Studies of E. coli Ribosomal RNA and Its Degradation Products

Abstract

The RNA of E. coli ribosomes has been extracted by the phenol method. The 70S ribosomes contain RNA molecules of 28 and 18S almost exclusively. When the 70S ribosomes are dissociated to 30 and 50S ribosomes the former contain only the 18S RNA and the latter a mixture of 28 and 18S RNA. There are also present, however, small quantities of ribosomal RNA having sedimentation coefficients of between 4 and 8S. These small molecules are particularly abundant in the smaller ribosomes present in the cell extract and account for most of the RNA of 20S ribosomes.In addition it has proved possible to degrade the large molecules of RNA to a series of smaller molecules. Removal of magnesium ions from the growing cell, extensive dialysis of the RNA against a buffer of low ionic strength, and heating all resulted in such degradation. Three degradation products were observed having sedimentation coefficients of about 13.1S, 8.8S, and 4.4S. The integral sedimentation distributions of these preparations suggest a high degree of homogeneity among the molecules of each of the three classes. The three sizes seem to result from sequential breaks in the molecules since the proportion of smaller molecules increases with time of treatment.The molecular weights of the 8.8S and 4.4S molecules have been estimated as 144,000 +/- 4,900 and 29,200 +/- 1,200 respectively by the Archibald method.

Isolation and Physical Properties of the Ribosomal Ribonucleic Acid of Escherichia coli*

“…Sedimentation Properties, The schlieren pattern of the unfractionated ribosomal RNA is depicted in Figure 1. This distribution is characteristic of E. coli ribosomal RNA and has been widely quoted in the literature (Littauer and Eisenberg, 1959;Hall and Doty, 1959; Aronson and McCarthy, 1961). The dependence of the sedimentation coefficients upon the total RNA concentration is illustrated in Figure 2 and the effect of ionic strength in Figure 3.…”

Non-coding RNA gene families in the genomes of anopheline mosquitoes

“…Several distinct RNA species have been detected during the last years in addition to the “classical” three RNA classes, mRNA [ 5 , 6 ], rRNA [ 7 ] and tRNA [ 8 ] that helped describe the central dogma of Molecular Biology established as such later [ 9 ]. The vast majority of those RNA species is known to not encode polypeptides; they are, therefore, collectively branded as non-coding RNAs or ncRNA [ 10 ].…”

The Atypical Ribosomal RNA Complement of Rhodopseudomonas spheroides

“…The studies of Aronson & McCarthy (1961) have suggested that 16s and 23s ribosomal RNAs are built from multiples of a single subunit, the 23s particle being viewed as a dimer of 16s RNA. This view is supported by the work of Spahr & Tissieres (1959), which showed that the 30s and 50s ribosomes of Escherichia coli had similar nucleotide compositions, and the work of Petermann & Pavlovec (1963), which indicated that there was interconversion between the 18s and 28s RNA particles of rat liver ribosomes.…”