Mechanismen der Proteinsynthese, III. Über einige Aktivitäten hochgereinigter Ribosomen vonEscherichia coli

Abstract

A method for preparing relatively stable 30S and 50S-subunits from 3 times NH4C1 washed ribosomes of E. coli is described and the properties of these particles are characterized by aminoacyl-tRNA-binding, poly-peptide synthesis and sedimentation. In poly-U-dependent binding of Phe-tRNA to ribosomes, Mn2ffl and Ca2 can fully replace Mg2[image]. Ammonium chloride-washing strongly reduces the capacity to bind FMet-tRNA coded by poly A, U, G. With 3 times standard buffer-washed ribosome-preparations, the binding optima for FMet-tRNAFMet(4mM) and Met-tRNAMet( 16mM) can mutually exclude binding of the other methionineadapter. The same 2 optima are found for the mixture of non-formylated Met-tRNA''s. The Mg2[image]-optima for binding Met-tRNAMeti Phe-, and Tyr-tRNA are similar; K[image], however, apparently stimulates the sorption of FMet-tRNAFMet(+ 134%) more than the binding of non-formylated Met-tRNAFMet (+ 34%). Possible explanations involving 2 ribosomal sites for binding aminoacyl-tRNA and FMet-tRNA or alternatively modification of the 1 site by Mg2[image] concentration are briefly discussed.