Involvement of ABC transporter genes slnTI and slnTII in salinomycin biosynthesis

Abstract:

[Objective] In the salinomycin biosynthetic gene cluster, slnTI and slnTII encode the ABC transporter ATP-binding subunit and trans-membrane subunit, respectively. We speculate that slnTI and slnTII are most likely related to salinomycin export. Here, the role of slnTI and slnTII on salinomycin biosynthesis and resistance was investigated by gene replacement and overexpression. [Methods] Using REDIRECT? technology, the slnTI mutant LJ01 and the slnTII mutant LJ02 were constructed, and further verified by trans-complementation with cloned corresponding genes. SlnTI and SlnTII were overexpressed in the wild-type Streptomyces albus XM211. Also, slnTI and slnTII were introduced into S. lividans 1326, and the resistance to salinomycin of the resulted strains was tested. [Results] Compared with the wild-type strain, salinomycin production in LJ01 and LJ02 decreased by 27.2% and 45.4%, respectively. The transcription of structure gene slnA3 and regulatory gene slnR were both reduced in LJ01 and LJ02. The overexpression of slnTI and slnTII in the wild-type XM211 resulted in a 14.6% enhanced salinomycin production. Correspondingly, the transcription of slnA3 and slnR was also increased. Additionally, heterologous expression of slnTI and slnTII in S. lividans 1326 slightly increased its resistance to salinomycin. [Conclusion] slnTI and slnTII are identified to be related to the production of salinomycin, but not to be the main resistant gene for salinomycin in the producer.