Abstract
Escherichia coli produces the iron-chelating compound enterobactin to enable growth under iron-limiting conditions. After biosynthesis, enterobactin is released from the cell. However, the enterobactin export system is not fully understood. Previous studies have suggested that the outer membrane channel TolC is involved in enterobactin export. There are several multidrug efflux transporters belonging to resistance-nodulation-cell division (RND) family that require interaction with TolC to function. Therefore, several RND transporters may be responsible for enterobactin export. In this study, we investigated whether RND transporters are involved in enterobactin export using deletion mutants of multidrug transporters in E. coli. Single deletions of acrB, acrD, mdtABC, acrEF, or mdtEF did not affect the ability of E. coli to excrete enterobactin, whereas deletion of tolC did affect enterobactin export. We found that multiple deletion of acrB, acrD, and mdtABC resulted in a significant decrease in enterobactin export and that plasmids carrying the acrAB, acrD, or mdtABC genes restored the decrease in enterobactin export exhibited by the ΔacrB acrD mdtABC mutant. These results indicate that AcrB, AcrD, and MdtABC are required for the secretion of enterobactin.
Highlights
Multidrug efflux transporters cause serious problems in cancer chemotherapy and in the treatment of bacterial infections
TolC is required for enterobactin export Bleuel et al have shown that TolC is involved in the efflux of enterobactin across the outer membrane of E. coli [30]
Effect of deletion of individual TolC-dependent drug efflux genes and entS on enterobactin release To investigate the role of the TolC-dependent resistancenodulation-cell division (RND)-type drug efflux systems on the release of enterobactin from E. coli, we performed RP high-performance liquid chromatography (HPLC) analysis of the culture supernatants from cultures of E. coli MG1655 mutants containing single deletions of the acrB, acrD, mdtABC, acrEF, and mdtEF genes
Summary
Multidrug efflux transporters cause serious problems in cancer chemotherapy and in the treatment of bacterial infections. In gram-negative bacteria, transporters belonging to the resistancenodulation-cell division (RND) family are effective in generating resistance because they form a tripartite complex with periplasmic proteins and an outer membrane protein channel. The AcrAB–TolC system is composed of the RND transporter AcrB, membrane fusion protein AcrA, and multifunctional outer membrane channel TolC. It has been suggested that the AcrAB–TolC multidrug efflux system is capable of capturing substrates in the periplasm rather than in the membrane or the cytoplasm [2]. This claim is supported by high-resolution structures of AcrB, in which access pathways from the periplasm, but not from the cytoplasm, have been identified [3,4]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
