Phosphorylation of murine type C viral p12 proteins regulates their extent of binding to the homologous viral RNA

The purified p12 phosphoprotein of Rauscher murine leukemia virus was fractionated by ion exchange chromatography into subpopulations of molecules containing different amounts of covalently linked phosphate. Of the various phosphorylated forms of p12 protein purified from virions, only a species containing relatively little phosphate can bind in vitro to purified homologous 70S viral RNA. Using ultraviolet irradiation to stabilize ribonucleoprotein complexes in intact virions, the same molecular species of p12 phosphoprotein can be isolated in close association with the 70S viral genome. The results show that phosphorylation of type C viral p12 proteins influences the extent, but not the specificity, of their interaction with homologous viral RNA.

Stepwise selection of efficient rhizobial cultures through cultural characteristics

Nodulation and shoot nitrogen of two varieties of soybean (Glycine max) were studied with twenty strains of Rhizobium japonicum. A number of cultural characteristics of the strains in isolation to the symbiotic system were also studied. A stepwise selection method was employed for detecting efficient cultures through the cultural characteristics which showed association with the steps in the symbiotic system. Nodulation of one variety was found to be associated with the dehydrogenase activity and the growth of microbes in the medium containing soil extract, whereas the nodulation of another variety showed association with the growth in the media containing asparagine and tryptophane. The shoot nitrogen of one nodulated cultivar correlated with the microbial growth in Elkan's medium in the medium containing serine and glucose, whereas the shoot nitrogen of the other nodulating variety correlated with the growth of the cultures in the medium containing aspartic acid. The validity of this approach to the problem for detecting efficient strains through cultural characteristics was discussed.

The genome-associated, specific RNA binding proteins of avian and mammalian type C viruses

A structural protein purified from the Rous sarcoma virus (RSV) can specificially bind in vitro to purified avian, but not mammalian, type C viral RNA. Following ultraviolet irradiation of viral particles under conditions which stabilize the polyploid 70S viral RNA, the same polypeptide can be directly purified from the RSV genome. Based on its electrophoretic mobility in polyacrylamide gels containing sodium dodecylsulfate, the RNA binding protein has been identified as the major phosphoprotein (p19) of avian type C viruses. Similar experiments show that the major phosphoproteins of mammalian type C viruses (p12 for murine viruses and p16 for endogenous primate viruses) are also the specific RNA binding proteins and, similarly, are found closely associated with the 70S RNA genomes in the intact viral particles.

Grouping of rhizobial strains--a method based on symbiotic characteristics

Twenty strains of Rhizobium japonicum and non-inoculated control were used to study seven symbiotic characteristics with two varieties of soybean (Glycine max). The strains were then grouped on the basis of these symbiotic characteristics, using Mahalanobis' D2 statistical method. Eight groups were formed in which two strains stood distinctly aloof, indicating thereby the exceptional nature of these strains over others in their symbiotic behaviour. This method is suggested for selecting exceptional strains for particular symbiotic characteristics as well as for greater N fixing efficiency with varieties and for different agroclimatic conditions.

Specificity of in vitro binding of primate Type C viral RNA and the homologous viral p12 core protein

The binding of type C viral p12 proteins to purified viral RNA has been examined in vitro with the use of a family of closely related infectious primate type C viruses--the woolly monkey (SSAV) and gibbon (GALV) group. This in vitro protein-RNA binding is type specific. The system should serve as a model for studies of the evolution of nucleic acid binding proteins.

Specific binding of the type C viral core protein p12 with purified viral RNA

The major viral phosphoproteins (p12) of the Rauscher murine leukemia virus (R-MuLV) and the simian sarcoma-associated virus (SSAV) bind in vitro to their homologous 70S and 35S viral RNAs. Using purified 32P-labeled RNA and 125I-labeled p12 protein, complexes that are stabilized by formaldehyde-cross-linking can be readily detected after velocity gradient centrifugation. The in vitro reconstructed ribonucleoprotein complexes are seen only with p12 proteins incubated with viral RNAs isolated from the same type C viruses; no such complexes form with heterologous protein-RNA mixtures. Homologous but not heterologous p12 molecules compete with radiolabeled p12 protein for the specific viral RNA binding sites. The competition assay permits the detection of 10 ng of viral p12 protein. The major internal protein of type C viruses (p30) does not bind to viral RNA using identical assay conditions. From the specific activities of the radiolabeled components and also by equilibrium sedimentation analysis, we estimate that fewer than 15 molecules of p12 protein bind to each molecule of viral RNA. Both the specificity and stoichiometry of the p12-RNA interactions suggest that these RNA tumor virus proteins have a regulatory role in cells.

The effect of set on the two-point tactual threshold

This experiment studies the influence of set on the two-point tactual threshold. The two-point limen (critical stimulus) was determined along the mid-longitudinal line of both volar and dorsal surfaces of the right forearms of seven university students. Test-stimuli were selected at 3 mm. steps both up and down from each of the critical stimuli. Each of these test-stimuli was presented separately, the critical stimulus being interpolated 30 times in each test of the series. The proportions of two-point and one-point responses to the critical stimulus were then determined again in a control series. It was found that, as the test-stimulus deviated in the positive direction from the critical stimulus, the proportion of two-point responses to the critical stimulus increased, reached a maximum and then began to decline. A similar rise and fall in one-point responses were found in the opposite direction. The results were explained by Adaptation Level Theory.

DNA replication in SV40-infected cells. XI. The properties of SV40 DNA and nucleoprotein complex synthesized in the presence of cycloheximide

Cycloheximide inhibits simian virus 40 (SV40) DNA synthesis in productively infected African green monkey kidney cells. The residual viral DNA synthesized in the presence of this drug is deficient in superhelical turns as measured by band sedimentation in the presence of several concentrations of ethidium bromide. The superhelical density of SV40 DNA synthesized in the presence of cycloheximide is about one half that of viral DNA produced in the absence of this drug. Ribonuclease H and alkali treatment were employed to determine if ribonucleotides could be detected in closed circular SV40 DNA synthesized in the presence of cycloheximide. While both these approaches detected ribonucleotides in mitochondrial DNA, no identification of ribonucleotides in SV40 DNA synthesized in the presence of cycloheximide was found. The SV40 nucleoprotein complex synthesized in the presence of cycloheximide has a slower sedimentation rate (35S) and a higher bouyant density (1.54 g/cm3) than the complex made in the absence of this drug (50S; 1.47 g/cm3). The protein:DNA ratio of the SV40 nucleoprotein complex is normally about 0.9. This ratio is reduced to about 0.6 when the complex is synthesized in the presence of cycloheximide.