A bacterial antibiotic-resistance gene that complements the human multidrug-resistance P-glycoprotein gene

Abstract

Bacteria have developed many fascinating antibiotic-resistance mechanisms. A protein in Lactococcus lactis, LmrA, mediates antibiotic resistance by extruding amphiphilic compounds from the inner leaflet of the cytoplasmic membrane. Unlike other known bacterial multidrug-resistance proteins, LmrA is an ATP-binding cassette (ABC) transporter. The human multidrug-resistance P-glycoprotein, encoded by the MDR1 gene, is also an ABC transporter, overexpression of which is one of the principal causes of resistance of human cancers to chemotherapy. We expressed lmrA in human lung fibroblast cells. Surprisingly, LmrA was targeted to the plasma membrane and conferred typical multidrug resistance on these human cells. The pharmacological characteristics of LmrA and P-glycoprotein-expressing lung fibroblasts were very similar, and the affinities of both proteins for vinblastine and magnesium-ATP were indistinguishable. Blockers of P-glycoprotein-mediated multidrug resistance also inhibited LmrA-dependent drug resistance. Kinetic analysis of drug dissociation from LmrA expressed in plasma membranes of insect cells revealed the presence of two allosterically linked drug-binding sites indistinguishable from those of P-glycoprotein. These findings have implications for the reversal of antibiotic resistance in pathogenic microorganisms. Taken together, they demonstrate that bacterial LmrA and human P-glycoprotein are functionally interchangeable and that this type of multidrug-resistance efflux pump is conserved from bacteria to man.

Sterol Transport by the Human Breast Cancer Resistance Protein (ABCG2) Expressed in Lactococcus lactis

“…The localization of BCRP suggests that it could have a potential role in protection against toxins. The recent observation in BCRP knock-out mice that BCRP protects against a chlorophyll-derived dietary phototoxin and protoporphyria is consistent with this notion (20).Previously, we have characterized the molecular basis of the drug specificity of LmrA, a half-transporter homologue of human P-glycoprotein MDR1, in the Gram-positive bacterium Lactococcus lactis (21,22). To allow a detailed comparison of BCRP and LmrA, human BCRP was functionally expressed in L. lactis using the nisin A-induced expression system that is used for the expression of LmrA.…”

“…Previously, we have characterized the molecular basis of the drug specificity of LmrA, a half-transporter homologue of human P-glycoprotein MDR1, in the Gram-positive bacterium Lactococcus lactis (21,22). To allow a detailed comparison of BCRP and LmrA, human BCRP was functionally expressed in L. lactis using the nisin A-induced expression system that is used for the expression of LmrA.…”

ATPase Activity of the MsbA Lipid Flippase of Escherichia coli

“…Our genetic evidence strongly suggests that MsbA functions as a general lipid transporter, or flippase, playing a key role in the movement of lipids from the inner membrane to the outer membrane of E. coli (11). Although there is no evidence that MsbA confers multidrug resistance in E. coli, the related LmrA protein of Lactococcus lactis does in fact confer resistance to many of the same amphiphilic compounds that are transported by MDR1 (16,17).…”

Investigating transport proteins by solid state NMR

“…It forms a homodimer of two 64 kDa subunits each containing 6 transmembrane helices and one nucleotide binding domain. It has been shown to be a functional homologue of the human P-glycoprotein (van Veen et al 1998). Substrates of both proteins accumulate within the membrane in the interface region as shown by 1 H-MAS NMR (Siarheyeva et al , submitted).…”