Studies on extracellular ribonucleases of Ustilago sphaerogena. Characterization of substrate specificity with special reference to purine-specific ribonucleases

The nucleotide sequence at the 5'-terminus of the Q RNA minus trand

The sequence of the first 52 nucleotides at the 5'-end of the Qbeta minus strand has been determined and found to be complementary in an antiparallel fashion to the 3'-terminal region of the Qbeta plus strand. There are few similarities between the corresponding sequences of Qbeta plus and minus strands; however, both have a hydrogen-bonded loop close to the 5'-end. The sequence of the 3'-terminal region of the plus strand was deduced: there are no termination signals within the last 32 nucleotides. A notable homology exists between the 3'-ends of Qbeta and R17 RNA.

Specificity of ribonuclease Ch from Chalaropsis species

A ribonuclease is produced by the fungus Chalaropsis sp. that appears to have an absolute specificity for 3'-guanylic acid residues in ribonucleic acid.

Serum copper alteration after ingestion of an oral contraceptive

Changes in the concentration of copper in the serum after administration of an oral contraceptive were determined with atomic absorption spectrophotometry. Statistically significant (P = .001) increases were observed in all volunteers.

Studies on extracellular ribonucleases of Ustilago sphaerogena. Purification and properties

1. Four ribonucleases were isolated from culture media of Ustilago sphaerogena. They were designated ribonucleases U(1), U(2), U(3) and U(4). 2. They were purified about 1600-, 3700-, 1100- and 16-fold respectively. 3. It was shown by gel filtration that ribonucleases U(1), U(2) and U(3) have molecular weights about 10000 like ribonuclease T(1), and that ribonuclease U(4) is much larger. 4. Ribonucleases U(1), U(2) and U(3) are thermostable, but ribonuclease U(4) is not. 5. The pH optimum of ribonucleases U(1) and U(4) is pH8.0-8.5, and that of ribonucleases U(2) and U(3) is pH4.5.