anysomycin, sparsomycin, fusidic acid and GDPCP. It was also moderately inhibited by initiation inhibitors such as aurintricarboxilic acid and pyrocatechol violet. The product of the incorporation was characterized as collagen by its sensitivity towards purified collagenase, lack of tryptophan, chromatography in CM-cellulose and molecular sieve chromatography in Sephadex G-200.
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PMID:Isolation and characterization of collagen-synthesizing polysomes from chick embryos. 16 69

This paper demonstrates the existence of regions in eight small globular proteins in which the side chains of sulfur-containing amino acids (cysteine and methionine) alternate in space with side chains of aromatic amino acids (histidine, phenylalanine, tryptophan and tyrosine). The proteins are: rubredoxin, high potential iron protein, cytochrome c, flavodoxin, deoxyhemoglobin, trypsin inhibitor, ribonuclease-S, and lysozyme. The sulfur-pi-bonded 'chains' involve a minimum of five and a maximum of 10 amino acids, and contain the most polarizable atoms within proteins. S-pi-chains give extra stability to the folding of proteins; they may also afford paths for the step-wise movement of electrons.
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PMID:Chains of alternating sulfur and pi-bonded atoms in eight small proteins. 20 19

From a strain of Escherichia coli with two copies of the tryptophan (trp) operon and one copy of the lactose (lac) operon, under control of one of the trp regulatory elements, we have isolated a mutant which does not grow in a medium containing 19 amino acids, unless tryptophan is added, and which cannot ferment lactose. The apparent pleiotropic nature of the mutation(s) is indicated by the very slow growth of mutant bacteria on minimal-medium agar supplemented with glucose and tryptophan. The amount of the trp enzymes (anthranilate synthetase and tryptophan synthetase) and trp messenger ribonucleic acid is reduced several-fold in the mutant compared to the isogenic wild-type strain, whereas the enzymes tryptophanyl-transfer ribonucleic acid synthetase and glucose 6-phosphate dehydrogenase remain the same. The incorporation of radioactive label into pulse-labeled but not into stable ribonucleic acid is significantly lower. Our results suggest that in the mutant organism the control of transcription of some operons, including the trp operon, is modified. An alternative explanation is that mutant bacteria contain a ribonuclease with increased activity for some messenger ribonucleic acid species.
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PMID:Escherichia coli mutant strain with altered expression of the tryptophan operon: isolation and preliminary characterization. 37 67

The second derivative absorption spectra of serum albumin, insulin, ribonuclease and lysozyme were measured under various conditions to determine the state and amount of their phenylalanine residues. The second derivative spectra of these proteins were very similar to that of phenylalanine in the region between 245 and 270 nm where tryptophan and tyrosine residues caused no appreciable interference. Denaturation of proteins with urea or guanidine hydrochloride caused decrease in the intensity of the second derivative spectra, but scarcely affected the positions of peaks and troughs. The amounts of phenylalanine residues in proteins calculated from a second derivative spectra of denatured proteins coincided well with those reported in the literature. The states of the phenylalanine residues in the proteins could be deduced from the change in optical intensity on denaturation.
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PMID:Estimation of state and amount of phenylalanine residues in proteins by second derivative spectrophotometry. 39 35


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