Mitochondrial tyrosyl transfer ribonucleic Acid in soybean seedlings

Soybean seedlings were examined for the presence of mitochondrial tRNA. Tyrosyl transfer tRNAs from whole cells, from a well characterized mitochondrial preparation, and from a snake venom phosphodiesterase-treated mitochondrial preparation, were compared by reverse phase chromatography. It was concluded that none of the three previously reported tRNA^Tyr species were mitochondrial. Rather, a fourth tRNA^Tyr species, eluting somewhat later, was of mitochondrial origin. Mitochondrial tRNA^Tyr was chromatographically similar to Escherichia coli tRNA^Tyr.     

Ribosomal ribonucleic acid and ribosomal precursor ribonucleic acid in Anacystis nidulans

The RNA of the blue-green alga Anacystis nidulans contains three ribosomal RNA species with molecular weights of 0.56x10(6), 0.9x10(6), and 1.1x10(6) if the RNA is extracted in the absence of Mg(2+). The 0.9x10(6)mol.wt. rRNA is extremely slowly labelled in (32)P-incorporation experiments. This rRNA may be a cleavage product of the 1.1x10(6)mol.wt. rRNA from the ribosomes of cells in certain physiological states (e.g. light-deficiency during growth). The cleavage of the 1.1x10(6)mol.wt. rRNA during the extraction procedure can be prevented by the addition of 10mm-MgCl(2). (32)P-pulse-labelling studies demonstrate the rapid synthesis of two ribosomal precursor RNA species. One precursor RNA migrating slightly slower than the 1.1x10(6)mol.wt. rRNA appears much less stable than the other precursor RNA, which shows the electrophoretic behaviour of the 0.7x10(6)mol.wt. rRNA. Our observations support the close relationship between bacteria and blue-green algae also with respect to rRNA maturation. The conversion of the ribosomal precursor RNA species into 0.56x10(6)- and 1.1x10(6)-mol.wt. rRNA species requires Mg(2+) in the incubation medium.     

Inhibition by soluble ribonucleic acid of stimulatory effect of liver template ribonucleic acid

1. Liver soluble RNA (s-RNA) and, to a smaller extent, Escherichia coli s-RNA inhibited the stimulation of [(14)C]leucine incorporation into protein in an E. coli S-30 system brought about by liver microsomal RNA or polyuridylic acid as template. 2. The inhibitory activity was associated with the fraction of the s-RNA possessing transfer-RNA activity. 3. The inhibition was exercised at a stage after charging of the s-RNA with amino acid. 4. Neither the method of preparation of the s-RNA nor its state of amino acid acylation affected its inhibitory action. 5. Stimulation of [(14)C]phenylalanine incorporation by polyuridylic acid or by liver microsomal RNA was not inhibited by addition of s-RNA. 6. It appears that excess of s-RNA inhibits the ambiguous incorporation of leucine with polyuridylic acid and also that something similar occurs with a natural template. 7. Estimation of messenger activity of samples of RNA should be carried out only after removal of s-RNA.     

Kinetics and template-dependency of ribonucleic acid synthesis by bacterial ribonucleic acid polymerase.

The rate of RNA synthesis catalysed by DNA-dependent RNA polymerase shows a Michealis-Menten-type saturation curve with increasing template concentration. However, the apparent Km is proportional to enzyme concentration, indicating that the reaction does not obey a simple kinetic scheme. The action of inhibitors also indicates a more complex interaction between the enzyme and the DNA template; many inhibitors of RNA synthesis either decrease Vmax. without affecting Km, or increase Km without affecting Vmax. All of these observations can be accounted for quantitatively by a reaction pathway in which the non-specific binding sites of the viral DNA template inhibit competitively the binding of the enzyme to the initiation sites. In terms of this pathway the two classes of inhibitors of RNA synthesis must then act predominantly either on the rate of elongation or on the availability of the binding sites respectively.