Organization and copy number of initiator tRNA genes in slow- and fast-growing mycobacteria |
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Authors: | M Vasanthakrishna N Rumpal U Varshney |
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Institution: | (1) Department of Microbiology and Cell Biology, Indian Institute of Science, 560 012 Bangalore, India |
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Abstract: | We have previously reported the isolation and characterization of a functional initiator tRNA gene,metA, and a second initiator tRNA-like sequence,metB, fromMycobacterium tuberculosis. Here we describe the fine mapping of the initiator tRNA gene locus of the avirulent (H37Ra) and virulent (H37Rv) strains
ofM. tuberculosis. The genomic blot analyses show that the 1.7 kb (harbouringmetE) and the 6.0 kb BamHI (harbouringmetA) fragments are linked. Further, sequencing of a portion of the 6.0kb fragment, in conjunction with the sequence of the 1.7
kb fragment confirmed the presence of an IS6110 element in the vicinity ofmetB. The IS element is flanked by inverted (28 bp, with 3 contiguous mismatches in the middle) and direct (3 bp) repeats considered
to be the hallmarks of IS6110 integration sites. The organization of the initiator tRNA gene locus is identical in both the
H37Ra and H37Rv strains and they carry a single copy of the functional initiator tRNA gene. Interestingly, the fast growingMycobacterium smegmatis also bears a single initiator tRNA gene. This finding is significant in view of the qualitative differences in total tRNA
pools and the copy number of rRNA genes in the fast- and slow-growing mycobacteria. Finally, we discuss hypotheses related
to the origin ofmetB inM. tuberculosis. |
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Keywords: | metA metB 1S6110 integrative elements |
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