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

Four, widely used, ribonucleases were found to protect their substrates from acid precipitation by causing, evidently, a modification of their physicochemical properties. The protection was dependent on the kind of substrate while the ratio of protective to nucleolytic activity varied widely between the four enzymes. The protection was enhanced by some nucleotides like UMP, CMP and IMP and decreased in the presence of several bivalent ions like Zn++, Co++ and Cu++. It was completely abolished when the substrates were hybridized with their complementary ribohomopolymers. In the case of bovine pancreatic ribonuclease, the part of the molecule which was responsible for the protective activity was localized on the enzyme domain characterized as S-protein, which lacks nucleolytic activity. The observed property of ribonucleases could lead to false data when the measurement of TCA-soluble material is the method used to follow the purification of ribonucleases or to study their activity. It was also found that ribonuclease S-protein enhances the catalytic activity of B. Cereus RNAse. S-protein could potentiate other RNAses activity like onconase, which has recently been used as an anticancer agent.
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PMID:Ribonucleases protect RNA from acid precipitation. 948 43

Profiles of nucleotide levels in two varieties of Japanese green teas (cv. Yabukita and Saemidori), a Chinese green tea (Longjing), and two Japanese black teas (cv. Benifuuki and Benihikari) were determined and compared with that of fresh tea leaves. The concentration of 5'-nucleotides in green tea was much higher than in black tea. Nucleoside diphosphates were present in larger amounts than nucleoside triphosphates in manufactured green and black teas, whereas the triphosphates predominated in fresh tea leaves. Low levels of 3'-nucleotides were found in green and black teas. Inosine 5'-monophosphate, which is utilized as a seasoning component, was found in all manufactured teas in concentrations ranging from 50 to 200 nmol/g of dry weight. The levels of both inosine 5'-monophosphate and guanosine 5'-monophosphate were high in Chinese Longjing green tea. The unique profiles of nucleotides in manufactured teas may be a consequence of the action of degradation enzymes, such as ribonuclease, apyrase, phosphatase, nucleotidase, and adenosine 5'-monophsphate deaminase during the commercial processing of the young leaves.
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PMID:Profiles of purine and pyrimidine nucleotides in fresh and manufactured tea leaves. 1155 41

Proteins interact with nucleotides to perform a multitude of functions within cells. These interactions are highly specific; however, the molecular basis for this specificity is not well understood. To identify factors critical for protein-guanine nucleotide recognition the binding of two closely related ligands, guanosine 3'-monophosphate (3'GMP) and inosine 3'-monophosphate (3'IMP), to Ribonuclease Sa (RNase Sa), a small, guanylyl-endoribonuclease from Streptomyces aureofaciens, was compared using isothermal titration calorimetry, NMR, X-ray crystallography and molecular dynamics simulations. This comparison has allowed for the determination of the contribution of the exocyclic amino group "N2" of the guanine base to nucleotide binding specificity. Calorimetric measurements indicate that RNase Sa has a higher affinity for 3'GMP (K=(1.5+/-0.2)x10(5)) over 3'IMP (K=(3.1+/-0.2)x10(4)) emphasizing the importance of N2 as a key determinant of RNase Sa guanine binding specificity. This result was unexpected as the published structural data for RNase Sa in complex with 3'GMP showed only a potential long-range interaction (>3.3A) between N2 and the side-chain of Glu41 of RNase Sa. The observed difference in affinity is largely due to a reduction in the favorable enthalpy change by 10 kJ/mol for 3'IMP binding as compared to 3'GMP that is accompanied by a significant difference in the heat capacity changes observed for binding the two ligands. To aid interpretation of the calorimetric data, the first crystal structure of a small, guanylyl ribonuclease bound to 3'IMP was determined to 2.0 A resolution. This structure has revealed small yet unexpected changes in the ligand conformation and differences in the conformations of the side-chains contacting the sugar and phosphate moieties as compared to the 3'GMP complex. The structural data suggest the less favorable enthalpy change is due to an overall lengthening of the contacts between RNase Sa and 3'IMP as compared to 3'GMP. The long-range interaction between N2 and Glu41 is critical for positioning of the nucleotide in the binding cleft for optimal contact formation. Thus, combined, the data demonstrate how a long-range interaction can have a significant impact on nucleotide binding affinity and energetics.
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PMID:Molecular basis for nucleotide-binding specificity: role of the exocyclic amino group "N2" in recognition by a guanylyl-ribonuclease. 1630 Jul 86