Studies on genetically altered transfer RNA species in Escherichia coli.

The study of tRNA molecules altered by a mutational event can lead to information in 3 important areas: (a) structure-function relationships in tRNA biochemistry; (ft) the genetics of tRNA; and (c) the physiological role of tRNA-isoaccepting species. For example, the elucidation of the structural alteration in a mutant tRNA species which reacts appreciably more slowly than normal tRNA in the enzyme-catalyzed aminoacylation reaction could give valuable information on the tRNA structural parameters vital to this reaction. With regard to the 2nd point, the genetic mapping of tRNA mutants can yield information on the relative location and number of copies of the genes specifying the isoaccepting species of a tRNA (3, 8). Finally, cells carrying a mutation that inactivates or alters a normal tRNA subspecies frequently show pronounced physiological effects due to the absence of the normal tRNA function (4,9). Thus, possible regulatory or nontranslational functions of tRNA subspecies could be investigated. This paper summarizes the work carried out in our laboratories during the past few years on mutationally altered, glycine-specific tRNA's in Escherichia coli.