Molecular analysis of tlrB, an antibiotic-resistance gene from tylosin-producing Streptomyces fradiae, and discovery of a novel resistance mechanism

The tlrB gene. which confers inducible resistance to a range of macrolide a ntibiotics including biosynthetic precursors of tylosin, was isolated and s equenced. In the genome of Streptomyces fradiae it lies between pbp, which encodes a putative penicillin-binding protein, and tylN, encoding a glycosy ltransferase involved in tylosin biosynthesis. The TlrB protein was produce d in E. coli as a fusion to MalE. The fusion protein, but not MalE alone, i nactivates macrolides in the presence of S-adenosyl-methionine (SAM) but th e modified product(s) has not been characterised.