A species of low-molecular-weight ribosomal RNA, referred to as '4.5 S rRNA', was found in addition to 5 S rRNA in the large subunit of chloroplast ribosomes of a wide range of flowering plants. It was shown by sequence analysis that several variants of this RNA may occur in a plant. Furthermore, although in most flowering plants the predominant variant contains about 100 nucleotides, in the br...

Low concentrations (0.10 to 1.0 microgram/ml) of alpha-amanitin inhibit wheat embryo germination. Labeled RNA, synthesized in vivo by embryos imbibed in the presence of [3H]uridine and various concentrations of alpha-amanitin, was analyzed by oligo(dT)-cellulose chromatograhy and by gel electrophoresis (acrylamide and agarose) coupled with fluorography. Low concentrations of alpha-amanitin (0.1...

The regulation of ribosome formation in eukaryotic cells still remains an intractable problem despite the extensive knowledge available concerning the details of the nucleolar synthesis and processing of the rRNA. Within the nucleolus, which is the site of ribosome formation (2, 15, 20), a 45 S precursor is methylated and combined with ribosomal proteins during transcription (33); the 45 S prec...

The regulation of ribosome formation in eukaryotic cells still remains an intractable problem despite the extensive knowledge available concerning the details of the nucleolar synthesis and processing of the rRNA. Within the nucleolus, which is the site of ribosome formation (2, 15, 20), a 45 S precursor is methylated and combined with ribosomal proteins during transcription (33); the 45 S prec...

Mutants of an archaeon Halobacterium halobium, resistant to the universal inhibitor of translation, pactamycin, were isolated. Pactamycin resistance correlated with the presence of mutations in the 16 S rRNA gene of H. halobium single rRNA operon. Three types of mutations were found in pactamycin resistant cells, A694G, C795U and C796U (Escherichia coli 16 S rRNA numeration) located distantly i...

Specific ribonucleotides within the 5' domain of Escherichia coli 16 S rRNA were altered by deletion and/or substitution by site-directed mutagenesis of cloned DNA to assess the importance of these particular residues in defining the binding site for ribosomal protein S20. Gel filtration and sucrose gradient centrifugation were employed to measure the binding of ribosomal protein S20 to synthet...

When cells of S. typhimurium were heated at 48 C for 30 min in phosphate buffer (pH 6.0), they became sensitive to Levine Eosin Methylene Blue Agar containing 2% NaCl (EMB-NaCl). The inoculation of injured cells into fresh growth medium supported the return of their normal tolerance to EMB-NaCl within 6 hr. The fractionation of ribosomal ribonucleic acid (rRNA) from unheated and heat-injured ce...

Application of Sanger techniques to the analysis of the 3' terminal oligonucleotide from E. coli 32-P-labelled 16 S rRNA yields the sequence AUCACCUCCUUAOH. This sequence is identical in RNA isolated from two wild-type strains (MRE600 and E. coli B, SY106) and from a mutant strain (AB301/105) defective in RNase III. Data presented here explains the previous derivation of an incorrect sequence (...

The value of the rRNA chain elongation rate in bacteria is an important physiological parameter, as it affects not only the rRNA promoter activity but also the free-RNA polymerase concentration and thereby the transcription of all genes. On average, rRNA chains elongate at a rate of 80 to 90 nucleotides (nt) per s, and the transcription of an entire rrn operon takes about 60 s (at 37 degrees C)...

The interaction between RNA polymerase and the E. coli ribosomal (r) RNA promoter(s) of the rrnE operon has been studied by the filter-binding method. The extent of complex formation between RNA polymerase and rrnE promoter(s) is salt-dependent; ppGpp specifically inhibits interaction of RNA polymerase with the rrnE promoter(s). A tentative model is proposed for the molecular events in the earl...