Open AccessThe Role of Ribosomal Conformation in Protein Biosynthesis
Author(s) -
Sherman Michael I.
Publication year - 1972
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1972.tb01696.x
Subject(s) - ribosome , ribosomal rna , streptomycin , protein biosynthesis , phenylalanine , 30s , isoleucine , 50s , ribosomal protein , tritium , chemistry , translation (biology) , biochemistry , leucine , biology , biophysics , rna , amino acid , messenger rna , physics , antibiotics , nuclear physics , gene
Hydrogen‐tritium exchange studies on ribosomes and poly(U)‐directed protein synthesis assays have been carried out at 12°C in the absence and presence of a wide spectrum of streptomycin concentrations. At very low (“catalytic”) streptomycin/ribosome, ratios, the ribosomal hydrogen‐tritium exchange rate is increased; this “loosening” phase is characterized functionally by a slight but reproducible inhibition of the incorportion of phenylalanine, and often of leucine and isoleucine, into polypeptide. At higher streptomycin/ribosome ratios, the exchange rate is decreased. This “tightening” of structure correlates with the onset of miscoding. The “loosening” and “tightening” phases appear to represent different ribosomal conformations with qualitatively different effects upon ribosomal function. This in turn suggests that there is more than one type of binding site for streptomycin on the ribosome, not inconsistent with the results of binding studies. Evidence is also provided suggesting that streptomycin interferes with initiation in the poly(U) system, although ribosomes are not irreversibly inactivated by streptomycin. The bearing of our results upon the phenomenon of phenotypic suppression is discussed.