Nuclear S1 proteins from the starfish Asterina pectinifera.

Nuclear S1 proteins are a group of proteins apparently ubiquitous in vertebrate cell nuclei. They were originally isolated at pH 4.9 from the supernatant of rat liver nuclei mildly digested with DNase I. In the present study, under the conditions identical to those employed for vertebrate cells, we identified two S1 proteins in the starfish Asterina Pectinifera. Their molecular weights are 47,200 and 39,000. This finding suggests widespread occurrence of S1 proteins in eukaryotes and their basic function in the cell nucleus.     

Shape of proteins S3 and S17 from the small subunit of Escherichia coli ribosome.

The shapes of proteins S3 and S17 purified from the 30 S subunit of Escherichia coli A19 were studied by hydrodynamic methods. The proteins have s020,w values of 2.1 +/- 0.1 S and 1.2 +/- 0.1 S and D020,w values of 7.4 +/- 0.5 . 10(-7) cm2/s and 11.4 +/- 0.6 . 10(-7) cm2/s. The respective molecular weights determined by sedimentation equilibrium are 25 800 +/- 500 and 9900 +/- 300. The intrinsic viscosity values for the two proteins are 5.8 +/- 0.3 ml/g and 4.2 +/- 0.2 ml/g. From these hydrodynamic parameters a slightly elongated shape for S3 and a globular shape for S17 have been concluded.     

Cathepsin S from bovine spleen. Purification, distribution, intracellular localization and action on proteins.

Cathepsin S was detected in bovine kidney, spleen, lymph nodes and lung by immunochemical methods. The immunostaining of cathepsin S in kidney was concentrated to the cells of the proximal tubule, where the enzyme was present in cytoplasmic granules. The purification method for cathepsin S from bovine spleen involved (NH4)2SO4 fractionation, chromatography on CM-Sephadex C-50, gel filtration on Sephacryl S-200 and chromatofocusing (pH 8.0-6.0). The enzyme was partially destroyed by autolysis of the homogenate at pH 4.2. The isoelectric point of cathepsin S was 7.0. Cathepsin S was found to hydrolyse proteins at a similar rate to cathepsin L below pH 7.0. At pH values of 7.0-7.5 cathepsin S retained most of its activity, whereas cathepsin L was completely inactive.     

Specific protein kinase from Saccharomyces cerevisiae cells phosphorylating 60S ribosomal proteins.

A protein kinase, specific for 60S ribosomal proteins, has been isolated from Saccharomyces cerevisiae cells, purified to almost homogeneity and characterized. The isolated enzyme is not related to other known protein kinases. Enzyme purification comprised three chromatography steps; DEAE-cellulose, phosphocellulose and heparin-Sepharose. SDS/PAGE analysis of the purified enzyme, indicated a molecular mass of around 71 kDa for the stained single protein band. The specific activity of the protein kinase was directed towards the 60S ribosomal proteins L44, L44', L45 and a 38 kDa protein. All the proteins are phosphorylated only at the serine residues. None of the 40S ribosomal proteins were phosphorylated in the presence of the kinase. For that reason we have named the enzyme the 60S kinase. An analysis of the phosphopeptide maps of acidic ribosomal proteins, phosphorylated at either the 60S kinase or casein kinase II, showed almost identical patterns. Using the immunoblotting technique, the presence of the kinase has been detected in extracts obtained from intensively growing cells. These findings suggest an important role played by the 60S kinase in the regulation of ribosomal activity during protein synthesis.     

Zinc finger-like motifs in rat ribosomal proteins S27 and S29.

The primary structures of the rat 40S ribosomal subunit proteins S27 and S29 were deduced from the sequences of nucleotides in recombinant cDNAs and confirmed by determination of amino acid sequences in the proteins. Ribosomal protein S27 has 83 amino acids and the molecular weight is 9,339. Hybridization of cDNA to digests of nuclear DNA suggests that there are 4-6 copies of the S27 gene; the mRNA for the protein is about 620 nucleotides in length. Ribosomal protein S29 has 55 amino acids and the molecular weight is 6,541. There are 14-17 copies of the S29 gene and its mRNA is about 500 nucleotides in length. Rat ribosomal protein S29 is related to several members of the archaebacterial and eubacterial S14 family of ribosomal proteins. S27 and S29 have zinc finger-like motifs as do other proteins from eukaryotic, archaebacterial, eubacterial, and mitochondrial ribosomes. Moreover, ribosomes and ribosomal subunits appear to contain zinc and iron as well.