Purified low-molecular-weight protein kinase from murine sarcoma virus particles catalyzes tyrosine phosphorylation endogenously but phosphorylates cellular proteins at serine

The low-molecular-weight (LMW) protein kinase associated with high-titer murine sarcoma virions have been extensively purified by ammonium sulfate fractionation. Bio-Gel P-100 gel filtration, DEAE-cellulose and carboxymethyl cellulose chromatography. The purified enzyme migrates as a 16K polypeptide in polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme catalyzes phosphotransfer with ATP as a phosphate donor to various exogenously added proteins as acceptors; it requires Mg2+ and is independent of cyclic AMP. The enzyme preparation catalyzes a low level of phosphorylation in the absence of any exogenously added substrate and forms phosphotyrosine. However, in the presence of acceptor protein molecules including total soluble cytoplasmic proteins of murine sarcoma virus-transformed mouse cells, the phosphorylated end products contain predominantly phosphoserine. The virion-associated enzyme also shows a preference for phosphorylating certain polypeptides in the soluble cytoplasmic extracts of murine sarcoma virus-transformed cells.

The structure and thermotropic properties of pure 1,2-diacylgalactosylglycerols in aqueous systems

Pure 3-sn-monogalactosyldilinolenoylglycerol and 3-sn-digalactosyldilinolenoylglycerol have been isolated from bean leaves. Distearoyl derivatives have been prepared by catalytic hydrogenation of the unsaturated galactolipids. The unsaturated lipids form stable monomolecular films at the air/water interface which are similar to liquid-expanded phospholipid monolayers. The limiting areas were about 0.57 nm2 and 0.62 nm2 for the mono- and digalactosyldiacylglycerols, respectively. The saturated galactolipids formed condensed monolayers that were relatively unstable. The surface pressure-area isotherm of the digalactosyl derivative was more expanded than that of the monogalactosyldiacylglycerol especially at low surface pressures. Low-angle X-ray diffraction and freeze-fracture electron microscopy studies of the monogalactosyldiacylglycerols showed that an hexagonal-type structure was formed by the unsaturated lipid in aqueous systems, whilst the saturated lipid was arranged in a lamellar configuration. Both digalactosyldiacylglycerols form lamellar structures in water. A gel-to-liquid-crystalline phase transition of distearoyldigalactosylglycerol was observed at about 51 degrees C by fluorescence depolarization measurements, using 1,6-diphenylhexatriene, and by differential scanning calorimetry. The saturated monogalactosyldiacylglycerol did not form dispersions suitable for fluorescence probe studies of a phase transition. A complex pattern of endotherms was observed for this lipid by differential scanning calorimetry.

The crystal structure of tortoise egg-white lysozyme at 6 A resolution

Lysozyme extracted from the egg-white of tortoise, the first example of a reptilian lysozyme to have been purified, has been crystallized and its tertiary structure determined at low resolution by X-ray analysis. This structure is shown to be closely homologous to that of hen egg-white lysozyme. The crystals of tortoise egg-white lysozyme contain a large proportion of liquid and the X-ray map shows that this forms large channels through the crystals into which the active sites of the enzyme molecules open. This indicates that tortois lysozyme crystals may be suitable for low-temperature studies of true enzyme substrate complexes.

Direct association of fibronectin and actin molecules in vitro

Affinity chromatography with actin-Sepharose conjugates of purified human fibronectin, normal human plasma, or serum-free culture fluid from human fibroblasts showed that fibronectin molecules can directly bind to actin. A quantitative recovery of soluble human fibronectin was accomplished by chromatography on actin immobilized on Sepharose beads. Human fibronectin molecules bound to actin-Sepharose were eluted with 0.25--0.35 M potassium bromide, and these molecules competed in a species-specific radioimmunoassay for human fibronectin. The subunits of fibronectin isolated by actin-Sepharose chromatography comigrated in SDS polyacrylamide gel electrophoresis with those of electrophoretically homogeneous fibronectin purified by conventional procedures. The efficient direct binding of fibronectin to actin suggests that interactions between these proteins might also take place in vivo but further studies are needed to elucidate the biological significance of this affinity.

