title: The cmbT gene encodes a novel major facilitator multidrug resistance transporter in Lactococcus lactis.
abstract: Functional characterization of the multidrug resistance CmbT transporter was performed in Lactococcus lactis. The cmbT gene is predicted to encode an efflux protein homologous to the multidrug resistance major facilitator superfamily. The cmbT gene (1377 bp) was cloned and overexpressed in L. lactis NZ9000. Results from cell growth studies revealed that the CmbT protein has an effect on host cell resistance to lincomycin, cholate, sulbactam, ethidium bromide, Hoechst 33342, sulfadiazine, streptomycin, rifampicin, puromycin and sulfametoxazole. Moreover, in vivo transport assays showed that overexpressed CmbT-mediated extrusion of ethidium bromide and Hoechst 33342 was higher than in the control L. lactis NZ9000 strain. CmbT-mediated extrusion of Hoechst 33342 was inhibited by the ionophores nigericin and valinomycin known to dissipate proton motive force. This indicates that CmbT-mediated extrusion is based on a drug-proton antiport mechanism. Taking together results obtained in this study, it can be concluded that CmbT is a novel major facilitator multidrug resistance transporter candidate in L. lactis, with a possible signaling role in sulfur metabolism.
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11010 Belgrade, Serbia. brankicaf@pharmacy.bg.ac.rs
authors.forename: Brankica
authors.initials: B
authors.lastname: Filipic
authors.forename: Natasa
authors.initials: N
authors.lastname: Golic
authors.forename: Branko
authors.initials: B
authors.lastname: Jovcic
authors.forename: Maja
authors.initials: M
authors.lastname: Tolinacki
authors.forename: Denice C
authors.initials: DC
authors.lastname: Bay
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Turner
authors.forename: Jelena
authors.initials: J
authors.lastname: Antic-Stankovic
authors.forename: Milan
authors.initials: M
authors.lastname: Kojic
authors.forename: Ljubisa
authors.initials: L
authors.lastname: Topisirovic
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D015870:Gene Expression; D013294:Lactococcus lactis / Q000235:genetics* / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C443980:CmbT protein, Lactococcus lactis; D026901:Membrane Transport Proteins; D011994:Recombinant Proteins; D013455:Sulfur