Kinetic studies on the interaction of chain initiation factor 3 with 70 S Escherichia coli ribosomes and subunits

D. J. Goss, Lawrence J Parkhurst, A. J. Wahba

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24 Scopus citations


The magnesium ion dependencies of several of the reaction rates for assembly of the E. coli protein synthesis initiation complex have been determined as the effects of IF-3 (initiation factor 3) on the overall reaction of 30 S and 50 S ribosomal subunits. The reaction kinetics were studied by light-scattering changes as well as by changes in the fluorescence anisotropy of dansylated-IF-3. The full model for treating these processes consists of 4 reactions, 3 of which are thermodynamically independent. Conditions were chosen and techniques were employed that allowed three of the reactions to be studied individually. This allowed the authors to fit, with a single adjustable rate constant, all of the light-scattering changes that occurred upon flowing 30 S and 50 S ribosomal subunits against varying concentrations of both Mg2+ and IF-3. Preparations of IF-3 were found to react toward 30 S subunits with either of two markedly different binding rates. The authors find that the simplest model that explains both the light-scattering and anisotoropy data for all IF-3 experiments is one that includes as a necessary step the association of 30 S-IF-3 with 50 S subunits to form a 70 S-IF-3 complex.

Original languageEnglish (US)
Pages (from-to)10119-10127
Number of pages9
JournalJournal of Biological Chemistry
Issue number17
Publication statusPublished - Dec 1 1982


ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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