Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of electrostatics in the adsorption process of proteins to preformed negatively-charged (phosphatidylcholine/phosphatidylglycerol) and neutral (phosphatidylcholine) liposomes was studied. The interaction was monitored at low ionic strength for a set of model proteins as a function of pH. The adsorption behavior of trypsin inhibitor (pI = 4.6), myoglobin (pI = 7.4), ribonuclease (pI = 9.6), and lysozyme (pI = 10.7) with preformed liposomes was investigated, along with changes in the electrophoretic mobility of liposomes through the adsorption of charged proteins. Mean protein charge was determined by acid/base titration. Significant adsorption of the proteins to negatively-charged liposomes was only found at pH values where the number of positive charge moieties exceeds the number of negative charge moieties on the protein by at least three charge units. Negligible adsorption to liposomes composed of zwitterionic lipids was observed in the pH range tested (4-9). The absolute value of the electrophoretic mobilities of negatively-charged, empty liposomes decreased after adsorption of positively-charged proteins. With increasing protein to phospholipid ratio, the drop in the electrophoretic mobility leveled off and reached a plateau; protein adsorption profiles showed a similar shape. Analysis of the data demonstrated that neutralization of the liposome charge due to the adsorption of the positively-charged proteins is the controlling factor in their adsorption. The plateau level reached depended on the type of protein and the pH of the incubation medium. This pH dependency could be ascribed to the mean positive charge of the protein.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The role of protein charge in protein-lipid interactions. pH-dependent changes of the electrophoretic mobility of liposomes through adsorption of water-soluble, globular proteins. 848 42

The folding assistant and chaperone protein-disulfide isomerase (PDI) catalyzes disulfide formation, reduction, and isomerization of misfolded proteins. PDI substrates are not restricted to misfolded proteins; PDI catalyzes the dithiothreitol (DTT)-dependent reduction of native ribonuclease A, microbial ribonuclease, and pancreatic trypsin inhibitor, suggesting that an ongoing surveillance by PDI can test even native disulfides for their ability to rearrange. The mechanism of reduction is consistent with an equilibrium unfolding of the substrate, attack by the nucleophilic cysteine of PDI followed by direct attack of DTT on a covalent intermediate between PDI and the substrate. For native proteins, the rate constants for PDI-catalyzed reduction correlate very well with the rate constants for uncatalyzed reduction by DTT. However, the rate is weakly correlated with disulfide stability, surface exposure, or local disorder in the crystal. Compared with native proteins, scrambled ribonuclease is a much better substrate for PDI than predicted from its reactivity with DTT; however, partially reduced bovine pancreatic trypsin inhibitor (des(14-38)) is not. An extensively unfolded polypeptide may be required by PDI to distinguish native from non-native disulfides.
 ...
PMID:Discrimination between native and non-native disulfides by protein-disulfide isomerase. 1127 5

A protease designated pleureryn, with an N-terminal sequence dissimilar from previously reported mushroom metalloendopeptidases and showing only limited resemblance to aspartic proteinases, albeit considerable homology to DNA replication licensing factor, was isolated from fresh fruiting bodies of the edible mushroom Pleurotus eryngii. The purification protocol entailed ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel Blue gel, ion exchange chromatography on CM-Sepharose, and FPLC-gel filtration on Superdex 75. The protease was unadsorbed on DEAE-cellulose but adsorbed on Affi-gel Blue gel and CM-Sepharose. It demonstrated a single band with a molecular weight of 11.5 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Pleureryn demonstrated a protease activity of 9364 U/mg toward casein. It exhibited a pH optimum of 5.0 and a temperature optimum of 45 degrees C, with substantial activity remaining at high temperatures and pH 4 and 12. The activity of the protease was adversely affected by pepstatin A, indicating that it is an aspartic protease. PMSF, trypsin inhibitor, and EDTA exerted no striking effect, suggesting that it is neither a serine protease nor a metalloprotease. It inhibited translation in a rabbit reticulocyte lysate system with an IC(50) of 20 nM. Pleureryn also exhibited some inhibitory activity against HIV-1 reverse transcriptase, reminiscent of a suppressive action of HIV-1 protease on its homologous reverse transcriptase but was devoid of ribonuclease, deoxyribonuclease, and antifungal activities.
 ...
PMID:Pleureryn, a novel protease from fresh fruiting bodies of the edible mushroom Pleurotus eryngii. 1172 12

