The use of azidoarylimidoesters in RNA-protein cross-linking studies with Escherichia coli ribosomes

A series of related hetero-bifunctional RNA-protein cross-linking reagents has been prepared, carrying an imidoester or N-hydroxysuccinimide ester function at one end of the molecule, and a phenylazido function at the other. These compounds have been applied to RNA-protein cross-linking studies with ribosomal subunits, and one of them, p-azido-phenylacetic imidoester, has proved to be a particularly useful reagent for this purpose. The reagent first reacts specifically with protein amino groups, and subsequent photolysis of the azide group leads to cross-linking to the RNA in yields of up to 8% of the total protein. The whole reaction takes place under very mild conditions in aqueous solution.The individual proteins concerned in the cross-links have been identified by two-dimensional gel electrophoresis, and the existence of a covalent cross-link was confirmed by the isolation by two different methods of protein-oligonucleotide complexes carrying a ³²P label. Although most of the ribosomal proteins could be cross-linked to their corresponding ribosomal RNA within the individual subunits, RNA-protein cross-links at the ribosomal subunit interface were only detectable in vanishingly small amounts.The advantages of this type of genuine hetero-bifunctional reagent in RNA-protein cross-linking studies are discussed.     

Nickel requirement for chemolithotrophic growth in hydrogen-oxidizing bacteria

In a comparative study the requirement of several strains of autotrophic hydrogen-oxidizing bacteria for nickel was examined. Autotrophic growth was studied both in liquid media, previously freed from trace metals; and on solidified media, using a plate diffusion assay. The latter assay was based on the observation that EDTA causes complete inhibition of autotrophic growth on agar medium as a result of nickel deficiency. Nickel was shown to be required as a trace element in five strains of Alcaligenes eutrophus, in two strains of Xanthobacter autotrophicus, in Pseudomonas flava, in Arthrobacter spec. 11X and in strain 12X. In these bacteria nickel was not replaceable by cobalt, copper, manganese or zinc ions. No significant nickel requirement was detected by these methods, however, for Paracoccus denitrificans and Nocardia opaca 1b.     

Alterations in plasma-membrane functions after poliovirus infection

After exposure of HeLa cells to poliovirus there is a rapid decline (within minutes) in fluorescence polarization of DPH (1,6-diphenyl-1,3,5-hexatriene). Within one hour after infection the (Na+/K+)ATPase activity of an isolated plasma-membrane-rich fraction is enhanced, the cell volume decreases, and the intracellular concentration of a potent low-molecular-weight inhibitor of host protein synthesis increases.     

Different repetition frequencies of a 120 base-pair DNA-element and its arrangement in Chironomus thummi thummi and Chironomus thummi piger

The repetition frequency of a highly repetitive DNA sequence has been measured in the genomes of Ch. thummi thummi and Ch. th. piger. This sequence is known to be involved in the evolutionary duplication of defined chromosomal segments leading to a significant increase in the genome size of Ch. th. thummi. Reassociation of this highly repetitive DNA sequence which has a repeat length of 120 base-pairs, with total Ch. th. thummi and Ch. th. piger DNA has shown that the repetition frequency in the Ch. th. thummi DNA is 5.5 fold higher than in Ch. th. piger. In both genomes a 120 base-pair sequence is present as tandemly repeated sequence as shown by Southern analysis.     

Catalytic activity and arrangement of subunit polypeptides in rat liver cytochrome c oxidase as studied by proteolysis

Cytochrome c oxidase from rat liver was incubated with various proteinases of different specificities and the enzymic activity was measured after various incubation times. A loss of catalytic activity was found after digestion with proteinase K, aminopeptidase M and a mitochondrial proteinase from rat liver. In each case the decrease in enzymic activity was compared with the changes in intensities of the polypeptide pattern obtained after sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibilities of the subunit polypeptides of the soluble cytochrome c oxidase to proteinases were very different. Whereas subunit I was most susceptible, subunits V–VII were rather resistant to degradation. From the relative inaccessibility of subunits V–VII to proteinases it is likely that these polypeptides are buried in the interior of the enzyme complex.     

Hydrophobic interactions of cytochrome c oxidase. Application to the purification of the enzyme from rat liver mitochondria.

The binding of rat liver cytochrome c oxidase to phenyl-Sepharose and various alkyl and omega-aminoalkyl agarose gels has been studied. Deoxycholate-solubilized cytochrome c oxidase was tightly bound to hexyl, octyl, omega-aminohexyl, omega-aminooctyl agarose as well as to phenyl-Sepharose. This hydrophobic interaction was used for the purification of cytochrome c oxidase. The enzyme which was eluted from phenyl-Sepharose was devoid of NADH (NADPH)-acceptor reductase activities. The heme a content was 15.4 nmol per mg of protein. The purified enzyme was resolved into seven polypeptides upon polyacrylamide gel electrophoresis in sodium dodecylsulfate with molecular weights of 40,000, 23,200, 21,500, 14,500, 12,600, 8900, and 4900. Antibodies raised in rabbits against the pure enzyme did not cross-react with cytochrome c oxidases from either beef heart or yeast mitochondria. Cytochrome c oxidase bound to octyl-Sepharose or phenyl-Sepharose exhibited a very low catalytic activity. The possible modes of interaction of cytochrome c oxidase with the hydrophobic ligands are discussed.     

