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

Helical regions in many tetrapyrrole proteins are highly amphiphilic, one side interacting with a hydrophobic core and another side interacting with the polar solvent. The mean helical hydrophobic moment is a measure of amphiphilicity of a helix. Helical regions in myoglobin, the alpha and beta subunits of C-phycocyanin, and cytochrome c can be distinguished from nonhelical regions by use of a hydrophobic moment analysis. 24 of 27 (89%) of the helical regions in these proteins were located by this analysis. Calculations were also performed on chymotrypsin, ribonuclease, and papain, which do not possess as pronounced a hydrophobic core as the tetrapyrrole-containing proteins. Less than 50% of the helical regions were correctly located, indicating a lack of amphiphilicity in the helices of these proteins. The hydrophobic moment analysis was also used to predict helical regions in phytochrome, the ubiquitous photoreceptor in plants. Additionally, this analysis is used to quickly locate internal hydrophilic residues which may be functionally important. The distribution of hydrophobic moments from a random sequence was determined so that qualitative and to some extent quantitative comparisons between different amphiphilic helices may be made.
...
PMID:Location of helical regions in tetrapyrrole-containing proteins by a helical hydrophobic moment analysis. Application to phytochrome. 217 Mar 85

The activity of purified bull seminal RNase was markedly stimulated by various basic proteins. At the half concentration of substrate RNA, basic proteins such as histones, high-mobility group chromosomal proteins and cytochrome c stimulated the enzyme activity 4-6 fold. Other non-basic proteins such as bovine serum albumin and human gamma-globulin were far less effective. In addition to enzyme-stimulating activity, basic proteins showed a marked enzyme-stabilizing activity, indicating the presence of a strong interaction between the enzyme and basic proteins.
...
PMID:Stimulation of bull seminal RNase by various basic proteins. 241 4

The attempt is made to find new correlations between local structural characteristics of proteins and the hydrogen exchange rates of their individual main-chain amides, and to relate such correlations to possible mechanisms of hydrogen exchange. It is found that in bovine pancreatic trypsin inhibitor (BPTI) the surface area buried by a particular residue and its neighbors correlates with the exchange rate of the main-chain amide of that residue. As the area buried by a particular fragment can be associated with the stabilization of the protein structure by this fragment, the correlation suggests a role for the energetics of the local unfolding in the mechanism of hydrogen exchange. Calculations based on the assumption that the exchange mechanism involves local unfolding lead to quantitative agreement between the calculated and experimentally measured exchange rates for 80% of the amides of BPTI that are buried or hydrogen bonded to the main-chain or to internal water molecules. The same degree of correlation is found between the calculated exchange rates and partial exchange data for ribonuclease S, hen lysozyme and cytochrome c. A similarly strong correlation is found between calculated exchange rates and the exchange rates of ribonuclease A determined by neutron diffraction in the crystal. The criteria of correlation are, however, less stringent in this case because of the experimental errors, which are larger than for solution data. It is suggested that the observed correlation be used for predictions of hydrogen exchange rates in proteins.
...
PMID:Correlation between calculated local stability and hydrogen exchange rates in proteins. 244 80

In the formation of covalent ubiquitin-protein conjugates that occurs during ATP- and ubiquitin-dependent proteolysis in reticulocyte extracts, ubiquitin (Ub) is activated to a thiol ester of the activating enzyme E1 (via the Ub carboxyl terminus), transferred to low-molecular weight "carrier proteins" (E2s) to form E2-Ub thiol esters, and then transferred by a third enzyme (E3) to amino groups on target proteins (Hershko, A., Heller, H., Elias, S., and Ciechanover, A. (1983) J. Biol. Chem. 258, 8206-8214). We report here the fractionation of Ub carrier proteins by molecular weight, and their characterization with respect to several activities. The Ub thiol ester forms of at least four of the five E2s catalyze Ub transfer to a number of small amines, in a reaction that does not require E3; only primary amines on primary carbons can serve as Ub acceptors. E3-independent Ub transfer to the small, basic proteins histones H2A and H2B, and cytochrome c, is also observed. The Ub thiol ester forms of two of the E2s were found to catalyze Ub transfer to cytochrome c. Only a single E2 functions in E3-dependent conjugate formation (with the substrates creatine phosphokinase, reduced/carboxymethylated serum albumin, and oxidized RNase) and in E3-dependent protein breakdown (with the substrate serum albumin). This E2 has a subunit molecular weight of 14,000 and migrates as a dimer on Sephacryl 200.
...
PMID:Functional heterogeneity of ubiquitin carrier proteins. 298 64

