Open AccessOn the Heterogeneity of Native Ribosomal Subunits in Ehrlich‐Ascites‐Tumor Cells Cultured in vitro
Author(s) -
VENROOIJ Walther J.,
JANSSEN Albert P. M.,
HOEYMAKERS Jan H.,
MAN Ben M.
Publication year - 1976
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1976.tb10319.x
Subject(s) - ribosomal rna , in vitro , ribosome , transfer rna , rna , microbiology and biotechnology , differential centrifugation , centrifugation , uridine , isopycnic , biochemistry , chemistry , density gradient , biology , physics , quantum mechanics , gene
Native small ribosomal subunits in cultured Ehrlich ascites tumor cells, analyzed by high‐resolution CsCl isopycnic centrifugation, consist of at least five classes of particles. These particles with buoyant densities of 1.39, 1.42, 1.45, 1.49 and 1.51 g/cm 3 were designated as S I , S II , S III , S IV and S V , respectively. They were different from the ribosome‐derived 40‐S subunits which have a density of 1.54 g/cm 3 . Native large ribosomal subunits consist of at least two classes of particles with densities of 1.57 g/cm 3 (L I ) and 1.59 g/cm 3 (L II ), respectively. The ribosome‐derived 60‐S subunits have the same buoyant density as L II particles. Labeling of Ehrlich ascites cells with radioactive uridine and a subsequent chase in the presence of RNA‐synthesis inhibitors shows that radioactivity was incorporated first in precursor particles with a density of 1.48 g/cm 3 and then subsequently appeared in S III and S II particles. Met‐tRNA f is found exclusively on native 40‐S particles with densities of 1.42 and 1.49 g/cm 3 . This result has been observed in cells labeled with [ 35 S] methionine in vivo as well as with tRNA charged in vitro. The possibility that S II particles contain 40‐S initiation complexes is discussed