Open AccessThe Association of Ribosomal Subunits of Escherichia coli
Author(s) -
Diggelen Otto P.,
Bosch Leendert
Publication year - 1973
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1973.tb03149.x
Subject(s) - protein subunit , ribosome , transfer rna , ribosomal rna , escherichia coli , eukaryotic large ribosomal subunit , biology , biochemistry , polyacrylamide gel electrophoresis , eukaryotic ribosome , specificity factor , rna , chemistry , enzyme , gene , rna polymerase
Association between ribosomal subunits of Escherichia coli can lead to the formation of two classes of 30‐S · 50‐S couples. The first class sedimenting between 50 S and 70 S, arises when native subunits associate, the second sedimenting at 70 S upon coupling of so‐called derived subunits. From cross experiments it is concluded that it is the 50‐S subunit which determines the nature of the association product, whereas the 30‐S subunit determines whether an association product can be formed. Native and derived 50‐S subunits are indistinguishable by sucrose gradient centrifugation and do not differ qualitatively in their ability to form polypeptides under the directions of bacteriophage RNA. Native 30‐S subunits lose a factor during isolation, probably IF‐3. They are therefore able to associate at 0° and 37 °C. On the other hand derived 30‐S subunits are unable to associate at 0 °C but they do so at 37 °C in the presence of 10 mM Mg 2+ . A number of trivial factors have been excluded to explain the difference between the two types of 50‐S subunits. The preparation method is not responsible for the difference. Nor do the derived subunits contain peptidyl‐tRNA, known to influence subunit association. The content of tRNA and aminoacyl‐tRNA has been determined quantitatively by polyacrylamide‐gel electrophoresis. None of the subunits nor the 70‐S ribosomes from which the derived subunits are prepared contain a tRNA species.