Identification of two lysine tRNA cistrons in Bacillus subtilis by hybridization of lysyl-tRNA with DNA

Post-transcriptional modifications of the anticodon loop region: alterations in isoaccepting species of tRNA's during development in Bacillus subtilis

Structural similarities of tRNA's were compared using three sets of isoaccepting species that had previously been shown to undergo significant changes in chromatographic elution properties as a function of developmental stage in Bacillus subtilis. Comparisons of the structures of the tRNA's were based on the composition of their modified nucleosides, comparisons of oligonucleotide elution profiles from RPC-5 columns, and two-dimensional electrophoretic fingerprint analysis of oligonucleotides. The tRNA's studied were tRNA(Lys) (1) and tRNA(Lys) (3); tRNA(Tyr) (1) and tRNA(Tyr) (2); and tRNA(Trp) (1) and tRNA(Trp) (2). The results suggest that the difference among these pairs of isoaccepting species is a difference in the degree of post-transcriptional modifications of the anticodon loop region. The nucleosides involved were N(6)-(Delta(2)-isopentenyl)adenosine (i(6)A), 2-methylthio-N(6)-(Delta(2)-isopentenyl)adenosine (ms(2)i(6)A), and an unknown nucleoside K, which occurred in a position analogous to N-[9-(beta-d-ribofuranosyl)purin-6-ylcarbamoyl]threonine. The amounts of i(6)A and ms(2)i(6)A, determined using total tRNA from exponential-or stationary-phase cells, suggest that the thiomethylation of i(6)A is a pleiotropic phenomenon affecting several tRNA species. As opposed to the situation in Escherichia coli tRNA, where ms(2)i(6)A constitutes about 90% of the total hydrophobic nucleosides at all growth stages, B. subtilis tRNA's have i(6)A as the predominant hydrophobic nucleoside in exponential growth and ms(2)i(6)A as the predominant nucleoside in stationary phase. Thus, the enzyme system which forms i(6)A and the enzyme system which thiomethylates i(6)A are not coordinated during growth in B. subtilis as they are in E. coli. It is suggested that these changes in anticodon loop modifications in B. subtilis may be related to changes in the translational apparatus which occur during sporulation.

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

A reversal in the relative amounts of the two major species of tyrosine transfer ribonucleic acid (tRNATyr) (I and II) has been previously observed by others during the development of Bacillus 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 tRNATyr 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, tRNATyr change is iron dependent. Moreover, when sporulation is prevented by an excess of glucose, the tRNATyr change is delayed as is the synthesis of enzymatic systems required for the onset of sporulation. tRNATyr change also demands unceasing protein synthesis.

Analysis of isoaccepting transfer ribonucleic acid species of Bacillus subtilis: chromatographic differences between transfer ribonucleic acids from spores and cells in exponential growth

Differences between the transfer ribonucleic acid (tRNA) of spores and exponentially growing cells of Bacillus subtilis 168 were compared by co-chromatography on reversed-phase column RPC-5. This system gave excellent resolution of isoaccepting species in 1 to 2 hr using a 200-ml gradient. Two methods were used to extract spore tRNAs, a procedure using a Braun homogenizer and a pretreatment with dithiothreitol followed by lysis with lysozyme. Where changes were observed, column elution profiles of spore tRNAs were independent of the extraction method used. Three kinds of changes between the profiles of vegetative cell tRNA and spore tRNA were observed: (i) no change; phe-, val-, ala-, asp-, ileu-, pro-, met-, fmet-, and his-tRNAs, (ii) a change in the ratio of existing peaks; gly-, tyr-, leu-, ser-, thr-, aspn-, and arg-tRNAs, and (iii) the appearance or disappearance of unique peaks; lys-, glu-, and trp-tRNAs.