Affiliation:
1. Biomedical Research Department, SRI International, Menlo Park, California 94025
Abstract
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
-(Δ
2
-isopentenyl)adenosine (i
6
A), 2-methylthio-
N
6
-(Δ
2
-isopentenyl)adenosine (ms
2
i
6
A), and an unknown nucleoside K, which occurred in a position analogous to
N
-[9-(β-
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference14 articles.
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5. Identification of two Iysine tRNA cistrons in Bacillus subtilis by hybridization of Iysyl-tRNA with DNA;Chuang R.;Biochem. Biophys. Res. Commun.,1971
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