Study of tyrosine transfer ribonucleic acid modification in relation to sporulation in Bacillus subtilis

Abstract

A reversal in the relative amounts of the two major species of tyrosine transfer ribonucleic acid (tRNA(Tyr)) (I and II) has been previously observed by others during the development of B. subtilis. These species have been purified by benzoylated diethylaminoethyl cellulose chromatography and were shown to differ by the modification of an adenosine residue (species I contains i6A and species II ms2i6A). As suggested by competitive hybridization assays, they might possess the same nucleotide sequence. A tRNA(Tyr) species lacking isopentenyl and methylthio moieties was not detected. The structural difference between species I and II was shown to be important for ribosome binding but not for charging. The extent of alteration during growth was studied in parallel with physiological events. Like sporulation, tRNA(Tyr) change is iron dependent. Moreover, when sporulation is prevented by an excess of glucose, the tRNA(Tyr) change is delayed as in the synthesis of enzymatic systems required for the onset of sporulation. tRNA(Tyr) change also demands unceasing protein synthesis.