SUMMARY: Determinants of tetracycline resistance have been cloned from two different tetracycline-producing industrial strains of into using the plasmid vector pUT206. Three plasmids, pUT250 and pUT260 with a 9.5 and a 7.5 kb insert respectively of DNA, and pUT270 with a 14.0 kb insert of DNA, conferring resistance to tetracycline, have been isolated. By sub-cloning, a similar fragment of 2.45 kb containing the tetracycline resistance gene () was further localized on these plasmids. The gene has been cloned into and expressed under the control of λpL or Lpp promoters. Differential protein extraction of cells revealed the presence of an additional membrane-embedded protein in tetracycline-resistant cells. On the basis of available restriction endonuclease maps, the 347 gene is probably identical to the gene from recently identified by T. Ohnuki and co-workers as responsible for the reduced accumulation of tetracycline. The nucleotide sequence of a 2052 bp DNA fragment containing the Tc structural gene from has been determined. The amino acid sequence of the 347 protein ( 35818) deduced from the nucleotide sequence shows a limited but significant homology to other characterized tetracycline transport acting determinants from pathogenic bacteria.


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