In the course of an investigation of the chemical phosphorylation of ribonucleasel (cf. (l)), it became necessary to develop a chromatographic procedure for the fractionation of the phosphorylated protein. The method of Hirs et al. (2), employing the weak cation exchanger Amberlite XE-64, is an extremely valuable method for the chromatographic purification of pancreatic ribonuclease, but the us...

The erythroid-cell maturation is characterized by a series of complex morphological and biochemical events which in a relatively short period of time (70h) convert the committed haematopoietic stem cell into the mature anucleate erythrocyte. Despite our progress in the understanding of some aspects of erythropoiesis, the molecular mechanisms which control the progressive disappearance of subcel...

The interaction of ribonuclease A with cupric and zinc ions has been studied spectrophotometrically and by potentiometric titration in the presence and absence of cytidylic acid derivatives. In the absence of cytidylic acid, the results suggest that each cupric ion distributes among a set of approximately four spectrally similar sites; each site appears to consist mainly of a single imidazole s...

S proteins, pistil-specific ribonucleases that cosegregate with S alleles, have previously been shown to control rejection of self-pollen in Pefunia inflafa and Nicofiana alafa, two solanaceous species that display gametophytic self-incompatibility. The ribonuclease activity of S proteins was thought to degrade RNA of self-pollen tubes, resulting in the arrest of their growth in the style. Howe...

Three different strains of Streptomyces aureofaciens produce the homologous ribonucleases Sa, Sa2 and Sa3. The crystal structures of ribonuclease Sa (RNase Sa) and its complexes with mononucleotides have previously been reported at high resolution. Here, the structures of two crystal forms (I and II) of ribonuclease Sa2 (RNase Sa2) are presented at 1.8 and 1.5 A resolution. The structures were ...

Incubation of barley (Hordeum vulgare L. cv Himalaya) half-seeds with gibberellic acid enhances the secretion of ribonuclease and deoxyribonuclease from aleurone tissue (MJ Chrispeels, JE Varner 1967 Plant Physiol 42: 398-406; L Taiz, JE Starks 1977 Plant Physiol 60: 182-189). These activities were over 50-fold greater in medium of half-seeds incubated with gibberellic acid than in control medi...

The inhibition of ribonuclease Bi by 3'-N-hydroxyurea-3'-deoxythymidine 5'-phosphate is enhanced by 30-fold in the presence of Zn(2+). Thus, an N-hydroxyurea nucleotide can recruit Zn(2+) to inhibit the enzymatic activity of a ribonuclease. This result engenders a general strategy for the inhibition of non-metalloenzymes by metal complexes.