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)

A variety of proteins have been studied for their ability to interact and alter the thermotropic properties of phospholipid bilayer membranes as detected by differential scanning calorimeter. The proteins studied included: basic myelin protein (A1 protein), cytochrome c, major apoprotein of myelin proteolipid (N-2 apoprotein), gramicidin A, polylysine, ribonuclease and hemoglobin. The lipids used for the interactions were dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol. The interactions were grouped in three catagories each having very different effects on the phospholipid phase transition from solid to liquid crystalline. The calorimetric studies were also correlated with data from vesicle permeability and monolayer expansion. Ribonuclease and polylysine which exemplify group 1 interactions, show strong dependence on electrostatic binding. Their effects on lipid bilayers include an increase in the enthalpy of transition (deltaH) accompanied by either an increase or no change in the temperature of transition (Tc). In addition, they show minimal effects on vesicle permeability and monolayer expansion. It was concluded that these interactions represent simple surface binding of the protein on the lipid bilayer without penetration into the hydrocarbon region. Cytochrome c and A1 protein, which exemplify group 2 interactions, also show a strong dependence on the presence of net negative charges on the lipid bilayers for their binding. In contrast to the first group, however, they induce a drastic decrease in both Tc and deltaH of the lipid phase transition. Furthermore, they induce a large increase in the permeability of vesicles and a substantial expansion in area of closely packed monolayers at the air-water interface. It was concluded that group 2 interactions represent surface binding followed by partial penetration and/or deformation of the bilayer. Group 3 interactions, shown by proteolipid apoprotein and gramicidin A, were primarily non-polar in character, not requiring electrostatic charges and not inhibited by salt and pH changes. They had no appreciable effect on the Tc but did induce a linear decrease in the magnitude of the deltaH, proportional to the percentage of protein by weight. Membranes containing 50% proteolipid protein still exhibited a thermotropic transition with a deltaH one half that of the pure lipid, and only a small diminution of the size of the cooperative unit. It was concluded that in this case the protein was embedded within the bilayer, associating with a limited number of molecules via non-polar interactions, while the rest of the bilayer was largely unperturbed.
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PMID:Effects of proteins on thermotropic phase transitions of phospholipid membranes. 5 74

The distribution of ribonucleoprotein (RNP) within the mitotic spindle of newt lung epithelial cells was studied with the high voltage electron microscope (HVEM) using Bernhard's uranyl-EDTA-lead staining of thick sections in conjunction with the ribonuclease digestion of fixed cells. The results indicate that aside from ribosomes, the major RNP-containing components of the spindle are the kinetochores and centrioles, both of which stain electron-opaque after EDTA treatment. In both cases, the electron-opaque material associated with these microtubule organizing centers (MTOC's) can be removed by RNAse digestion and cold perchloric acid (PCA) extraction under conditions which leave the spindle microtubules (Mts) centrioles, and kinetochores intact. The staining reaction is not abolished by cold PCA extraction alone or by substituting other positively charged proteins (i.e., cytochrome c or lysozyme) for RNAse. The RNP component of the kinetochore is closely associated with the bases of the kinetochore microtubules. The RNP component of the centriole can be seen to surround the microtubules of the triplet blades. No evidence was found to indicate the presence of RNP in the pericentriolar material. The possible function of both kinetochore and centriolar RNP is discussed.
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PMID:Ribonucleoprotein staining of centrioles and kinetochores in newt lung cell spindles. 8 14

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

The in vitro folding kinetics of a fragment corresponding to an intact dimer of the Cgamma3 domain of human IgG1 (pFc') were monitored via the large changes in tryptophan fluorescence which accompany these processes. In going from the guanidine hydrochloride (Gdn.HCl) induced unfolded state (4.0 M Gdn.HCl) to the native state (0.5 M Gdn.HCl), three well-separated first-order processes were observed having time constants of 5, 50, and 350 s and roughly equal amplitudes. These values were concentration independent, a fact consistent with there being no fluorescence change accompanying dimerization. These time constants are one to two orders of magnitude slower than those observed for proteins of similar size such as ribonuclease or cytochrome c, most probably reflecting the complex processes involved in forming the correct beta-sheet arrangement of immunoglobulin domains. The corresponding unfolding transition is biphasic having time constant values of 50 and 500 s, the latter comprising 80% of the fluorescence change. These data indicate the presence of at least one species with intermediate fluorescence along the unfolding pathway. Gdn.HCl concentration jumps were also performed over various intervals within the transition zone. The results are not consistent with a fully reversible mechanism. In the absence of the intrachain disulfide bond, pFc' exists in an unfolded state even at 0.5 M Gdn.HCl. In a concomitant refolding and reoxidation experiment (at 0.5 M Gdn.HCl and using an optimal disulfide interchange catalytic system), the time constant for disulfide formation was in the range of 80--200 s and the fluorescence change revealed a lag phase analyzable in terms of rate-limiting reoxidation and refolding times consistent with those observed for the initially disulfide bonded species. Under similar conditions but a 4 M Gdn.HCl, reoxidation was more than two orders of magnitude slower, suggesting that reoxidation is directed by a refolding nucleation event.
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PMID:Folding pathways of immunoglobulin domains. The folding kinetics of the Cgamma3 domain of human IgG1. 46 72