13C NMR spectroscopy has been used to characterize Amadori (ketoamine) adducts formed by reaction of [2-13C]glucose with free amino groups of protein. The spectra of glycated proteins were acquired in phosphate buffer at pH 7.4 and were interpreted by reference to the spectra of model compounds, N alpha-formyl-N epsilon-fructose-lysine and glycated poly-L-lysine (GlcPLL). The anomeric carbon region of the spectrum (approximately 90-105 ppm) of glycated cytochrome c was superimposable on that of N alpha-formyl-N epsilon-fructose-lysine, and contained three peaks characteristic of the alpha- and beta-furanose and beta-pyranose anomers of Amadori adducts to peripheral lysine residues on protein (pK alpha approximately 10.5). The spectrum of GlcPLL yielded six anomeric carbon resonances; the second set of three was displaced about 2 ppm to lower shielding of the first and was assigned to the Amadori adduct at the alpha-amino terminus (pK alpha approximately 7.5). The spectrum of glycated RNase was similar to that of GlcPLL, but contained a third set of three signals attributable to modification of active site lysine 41 (pK alpha approximately 8.8). The assignments for RNase were confirmed by analysis of spectra taken at pH 4 and under denaturing conditions. The spectrum of glycated hemoglobin was comparable to that of GlcPLL, and distinct resonances could be assigned to Amadori adducts at amino-terminal valine and intrachain N epsilon-lysine residues. Chemical analyses were performed to measure the relative extent of alpha- and epsilon-amino group modification in the glycated macromolecules, and the results were compared with estimates based on integration of the NMR spectra.
...
PMID:Characterization of glycated proteins by 13C NMR spectroscopy. Identification of specific sites of protein modification by glucose. 298 92

Galactosyltransferase (EC 2.4.1.22) requires bivalent metal ions for its activity. However, preparations of this enzyme solubilized from Golgi membranes of lactating rat mammary gland were shown to be activated not only by Mn2+, Ca2+ and Mg2+, but also by spermine, spermidine, lysyl-lysine, ethylenediamine and other diaminoalkanes, and by a range of basic proteins and peptides, including clupeine, histone, polylysine, ribonuclease, pancreatic trypsin inhibitor, cytochrome c, melittin, avidin and myelin basic protein. Both N-acetyl-lactosamine synthetase and lactose synthetase activities were enhanced. A basic protein fraction was isolated from bovine milk and shown to activate galactosyltransferase at low concentrations. The polyanions ATP, casein, chondroitin sulphate and heparin reversed the activation of galactosyltransferase by several of the above substances. Galactosyltransferase, assayed as a lactose synthetase, showed a 10-fold greater affinity for glucose when Mn2+ ions were replaced by clupeine or by ribonuclease as cationic activator. Evidence was obtained for the presence of an endogenous cationic activator in solubilized Golgi membrane preparations which evoked a similar low apparent Km,glucose. The findings are discussed in the light of cationic activations of glycosyltransferases generally, of the porous nature of the Golgi membrane, and of the unlikelihood of bivalent metal ions being the physiological activators of galactosyltransferase. It is suggested that the natural cationic activator of lactose synthetase may be a secretory protein acting in a manner analogous to the enzyme's activation by alpha-lactalbumin. A scheme is proposed for the two-stage synthesis of lactose and phosphorylation of casein within the cell, to accommodate the apparent incompatibility of these two processes.
...
PMID:Cationic activation of galactosyltransferase from rat mammary Golgi membranes by polyamines and by basic peptides and proteins. 310 66

With the synthesis of a new, strongly basic Immobiline (pK 10.3 at 10 degrees C) it has been possible to formulate a new pH 10-11 recipe for focusing very alkaline proteins, not amenable to fractionation with conventional isoelectric focusing in carrier ampholyte buffers. In this formulation, water is added as an acidic Immobiline having pK = 14 and a unit molar concentration (or with a pK = 15.74 and standard 55.56 molarity) since around pH 11 its buffering power becomes significant. The gel contains a 'conductivity quencher', i.e. a density gradient incorporated in the matrix, with the dense region located on the cathodic side (pH 11) for (a) smoothing the voltage gradient on the separation cell and (b) reducing the anodic electrosmotic flow due to the net positive charge acquired by the matrix at pH 11 (1 mM excess protonated amino groups to act as counterions to the 1 mm OH- groups in the bulk water solution generated by the local value of pH 11). Excellent focusing is obtained for such alkaline proteins as lysozyme (pI 10.55), So-6 (a leaf protein, pI 10.49), cytochrome c (pI 10.45) and ribonuclease (pI 10.12).
...
PMID:Isoelectric focusing in immobilized pH gradients in the pH 10-11 range. 342 69

