Open AccessDifferent Species of 70S Ribosomes of Escherichia coli and their Dissociation into Subunits
Author(s) -
Duin Jan,
Dieijen Gerbrandt,
Knippenberg Peter H.,
Bosch Leendert
Publication year - 1970
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1970.tb01183.x
Subject(s) - escherichia coli , ribosome , dissociation (chemistry) , chemistry , biophysics , biochemistry , biology , rna , organic chemistry , gene
1 Mg 2+ ‐dependent dissociation of Escherichia coli ribosomes has been studied at various Mg 2+ concentrations ranging from 10 to 0.5 mM. The extent of dissociation was determined by sucrose gradient centrifugation. 2 Of all 70 S ribosomes present in standard iS30 extracts about 50% dissociate in a relatively narrow range of Mg 2+ concentration (between 4 and 2 mM), whereas the remainder dissociate between 10 and 4 mM Mg 2+ . 3 Puromycin at a concentration (0.1 mg/ml) which releases about 90% of nascent polypeptide chains after polypeptide synthesis does not influence the Mg 2+ ‐dependent dissociation curve of iS30 ribosomes, whereas it has a significant effect on the dissociation of 70 S ribosomes bearing peptidyl‐tRNA (so called complexed 70 S ribosomes). Very high concentrations of puromycin (1 mg/ml) in addition to chain release also cause dissociation of ribosomes at 10 mM Mg 2+ . 4 Twenty‐five per cent of the complexed 70 S particles, isolated after MS 2 ‐RNA programmed polypeptide synthesis, dissociate between 4 and 2 mM Mg 2+ . The remainder 75% dissociate between 2 and 0.5 mM Mg 2+ . 5 The distribution of the various classes of free and complexed 70 S ribosomes in iS30 extracts before and after MS 2 ‐RNA directed polypeptide synthesis and before and after puromycin action has been determined.