A cross-linked dimer of pancreatic ribonuclease A (ribonucleate 3'-pyrimidino-olitonucleotidohydrolase, EC 3.1.4.22), at a 10 mg/liter concentration, blocks proliferation of tumor cells. The protein retains this ability after inactivation by iodoacetate. The cytostatic effect of ribonuclease preparations on various cell lines correlates well with their rate of uptake: for example, monomeric rib...

Ribonuclease A and ribonuclease S-protein have been investigated for their ability to catalyze the preparative synthesis of dinucleoside monophosphates and trinucleoside diphosphates of specific base composition and sequence. Kinetic analysis of identical reactions catalyzed by ribonuclease A and S-protein suggests that the synthetic activity of the native protein and the derivative differ with...

Ribonuclease (RNase) Sa3 is secreted by the Gram-positive bacterium Streptomyces aureofaciens. The enzyme catalyzes the cleavage of RNA on the 3' side of guanosine residues. Here, x-ray diffraction analysis was used to determine the three-dimensional structure of two distinct crystalline forms of RNase Sa3 to a resolution of 2.0 and 1.7 A. These two structures are similar to each other as well ...

Homogenates of leaflets of desiccated tomato plants show increased ribonuclease activity compared to homogenates of turgid controls. Much of this increase is independent of changes in translocation to and from the leaflet. Interruption of translocation through living cells by detachment of leaflets or steam damage to the petiolules produces increased ribonuclease activity, but this activity is ...

Electrophoretic studies on purified crystalline ribonuclease showed the absence of any impurities differing in mobility from the bulk of material. The isoelectric point of ribonuclease was found by electrophoresis to be at about pH 7.8. Ultracentrifuge studies indicated fair homogeneity of ribonuclease in solution. Only one moving component has been observed. The molecular weight of ribonucleas...

Bovine pancreatic ribonuclease has been studied as the substrate of a number of proteolytic enzymes. In the native state it is completely resistant to trypsin and chymotrypsin (1, 2), but denaturation by chemical (3) or physical (4, 5) means induces susceptibility to these enzymes. Ribonuclease is! however, susceptible to attack by a number of other proteases. Subtilisin has been shown to cause...