Under defined conditions, in the presence of 10 mg/ml of bovine serum albumin, cauda epididymal rat spermatozoa displayed vigorous motility, and a high proportion (81%) of eggs were fertilized. In contrast, no fertilization was observed after omission of albumin, or replacement of the protein by 10 mg/ml of cytochrome c, beta-globulin, gamma-globulin, hemoglobin, lysozyme, and polyvinylpyrrolidone, and 5 mg/ml of ribonuclease. However, high motility occurred in suspensions containing 3 x 10(6) spermatozoa/0.1 ml of medium with cytochrome c, beta-globulin, or gamma-globulin. In medium with 1 mg/ml of ovalbumin, 7% (2/29) eggs were fertilized. Use of defatted albumin resulted in a higher rate of fertilization than unmodified albumin (87 vs 70%), and this difference approached statistical significance. No fertilization was obtained in the presence of albumin presaturated with cholesterol. These results suggest that: (a) rat sperm cells failed to capacitate in the absence of albumin; (b) the protein exerted more than a nonspecific macromolecular effect; and (c) lipids associated with albumin may modify its ability to promote sperm capacitation.
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PMID:Influence of serum albumin on the fertilizing ability in vitro of rat spermatozoa. 125 Aug 65

The formation of hydrogen-bonded structure in the folding reaction of ubiquitin, a small cytoplasmic protein with an extended beta-sheet and an alpha-helix surrounding a pronounced hydrophobic core, has been investigated by hydrogen-deuterium exchange labeling in conjunction with rapid mixing methods and two-dimensional NMR analysis. The time course of protection from exchange has been measured for 26 back-bone amide protons that form stable hydrogen bonds upon refolding and exchange slowly under native conditions. Amide protons in the beta-sheet and the alpha-helix, as well as protons involved in hydrogen bonds at the helix/sheet interface, become 80% protected in an initial 8-ms folding phase, indicating that the two elements of secondary structure form and associate in a common cooperative folding event. Somewhat slower protection rates for residues 59, 61, and 69 provide evidence for the subsequent stabilization of a surface loop. Most probes also exhibit two minor phases with time constants of about 100 ms and 10 s. Only two of the observed residues, Gln-41 and Arg-42, display significant slow folding phases, with amplitudes of 37% and 22%, respectively, which can be attributed to native-like folding intermediates containing cis peptide bonds for Pro-37 and/or Pro-38. Compared with other proteins studied by pulse labeling, including cytochrome c, ribonuclease, and barnase, the initial formation of hydrogen-bonded structure in ubiquitin occurs at a more rapid rate and slow-folding species are less prominent.
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PMID:Early hydrogen-bonding events in the folding reaction of ubiquitin. 131 11

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

Reactions of MDA with primary amino groups produce inter- or intra-molecular 1-amino-3-imino-propene (AIP) bridges, leading to structural modifications of biological molecules. In this work, applying electrophoresis followed by transfer onto nitrocellulose membranes, we observed that serum of a rabbit immunized with MDA-modified lysozyme (ML) reacts not only with ML and native lysozyme (L), but also with MDA-modified ribonuclease, cytochrome c or polylysine (MR, MC and MP respectively), while it does not react with native ribonuclease, cytochrome c or polylysine (R, C and P respectively). These results confirm previous ones indicating that sera of rabbits immunized with ML contain antibodies reacting specifically with epitopes containing AIP bridges.
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PMID:Immunological relevance of malonic dialdehyde (MDA): IV. Further evidences about the epitope recognized by antibodies obtained from rabbits immunized with MDA-modified lysozyme. 172 67

Although there has been much speculation on the pathways of protein folding, only recently have experimental data on the topic been available. The study of proteins under conditions where species intermediate between the fully folded and unfolded states are stable has provided important information, for example about the disulphide intermediates in BPTI, cis/trans proline isomers of RNase A3 and the molten globule state of alpha-lactalbumin. An alternative approach to investigating folding pathways has involved detection and characterization of transient conformers in refolding studies using stopped-flow methods coupled with NMR measurements of hydrogen exchange. The formation of intermediate structures has been detected in the early stages of folding of cytochrome c, RNaseA and barnase. For alpha-lactalbumin, hydrogen exchange kinetics monitored by NMR proved to be crucial for identifying native-like structural features in the stable molten globule state. An analogous partially folded protein stable under equilibrium conditions has not been observed for the structurally homologous protein hen egg-white lysozyme, although there is evidence that a similar but transient state is formed during refolding. Here we describe NMR experiments based on competition between hydrogen exchange and the refolding process which not only support the existence of such a transient species for lysozyme, but enable its structural characteristics to be defined. The results indicate that the two structural domains of lysozyme are distinct folding domains, in that they differ significantly in the extent to which compact, probably native-like, structure is present in the early stages of folding.
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PMID:Demonstration by NMR of folding domains in lysozyme. 200 Jan 38

Alloreactive T cell hybridomas specific for IEk and/or IEb MHC Ag were obtained from IE-nonexpressor (IE alpha b) mice. The TCR V alpha and V beta gene segments used were identified by Northern blot and RNase protection. A large proportion (24 of 80 hybridomas tested) employed the same V alpha genes (V alpha 11.1 or V alpha 11.2) as are utilized in the IEk and IEb restricted response to the Ag cytochrome c. Of these 24 alloreactive hybridomas, 10 also expressed V beta genes utilized in the IE plus cytochrome c repertoire. Structural similarity between the two related sets of TCR indicates that V alpha segments can play a determining role in MHC specificity. These data also suggest that thymic selection based on TCR reactivity with self-MHC products acts on particular V(D)J combinations rather than on V alpha V beta pairings alone.
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PMID:Expression of identical V alpha V beta gene pairs by IE-alloreactive and IE-restricted, antigen-specific T cells from MHC disparate mice. Evidence for thymic selection of V(D)J combinations. 215 68


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