The effect of sodium chloride on the structure of ribonucleoprotein particles from rat liver nuclei.

38S (monoparticles) and greater than 50--200S ribonucleoprotein particles (polyparticles) from rat liver nuclei were treated with increasing concentrations of sodium chloride. Treatment of 38S or greater than 50--200S particles, with 0.14, 0.25, 0.5, 1.0, and 2.0M NaCl resulted in a decrease of protein to RNA ratios from 8 to 3.1 for 38S particles and from 4.0 to 1.5 for greater than 20--200S particles. Correspondingly the densities in CsCl increased. Whereas the maximum of the sedimentation profile of polyparticles decreased from 90S to 50S after treatment with increasing NaCl concentrations, a discontinuous change was found in the case of monoparticles. It was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis that the proteins which were dissociated by NaCl were in the molecular weight range of 30--45 000. Four of the 5 small molecular weight RNAs in the range of 4.5 to 8S remained tightly associated even after treatment of polyparticles with 2.0M NaCl. When 38S or 70--200S nRNP particles were exposed to increasing concentrations of NaCl (0.25, 0.5, 1.0, 2.0M), the molar ellipticity at 264 nm increased progressively to about 40%. Upon NaCl treatment of polyparticles and successive removal of the dissociated proteins by centrifugation the increase in the positive CD band at 264 nm was only 15%.     

Global classification of natural terrestrial ecosystems

Summary A global classification system of natural terrestrial ecosystems (including systematic notation), based on the climate zones of Walter, is presented. The basic units of the system are the ecological units biome and biogeocoene. The zonobiomes, which are climate zones corresponding to the largest vegetation units, are subdivided into subzonobiomes and these into individual biomes. The biomes are thus natural, geographical units within the climate zones. They are in turn subdivided into individual biogeocoenes and their constituent synusiae. In addition, the coordinate concepts of pedobiome and orobiome are introduced. These are distinguished from the zonobiomes as follows:1. the pedobiomes by extreme edaphic conditions which cause azonal vegetation.2. the orobiomes, as mountain ranges, by their vertical climate zonation and the altitudinal belts of vegetation.These relationships are explained, and two subseries of pedo-and oro-subunits are established. Transitional zones (zono-ecotones) between individual zonobiomes are also distinguished. The classification system is summarized in a schematic, and a world map of zonobiomes and zono-ecotones is included. More details are presented in Walter (1976).

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Zusammenfassung Ein globales Gliederungssystem der natürlichen terrestrischen Ökosysteme (einschließlich systematischen Bezeichnungen) wird in Beziehung zu den Walter'schen Klimazonen gesetzt. Grundeinheiten des Systems sind die ökologischen Einheiten Biom und Biogeozön. Die Zonobiome werden unterteilt in Subzonobiome und diese in Biome. Die Zonobiome sind Klimazonen und entsprechen den größten Vegetationseinheiten. Die Biome sind natürliche, geographische Einheiten innerhalb der Klimazonen. Sie werden bis zu einzelnen Biogeozönen und ihren Synusien (Teilsytemen) unterteilt. Parallel dazu werden die Begriffe Pedobiom und Orobiom eingeführt. Diese heben sich aus den Zonobiomen heraus: die Pedobiomen durch extreme Böden, die eine azonale Vegetation bedingen, die Orobiome als Gebirge durch die vertikale Klimagliederung und die Höhenstufen der Vegetation. Diese Beziehungen werden erklärt, und zwei Nebenreihen der Pedo- bzw. Orobiom-Untereinheiten werden aufgestellt. Zwischen den einzelnen Zonobiomen werden Übergangszonen (Zonoökotone) unterschieden. Das Gliederungssytem wird bereits in einem Schema zusammengefaßt, und eine Weltkarte der Zonobiome und Zonoökotone wird beigefügt. Ausführlich werden alle diese Fragen bei WALTER (1976) behandelt.

     

Mathematical analysis of multienzyme systems. II. Steady state and transient control.

The control theory of steady states, previously presented for linear enzymatic systems (Heinrich and Rapoport, 1974) is extended to nonlinear systems. On the basis of three theorems a new procedure for the calculation of the control strength and of the control matrix is developed. The theory is applied to the extended model of glycolysis of erythrocytes, which includes also ATP-consuming processes. Also in this model the glycolytic flux is mainly controlled by the hexokinase-phosphofructokinase-system. The control strengths of the pyruvate kinase and of the enzymes of the 2.3 P2G-bypass are negligibly small. The control strength of the ATPase is negative, i.e. an activation of this enzyme leads to a decrease of the flux. For transition states of multienzyme systems definitions are given for the mean time required for the transition of the metabolites and for the "transient control" of enzymes. Enzymes with a pronounced influence on the transition time are called time-limiting enzymes. Enzymes which excert strong control on the time-dependent processes may have little influence under steady state conditions and vice versa. The transition times of ATP have been calculated for transient states of glycolysis.     

Beiträge zur Vitalfärbung von Pilzmyzelien II

Ohne ZusammenfassungBeitr. z. Vitalf. v. Pilzmyzelien I; Flora134, S. 58, 1939.