Previously, we reported that
starvation of Rel Escherichia coli for
methionine, but not
leucine or
histidine, results in chromatographically unique species of aspartyl-specific transfer
ribonucleic acid (
tRNAAsp) lacking the modified
nucleoside Q. The present studies demonstrate that
methionine starvation of Rel+ E. coli yields a qualitatively similar, but less pronounced, effect. Furthermore, during recovery from
methionine starvation in Rel E. coli, the chromatographic elution pattern of
tRNAAsp shifts towards that observed for unstarved cells after 1 h of recovery, and the shift appears complete after 2 h of recovery. This shift is inhibited by
rifampin. Incorporation of [2-14C]
methionine or [methyl-3H]
methionine into growing cells of E. coli does not result in labeling of
nucleoside Q. We interpret these findings to indicate that
methionine has an indirect role in Q formation and that Q-deficient
tRNA can be modified slowly to contain Q but that transcription is required. The chromatographic elution patterns of
tRNAAsp from Rel E. coli starved for
arginine, lysine, or
glutamic acid indicate that these
amino acids are not the source of the three- or five-
carbon sequences in the modified portion of Q.