The heterogeneity of undermodified
phenylalanine tRNA produced in relaxed control E. coli during
amino acid starvation was investigated. Examination of the RPC-5 elution profiles of
tRNAPhe prepared from non-starved cells and cells starved of a variety of
amino acids, including some known to be involved in the formation of modified bases revealed that: (1) only one species of fully modified
tRNAPhe appears to occur in cells grown in enriched medium; (2) at least two chromatographically unique isoacceptor species are observed in addition to the normal
tRNAPhe in starved cells; (3) the unique, undermodified species of
tRNAPhe from
leucine-starved cells, known to be deficient in dihydrouridine,
pseudouridine, 2-thiomethyl-N6-(delta2-isopentenyl)
adenosine and 3-(3-amino-3-carboxypropyl)
uridine, co-elute with the unique species produced in cells starved of
histidine or
arginine or treated with
puromycin or
chloramphenicol; (4) additional unique species of
tRNAPhe can be detected in methyl- and
sulfur-deficient
tRNA from
methionine- and
cysteine-starved cells; (5) analysis of phenoxyacetylated
tRNA revealed that the chromatographically unique and normal species from starved cells contain subspecies deficient in 3-(3-amino-3-carboxypropyl)
uridine; and (6) using phenoxyacetylation as a means of effecting the resolution of undermodified subspecies, a total of at least ten chromatographically unique subspecies of rRNAPhe were detected in an organism that appears to posses only one gene for
tRNAPhe. Taken together, the results support the view that there are both general and specific effects of
amino acid starvation on the post-transcriptional modification of
tRNA.