Ribonuclease isozymes in Chinese cabbage systemically infected with turnip yellow mosaic virus

Two-dimensional zymogram analysis of nucleases in Bacillus subtilis

A two-dimensional zymogram procedure for the analysis of nucleases is described. Isoelectric focusing (IEF) and nonequilibrium pH gradient electrophoresis (NEPHGE) were compared as first dimensions in combination with sodium dodecyl sulfate (SDS) electrophoresis as the second dimension in analyzing nucleases in lysates of Bacillus subtilis. All renaturable nucleases detected following SDS electrophoresis alone were resolved in NEPHGE-SDS electrophoresis gels whereas, in IEF gels, most either were at the basic end or were not present in the second-dimension gels. This method of analysis has revealed a complexity in nuclease species in B. subtilis not previously recognized. Eighty-three discreet nuclease activities have been detected in B. subtilis lysates. Using purified deoxyribonuclease I (bovine pancreas), as little as 10 pg of nuclease can be detected.

Use of polynucleotide/polyacrylamide-gel electrophoresis as a sensitive technique for the detection and comparison of ribonuclease activities

A technique is described in which the incorporation of a polynucleotide substrate into the matrix of a polyacrylamide gel allows the use of electrophoresis for the detection of polycationic ribonuclease activity rather than simply the presence of protein. Because use is made of the catalytic properties of ribonucleases, polynucleotide/polyacrylamide-gel electrophoresis is apparoximately 10(5) times more sensitive for the detection of these enzymes than conventional gel electrophoresis with the use of protein-staining dyes. Initial studies showed that the poor migration, in the gels, of highly charged polycationic ribonucleases in the presence of negatively charged synthetic polynucleotides could be overcome by high concentrations of spermine. The positively charged polyamine, by neutralizing the polyanionic polynucleotide, enabled these basic enzymes to migrate considerable distances in the gel. Electrophoresis of the RNAases under conditions of low pH, and incubation of the gel at neutral pH followed by staining for polynucleotide, resulted in coloured gels containing clear bands that define regions of enzyme activity. Alterations in spermine concentration or substrate identity caused changes in the positions of these bands, suggesting a dynamic interaction among the enzyme, polyamine and polynucleotide. Because of the advantages, in terms of selectivity and sensitivity of polynucleotide/polyacrylamide-gel electrophoresis, this technique was used to demonstrate the nuclease homogenity of three purified bovine muscle enzymes, and to compare these enzymes with each other, as well as with bovine pancreatic ribonuclease A.

Yeast protein synthesis. Preparation and analysis of a highly active cell-free system

A detailed description is given of the techniques for preparing, handling and assaying a cell-free protein-synthesizing system from yeast, analogous to crude (S-30) Escherichia coli extracts. Its basic characteristics are described. The rate of poly(U)-directed polyphenylalanine synthesis was at least fivefold higher than in previously reported yeast cell-free systems, approaching that of crude mammalian cell-free systems. Fractionation of the S-30 extracts lowered activity. Organelles and their fragments present in the S-30 extract neither contributed to nor inhibited cytoplasmic protein synthesis. There was a component localized in the high-speed supernatant that caused an inhibition of polyphenylalanine synthesis. Poly(U) programmed the synthesis of long-chain polyphenylalanine, in contrast with the only other yeast system in which this has been examined (Bretthauer & Golichowski, 1968). Preincubation techniques inactivated the system and probably a small proportion only of the ribosomes was active.