A Study of Codon‐Dependent Binding of Aminoacyl‐tRNA with the Ribosomal 30‐S Subparticle of Escherichia coli

Publisher Website
Google Scholar
Abstract
Titration of isolated Escherichia coli ribosomal 30‐S particles with [14C]phenylalanyl‐tRNA in the presence of poly(uridy1ic acid) was used for a quantitative assay of codon‐dependent binding of aminoacyl‐tRNA with the small ribosomal subparticle. The technique has allowed the estimation both of the fraction of “active” 30‐S subparticles capable of forming the 30‐S · poly(U) · phenylalanyl‐tRNA complexes and the equilibrium constants of phenylalanyl‐tRNA binding in different media.Heterogeneity of the ternary complexes formed has been revealed: at least two classes of complexes differing in stability have been observed.The stability of the 30‐S · poly(U) · phenylalanyl‐tRNA complexes has been shown to decrease with the lowering of the Mg2+ concentration, the increase of K + concentration and the addition of urea. The stability of the complexes increases with the increase of Mg2+ concentration, with the addition of ethanol and decrease of temperature.It is demonstrated that the fraction of actively binding 30‐S particles also varies in different medium conditions; it decreases with the increase of ionic strength (K +) and with the addition of urea, and increases with the increase of Mg2+ concentration and addition of ethanol.