Thermolabile protein kinase molecules in a temperature-sensitive murine sarcoma virus pseudotype

Murine sarcoma virus-associated protein kinases that bind to actin have been purified by affinity chromatography on actin coupled to Sepharose. Heat inactivation studies showed the presence of thermolabile enzyme activity in pseudotypes containing a temperature-sensitivity mutant of murine sarcoma virus (MSV) but not in two independent wild-type MSV pseudotypes. Studies with Sephadex G-75 column fractions showed that a low molecular weight form, approximately 15,000, is the major thermolabile kinase in the temperature-sensitive MSV virions. Antibodies raised against the MSV-coded p60 protein, when added to the in vitro reaction mixtures, showed specific phosphorylation of the IgG heavy chain and a simultaneous reduction in the extent of phosvitin phosphorylation catalyzed by the various MSV pseudotype kinases. Thus a transforming retrovirus-coded enzyme activity that interacts directly with a major cytoskeletal protein and whose activity parallels the transforming ability of a conditional MSV mutant has now been identified.

A murine sarcoma virus-associated protein kinase: interaction with actin and microtubular protein

A low molecular weight (LMW) protein phosphokinase enzyme that binds to actin has been isolated from murine sarcoma virions; this kinase activity is not present in nontransforming murine leukemia viruses. Sephadex G-75 gel filtration and affinity chromatography on actin-Sepharose conjugates allow a significant level of purification of this enzyme. The enzyme associates with microtubular proteins and inhibits the in vitro polymerization of microtubules. This study represents the first isolation of a sarcoma virus-associated protein that possesses the ability to interact directly with two major components of the cytoskeletal system.

A rapid method for the purification of extrachromosomal DNA from eukaryotic cells

A simple and efficient procedure to purify the low molecular weight extrachromosomal DNA from eukaryotic cells is described. Gentle lysis of cells with urea and sodium dodecyl sulfate in 0.24 M phosphate buffer (pH 6.8) is followed by the removal of high molecular weight bulk DNA by centrifugation. Protein and RNA are removed from the supernatant by hydroxyapatite chromatography in urea/phosphate buffer. Urea is then removed with 0.15 M phosphate buffer and the extrachromosomal DNA, virtually free from protein and RNA, is finally eluted in 0.5 M phosphate buffer. The procedure allows the recovery of about 99% simian virus 40 (SV40) DNA from infected monkey kidney cells in the extrachromosomal fraction. In normal mouse, monkey, andhuman cells, approximately 1% of total cell DNA appears to be extrachromosomal.

Molecular diversity among five different endogenous primate retroviruses

Genetically transmitted retroviruses of Old and New World monkeys include type C viruses isolated from baboons (M7), macaque (MAC-1), and owl monkeys (OMC-1) and type D viruses from langurs (PO-1-Lu) and squirrel monkeys (SMRV, M534). Each of these isolates is unrelated to the others by nucleic acid hybridization criteria and contains a unique array of virion-associated proteins which can be resolved by agarose gel filtration and polyacrylamide gel electrophoresis under denaturing conditions. The major structural protein of each virus has a distinct primary structure, as determined by two-dimensional tryptic peptide analysis, and is antigenically different from the others. The major virion phosphoproteins of endogenous primate type C viruses (pp15) are also different from those of type D viruses (pp13-pp14). Immunological and structural analyses show that the endogenous langur virus and the horizontally transmitted Mason-Pfizer virus of rhesus monkeys are closely related to one another, consistent with the sequence homology detected in their RNA genomes. Although certain radioimmunoassays detect interspecies antigenic determinants common to either the p30 or gp70 proteins of some of these viruses, no one assay has yet been designed which can detect all groups of endogenous primate retroviridae. The data lead to the conclusion that primates contain a minimum of three different sets of genetically transmitted type C and type D retroviral genes.

Studies on L-ascorbic acid metabolism in rats under chronic toxicity due to organophosphorus insecticides: effects of supplementation of L-ascorbic acid in high doses

The effects of chronic administration of two organophosphorus insecticides, parathion and malathion on the growth rate, ascorbic acid metabolism and some other nutritional and physiological parameters in rats were studied. Both parathion and malathion toxicity retarded the growth rate of rats. Inhibition of brain acetylcholinesterase was taken as an index of organophosphorus insecticide toxicity. Haemoglobin concentration of blood and organ weights were not affected under the toxic conditions. Parathion and malathion administration stimulated the activity of L-gulonolactone oxidase along with a simultaneous increase in the tissue storage and urinary excretion of vitamin C. The activities of other enzymes of ascorbic acid metabolism, dehydroascorbatase, uronolactonase, and L-gulonate dehydrogenase and decarboxylase were altered under the experimental conditions. Only minor histological changes of the liver and kidney tissues were noted under parathion and malathion toxicities. Excess intake of vitamin C under the toxic conditions was found to be very effective in counteracting the growth retardation and also the alterations produced by parathion and malathion both at the enzymatic and histological levels.

