The nucleotide sequence of a plasmid determinant for resistance to tellurium anions

The plasmid pMJ606 contains a 5-kb insert specifying resistance to tellurium salts (TeR) which was cloned from the large conjugative plasmid pMER610. Nucleotide sequence analysis of this insert has identified five open reading frames (ORFs). ORFs 1, 2, 4 and 5 correspond in terms of their predicted polypeptide products to the 41, 15.5, 22 and 23-kDa polypeptides, respectively, which are synthesised by the resistance determinant in maxicells. An additional ORF, ORF3, whose product has not been identified is predicted by the sequence data. The sequence of the presumptive polypeptide specified by ORF3 indicates a membrane location. The nucleotide and predicted amino acid sequences of ORF4 and ORF5 show considerable homology which is consistent with the duplication and minor divergence of an ancestral gene. ORFs 4 and 5 appear to retain the same function and while each can function separately and contribute to the resistance mechanism, the full level of wild-type resistance requires both genes to function. The transcriptional signals for the TeR determinant may be located beyond and 5' of the sequences cloned in pMJ606.