Coding properties of two conformations of tryptophanyl-tRNA in Escherichia coli

Abstract

Coding properties of the two conformations of Escherichia coli B tryptophan tRNA were examined. Form I was bound to ribosomes in response to UGG and poly UG, but not to poly AC. Form II did not respond to poly UG, but was bound to poly AC both in the presence and absence of ribosomes at pH 7.2. Form II did not respond to triplet codon composed of A and C in the presence of ribosomes. Form II binding to poly AC in the absence of ribosomes was completely eliminated when assayed at pH 7.8. At pH 7.2 and pH 7.8, form II showed a high level of binding to ribosomes in the absence of polymer. The binding of form II to ribosomes, however, was eliminated by poly U or poly UG, but enhanced by poly AC. Form I participated in in vitro polypeptide synthesis directed by poly UG. Tryptophan from form II was not incorporated into polypeptide in response to either poly UG or poly AC at either pH 7.2 or pH 7.8. These results indicate that the code response of form I is normal while that of form II is abnormal.