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The AcrA/AcrB/TolC complex spans the inner and outer membranes of Escherichia coli and serves as its major drug-resistance pump. Driven by the proton motive force, it mediates the efflux of bile salts, detergents, organic solvents, and many structurally unrelated antibiotics. Here, we report a crystallographic structure of trimeric AcrB determined at 2.9(More)
Under anoxic conditions in the presence of an oxidizable cosubstrate such as glucose or glycerol, Escherichia coli converts citrate to acetate and succinate. Two enzymes are specifically required for the fermentation of the tricarboxylic acid, i.e., a citrate uptake system and citrate lyase. Here we report that the open reading frame (designated citT)(More)
AcrAB-TolC is the major efflux protein complex in Escherichia coli extruding a vast variety of antimicrobial agents from the cell. The inner membrane component AcrB is a homotrimer, and it has been postulated that the monomers cycle consecutively through three conformational stages designated loose (L), tight (T), and open (O) in a concerted fashion.(More)
Basolateral efflux is a necessary step in transepithelial (re)absorption of amino acids from small intestine and kidney proximal tubule. The best characterized basolateral amino acid transporters are y+LAT1-4F2hc and LAT2-4F2hc that function as obligatory exchangers and thus, do not contribute to net amino acid (re)absorption. The aromatic amino acid(More)
The sodium-ion-dependent citrate carrier of Klebsiella pneumoniae (CitS) was purified and reconstituted into liposomes to investigate the properties of this transport system without interference from other proteins. Citrate uptake was an electroneutral process, where delta pNa+ and/or delta pH are driving forces. Delta psi was unable to stimulate citrate(More)
The sodium-ion-dependent citrate carrier of Klebsiella pneumoniae (CitS) was purified by means of bioengineerical methods. By fusing the biotin acceptor domain of the alpha-subunit of the oxaloacetate decarboxylase of K. pneumoniae to the C-terminus of CitS, purification of the carrier was achieved by use of a monomeric avidin-Sepharose column.(More)
Antimicrobial resistance of human pathogenic bacteria is an emerging problem for global public health. This resistance is often associated with the overproduction of membrane transport proteins that are capable to pump chemotherapeutics, antibiotics, detergents, dyes and organic solvents out of the cell. In Gram-negative bacteria such as Escherichia coli(More)
The Escherichia coli multidrug efflux pump protein AcrB has recently been cocrystallized with various substrates, suggesting that there is a phenylalanine-rich binding site around F178 and F615. We found that F610A was the point mutation that had the most significant impact on substrate MICs, while other targeted mutations, including conversion of(More)
BACKGROUND & AIMS Hartnup amino acid transporter B(0)AT1 (SLC6A19) is the major luminal sodium-dependent neutral amino acid transporter of small intestine and kidney proximal tubule. The expression of B(0)AT1 in kidney was recently shown to depend on its association with collectrin (Tmem27), a protein homologous to the membrane-anchoring domain of(More)
The rate of amino acid efflux from individual cells needs to be adapted to cellular demands and plays a central role for the control of extracellular amino acid homeostasis. A particular example of such an outward amino acid transport is the basolateral efflux from transporting epithelial cells located in the small intestine and kidney proximal tubule.(More)