The glycation (nonenzymatic glycosylation) of several proteins was studied in various buffers in order to assess the effects of buffering ions on the kinetics and specificity of glycation of protein. Incubation of RNase with glucose in phosphate buffer resulted in inactivation of the enzyme because of preferential modification of lysine residues in or near the active site. In contrast, in the cationic buffers, 3-(N-morpholino)propane-sulfonic acid and 3-(N-tris(hydroxymethyl)methyl-amino)-2-hydroxypropanesulfonic acid, the kinetics of glycation of RNase were decreased 2- to 3-fold, there was a decrease in glycation of active site versus peripheral lysines, and the enzyme was resistant to inactivation by glucose. The extent of Schiff base formation on RNAse was comparable in the three buffers, suggesting that phosphate, bound in the active site of RNase, catalyzed the Amadori rearrangement at active site lysines, leading to the enhanced rate of inactivation of the enzyme. Phosphate catalysis of glycation was concentration-dependent and could be mimicked by arsenate. Phosphate also stimulated the rate of glycation of other proteins, such as lysozyme, cytochrome c, albumin, and hemoglobin. As with RNase, phosphate affected the specificity of glycation of hemoglobin, resulting in increased glycation of amino-terminal valine versus intrachain lysine residues. 2,3-Diphosphoglycerate exerted similar effects on the glycation of hemoglobin, suggesting that inorganic and organic phosphates may play an important role in determining the kinetics and specificity of glycation of hemoglobin in the red cell. Overall, these studies establish that buffering ions or ligands can exert significant effects on the kinetics and specificity of glycation of proteins.
...
PMID:Effect of phosphate on the kinetics and specificity of glycation of protein. 358 12

Bovine pancreatic ribonuclease (RNase) A and S protein (enzymatically inactive proteolytic fragment of RNase A which contains RNA binding site) stimulate the activation, as evidenced by increasing DNA-cellulose binding, of highly purified rat hepatic glucocorticoid-receptor complexes. These effects are dose dependent with maximal stimulation of DNA-cellulose binding being detected at approximately 500 micrograms (50 units of RNase A/mL). RNase A and S protein do not enhance DNA-cellulose binding via their ability to interact directly with DNA or to increase nonspecific binding of receptors to cellulose. Neither S peptide (enzymatically inactive proteolytic fragment which lacks RNA binding site) nor cytochrome c, a nonspecific basic DNA binding protein, mimics these effects. RNase A and S protein do not stimulate the conformational change which is associated with activation and is reflected in a shift in the elution profile of receptor complexes from DEAE-cellulose. In contrast, these two proteins interact with previously heat-activated receptor complexes to further enhance their DNA-cellulose binding capacity and thus mimic the effects of an endogenous heat-stable cytoplasmic protein(s) which also function(s) during step 2 of in vitro activation [Schmidt, T. J., Miller-Diener, A., Webb, M. L., & Litwack, G. (1985) J. Biol. Chem. 260, 16255-16262]. Preadsorption of RNase A and S protein to an RNase affinity resin containing an inhibitory RNA analogue, or trypsin digestion of the RNA binding site within S protein, eliminates the subsequent ability of these two proteins to stimulate DNA-cellulose binding of the purified receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Effects of bovine pancreatic ribonuclease A, S protein, and S peptide on activation of purified rat hepatic glucocorticoid-receptor complexes. 379 Apr 97

Yeast cells, Candida utilis, in water suspension and in the absence of electrolytes were found to be very sensitive to several proteins of moderate size, including ribonuclease, protamine, lysozyme, bovine serum albumin, cytochrome c, and myoglobin. Viability ceases rapidly, and ultraviolet-absorbing compounds (260 mmu) and the amino acid pool are released into the medium. The ultraviolet-absorbing material appears to be the nucleotide and coenzyme fraction usually extracted by 0.2 n perchloric acid at low temperature. The ribonucleic acid fraction remains in the cell ghosts and can be released by ribonuclease. The enzymatic properties of some of these proteins have no relation to their damaging effect on the cell membrane. Poly-l-lysine shows the same activity.
...
PMID:Effect of some proteins on the yeast cell membrane. 429 20


<< Previous 1 2 3 4 5 6 7 Next >>

---