Napins are 1:1 disulfide-linked complexes of a smaller (ca. 4kDa) subunit and a larger (ca. 10kDa) subunit. The intent of the present study was to ascertain the production of napin by the seeds of a Brassica species that has not been examined previously, and also to explore new biological activities of the napin. A heterodimeric 11-kDa napin-like polypeptide has been isolated from Chinese white cabbage (Brassica chinensis cv dwarf) seeds with a protocol comprising ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, fast protein liquid chromatography (FPLC)-ion exchange chromatography on Mono S and FPLC-gel filtration on Superdex 75. The N-terminal sequence of the 7-kDa subunit manifests striking similarity to napin large chain, albumin and trypsin inhibitor. The N-terminal sequence of the 4-kDa subunit is homologous to napin large chain and an antimicrobial peptide. The napin-like polypeptide inhibited translation in the rabbit reticulocyte system with an IC50 of 18.5nM. This translation-inhibitory activity was stable between pH 4 and 11, and between 10 and 40 degrees C. The polypeptide inhibited trypsin with a higher potency ( IC50 = 8.5 microM) than it inhibited chymotrypsin (IC50 = 220 microM), but was devoid of ribonuclease and antifungal activities. It manifested antibacterial activity against Pseudomonas aeruginosia, Bacillus subtilis, Bacillus cereus, and Bacillus megaterium. The results revealed that the napin-like polypeptide from Chinese white cabbage seeds exhibited some potentially exploitable activities.
 ...
PMID:A napin-like polypeptide from dwarf Chinese white cabbage seeds with translation-inhibitory, trypsin-inhibitory, and antibacterial activities. 1506 97

Transglutaminases (TGs) are known to exhibit remarkable specificities not only for the Q (or Gln) sites but also for the K (or Lys) sites of proteins with which they react. To gain further insight into K-site specificity, we examined the reactions of dansyl-epsilon-aminocaproyl-GlnGlnIleVal with three chemically and structurally well-characterized proteins (bovine pancreatic ribonuclease A, bovine pancreatic trypsin inhibitor, and chicken egg white lysozyme), as catalyzed by TG2, a biologically important post-translational enzyme. The substrates represent a total of 20 potential surface sites for acylation by the fluorescent Gln probe, yet only two of the lysine side chains reacted with TG2. While the K1 site of ribonuclease and the K15 site of the trypsin inhibitor could be readily acylated by the enzyme, none of the lysines in lysozyme were modified. The findings lead us to suggest that the selection of lysine residues by TG2 is not encoded in the primary amino acid sequence surrounding the target side chain but depends primarily on its being positioned in an accessible segment of the protein structure.
 ...
PMID:Selectivity in the post-translational, transglutaminase-dependent acylation of lysine residues. 1922 23

A large number of trypsin inhibitors belonging to various types have been purified from different kinds of legumes. In this study, by using liquid chromatography, a Kunitz type trypsin inhibitor (KBTI) with a molecular weight of 20107.645 Da was purified from Korean large black soybeans. KBTI reduced the proteolytic activities of trypsin and alpha-chymotrypsin with the activity of approximately 8520 BAEE units/mg and approximately 24 BTEE units/mg, respectively. It showed high thermal stability (0-100 degrees C) as well as stability over a large range of pH values (pH 3-11). Furthermore, KBTI inhibited HIV-1 reverse transcriptase activity with an IC(50) value of 0.71 microM and induced the release of pro-inflammatory cytokines such as TNF-alpha, IL-1beta, IL-2 and interferon-gamma at the mRNA level. KBTI exerted weak antiproliferative activity toward CNE-2 and HNE-2 nasopharyngeal cancer cells, MCF-7 breast cancer cells, and Hep G2 hepatoma cells. KBTI was destitute of mitogenic, ribonuclease and antifungal activities.
 ...
PMID:Thermostable Kunitz trypsin inhibitor with cytokine inducing, antitumor and HIV-1 reverse transcriptase inhibitory activities from Korean large black soybeans. 2015 65

In this paper, the effect of temperature is investigated on the performance of glycoprotein enrichment by boronic acid lectin affinity chromatography (BLAC). Wheat germ agglutinin and m-aminophenyl boronic acid containing stationary phases were evaluated individually and in a mixed mode using an automated liquid handling robot with an integrated 96-well plate temperature controller. Glycoaffinity enrichment of the model proteins of ribonuclease B and trypsin inhibitor was investigated in the presence of the non-glycosylated proteins of myoglobin (neutral) and lysozyme (basic) at a wide temperature range of 5-65 degrees C. Our results revealed that glycoaffinity micropartitioning at the temperature of 25 degrees C provided the highest recovery rate for glycoprotein enrichment. We have also found that a large amount of lysozyme was present in the elution fractions of the m-aminophenyl boronic acid containing micropartitioning columns due to ion-exchange mechanism occurring between the positively charged protein and the negatively charged stationary phase at the operation pH. On the other hand, at high temperature (65 degrees C), non-specific interactions with the agarose carrier prevailed, evidenced by the presence of myoglobin in the eluate.
 ...
PMID:Boronic acid lectin affinity chromatography (BLAC). 3. Temperature dependence of glycoprotein isolation and enrichment. 2049 Apr 66


<< Previous 1 2 3