Analysis of the complete nucleotide sequence of the tetracycline resistance transposon Tn10

An analysis of the complete nucleotide sequence of the composite tetracycli ne-resistance transposon Tn10 (9137 bp) from the Salmonella typhi conjugati ve plasmid R27 is presented. A comparison of the protein sequences from IS1 0-right and IS10-left transposases has identified four amino acid differenc es. These residues appear to play an important role in normal transposase f unction and may account for the differences in exhibited transposition acti vities. The tetracycline determinants encoded by this version of Tn10 share >99% identity with those of TnI0(R100), demonstrating the conservation tha t exists between these transposons. A previously uncharacterized similar to 3000-bp region of Tn10 contains four putative open reading frames. One of these open reading frames shares 55% identity with the glutamate permease p rotein sequence from Haemophilus influenzae although it was unable to compl ement an Escherichia coli glutamate permease mutant, with which it shares 5 1% identity. The three remaining putative open reading frames are arranged as a discrete generic unit adjacent to the glutamate permease homolog and a re transcribed in the opposite direction. Two of these open reading frames are homologous with Bacillus subtilis proteins of unknown functions while t he other has no homologs in the database. The presence of an aminoacyl-tRNA synthetase class II motif in one of these open reading frames in combinati on with the glutamate permease homolog allows us to postulate that this reg ion of Tn10 could once have played a role in amino acid metabolism. (C) 200 0 Academic Press.