Rescue of endogenous 30S retroviral sequences from mouse cells by baboon type C virus

Mus musculus SC-1 cells were infected with M7 baboon type C virus. The progeny of this infection included viral pseudotypes that contained M7 helper virus and endogenous 30S retrovirus-associated sequences derived from SC-1 cells (RAS). The RAS sequences are unrelated by nucleic acid hybridization criteria to previously described types of murine retroviruses and do not code for known murine viral structural proteins. The RAS genome is present in multiple copies in the DNA of laboratory (M. musculus) and Asian (M. caroli and M. cervicolor) mice, is expressed in the RNA of uninfected mouse cells, and can be efficiently rescued by type C, but not type B, viruses. RAS is closely related to 30S virus-associated RNA in NIH/3T3 and BALB/c JLSV-9 cells and may be analogous to the defective 30S RNA sequences found in rats.

Species-specific cellular DNA-binding proteins expressed in mouse cells transformed by chemical carcinogens

Mouse cells transformed by DNA and RNA tumor viruses and by chemical carcinogens have been examined for the presence of specific DNA-binding proteins by DNA-cellulose chromatography. Using mouse DNA-cellulose we have obtained single-stranded DNA-binding proteins from two clones transformed by chemical carcinogens. Simian virus 40 transformants also have a DNA-binding protein [the tumor (T) antigen] that binds to mouse and human DNA with comparable affinity. Mouse sarcoma virus-transformed cells and two other chemically transformed clones showed no difference in DNA-binding protein pattern compared to the untransformed parental cell. The DNA-binding proteins isolated from the chemically transformed cell clones are between 25,000 and 30,000 daltons by sodium dodecyl sulfate/polyacrylamide gel electrophoresis. These cellular "T proteins" bind to the homologous mouse cellular DNA with a higher affinity than to heterologous human cellular DNA.

Pseudotypes of feline sarcoma virus contain an 85,000-dalton protein with feline oncornavirus-associated cell membrane antigen (FOCMA) activity

Feline sarcoma virus (FeSV) rescued from transformed nonproducer mink or rat cells contains two FeSV-specific antigens (p15 and p12), and the feline oncornavirus-associated cell membrane antigen (FOCMA). All three antigens are helper virus-independent and are encoded by the FeSV genome, FOCMA, p15, and p12 antigens cochromatograph as phosphorylated molecules of 85,000 molecular weight (pp85), adsorb to immunoadsorbant columns prepared with antibodies to feline leukemia virus (FeLV), and are precipitated with antisera to FeLV or FOCMA. Antibodies to FOCMA can be adsorbed with fractions containing pp85 but not with FeLV proteins, including p15 and p12. Thus, a virus-coded tumor antigen which immunizes cats against tumors induced by feline type C viruses is packaged in FeSV particles and is linked to viral structural protein.

Endogenous New World primate type C viruses isolated from owl monkey (Aotus trivirgatus) kidney cell line

A type C virus (OMC-1) detected in a culture of owl monkey kidney cells resembled typical type C viruses morphologically, but was slightly larger than previously characterized mammalian type C viruses. OMC-1 can be transmitted to bat lung cells and cat embryo fibroblasts. The virions band at a density of 1.16 g/ml in isopycnic sucrose density gradients and contain reverse transcriptase and a 60-65S RNA genome composed of approximately 32S subunits. The reverse transcriptase is immunologically and biochemically distinct from the polymerases of othe retroviruses. Radioimmunoassays directed to the interspecies antigenic determinants of the major structure proteins of other type C viruses do not detect a related antigen in OMC-1. Nucleic acid hybridization experiments using labeled viral genomic RNA or proviral cDNA transcripts to normal cellular DNA of different species show that OMC-1 is an endogenous virus with multiple virogene copies (20-50 per haploid genome) present in normal owl monkey cells and is distinct from previously isolated type C and D viruses. Sequences related to the OMC-1 genome can be detected in other New World monkeys. Thus, similar to the Old World primates (e.g., baboons as a prototype), the New World monkeys contain endogenous type C viral genes that appear to have been transmitted in the primate germ line.

Production of protein by fungi from agricultural wastes. I. Standardization of certain factors for maximum protein production

Several fungi were screened for protein production in a simple medium using either sugarcane bagasse, wheat straw or cowdung as substrate. Out of them Rhizoctonia melongina, Pleurotus ostreatus, and Coprinus aratus proved promising and were taken up for further studies. Optimum conditions of temperature, incubation, and pH for maximum growth and protein production by the three fungi were then ascertained and standardized.

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.