Premium
An ABC‐transporter from Streptomyces longisporoflavus confers resistance to the polyether‐ionophore antibiotic tetronasin
Author(s) -
Linton Kenneth J.,
Cooper Howard N.,
Hunter Lain S.,
Leadlay Peter F.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00355.x
Subject(s) - biology , streptomyces , atp binding cassette transporter , efflux , streptomyces albus , subcloning , antiporter , orfs , biochemistry , transmembrane domain , transmembrane protein , streptomycetaceae , gene , open reading frame , genetics , transporter , peptide sequence , bacteria , actinomycetales , plasmid , membrane , receptor
Summary Streptomyces longisporoflavus produces the poly‐ketide‐polyether antibiotic, tetronasin, which acts as an ionophore and depolarizes the membrane of bacteria sensitive to the drug. A genomic library of S. longisporoflavus DN A was cloned in Streptomyces Uvldans and screened to identify tetronasin‐resistance determinants. The inclusion of 0.2 M NaCl in the growth medium with tetronasin markedly improved the sensitivity of the screen. Two different resistance determinants, designated tnrB (ptetR51) and tnrA (ptetR11) respectively, were identified. The determinant tnrB (ptetR51) but not tnrA (ptetR11), also conferred resistance to tetronasin when cloned into Streptomyces albus. The tnrB determinant was further localized, by subcloning, to a 2.8 kb Kpnl fragment. DNA sequence analysis of this insert revealed one incomplete and two complete open reading frames (ORFs 1, 2 and 3). The deduced sequence of the gene product of ORF2 (TnrB2) revealed significant similarity to the ATP‐binding domains of the ABC ( A TP b inding c assette) superfamily of transport‐related proteins. The adjacent gene, ORF3, is translationally coupled to ORF2 and would encode a hydrophobic protein (TnrB3) with six transmembrane helices which probably constitutes the integral membrane component of the transporter. The mechanism of tetronasin resistance mediated by tnrB is probably an ATP‐dependent efflux system.