Tryptophan tRNA of Escherichia coli

Abstract

THE tryptophan tRNA of CAJ64, a UGA suppressing strain of Escherichia coli¹, has an altered structure compared with that isolated from the wild type (CA244). A complete account of this work will be published elsewhere, but the sequence shown in Fig. 1 has two points of immediate interest. First, both the su⁺ and su⁻ structures contain an adenosine at position 15 and a uridine at position 48. In most other tRNAs guanosine and cytosine, respectively, occupy homologous positions in the sequence. Another exception with adenosine and uridine in these positions has recently been found in a leucine tRNA of E. coli². The three dimensional model proposed by Levitt³ has hydrogen bonds between the bases in these positions; these coordinate base changes are consistent with the structure and lend support to this feature of it.