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Gene. 1991 Jan 2;97(1):137-42.

Cloning of tlrD, a fourth resistance gene, from the tylosin producer, Streptomyces fradiae.

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Department of Biochemistry, University of Leicester, U.K.


In addition to tlrA, tlrB and tlrC, which were previously cloned by others, a fourth antibiotic-resistance gene (tlrD) has been isolated from Streptomyces fradiae, a producer of tylosin (Ty), and cloned in Streptomyces lividans. Like tlrA, tlrD encodes an enzyme that methylates the N6-amino group of the A2058 nucleoside within 23S ribosomal RNA. However, whereas the tlrA protein dimethylates that nucleoside, the tlrD product generates N6-monomethyladenosine. The genes also differ in their mode of expression: tlrA is inducible, whereas tlrD is apparently expressed constitutively, and it has been confirmed that the tlrA-encoded enzyme can add a second methyl group to 23S rRNA that has already been monomethylated by the tlrD-encoded enzyme. Presumably, that is what happens in S. fradiae.

[Indexed for MEDLINE]

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