Pyridylpiperazine-based allosteric inhibitors of RND-type multidrug efflux pumps.

Efflux transporters of the RND family confer resistance to multiple antibiotics in Gram-negative bacteria. Here, we identify and chemically optimize pyridylpiperazine-based compounds that potentiate antibiotic activity in E. coli through inhibition of its primary RND transporter, AcrAB-TolC.

Binding of Tetracyclines to TetR Involves Two Arginines as Specificity Determinants.

is an important nosocomial pathogen that requires thoughtful consideration in the antibiotic prescription strategy due to its multidrug resistant phenotype. Tetracycline antibiotics have recently been re-administered as part of the combination antimicrobial regimens to treat infections caused by . We show that the TetA(G) efflux pump of AYE confers resistance to a variety of tetracyclines including the clinically important antibiotics doxycycline and minocycline, but not to tigecycline.

Allosteric drug transport mechanism of multidrug transporter AcrB.

Gram-negative bacteria maintain an intrinsic resistance mechanism against entry of noxious compounds by utilizing highly efficient efflux pumps. The E. coli AcrAB-TolC drug efflux pump contains the inner membrane H/drug antiporter AcrB comprising three functionally interdependent protomers, cycling consecutively through the loose (L), tight (T) and open (O) state during cooperative catalysis.

Tigecycline efflux in Acinetobacter baumannii is mediated by TetA in synergy with RND-type efflux transporters.

Objectives: To investigate the role of Major Facilitator Superfamily (MFS)-type transporters from Acinetobacter baumannii AYE in tigecycline efflux.

Methods: Two putative tetracycline transporter genes of A. baumannii AYE (tetA and tetG) were heterologously expressed in Escherichia coli and drug susceptibility assays were conducted with tigecycline and three other tetracycline derivatives.

Binding and Transport of Carboxylated Drugs by the Multidrug Transporter AcrB.

AcrAB(Z)-TolC is the main drug efflux transporter complex in Escherichia coli. The extrusion of various toxic compounds depends on several drug binding sites within the trimeric AcrB transporter. Membrane-localized carboxylated substrates, such as fusidic acid and hydrophobic β-lactams, access the pump via a groove between the transmembrane helices TM1 and TM2.

The chloramphenicol/H+ antiporter CraA of Acinetobacter baumannii AYE reveals a broad substrate specificity.

Objectives: To identify major facilitator superfamily (MFS)-type chloramphenicol transporters of Acinetobacter baumannii AYE, to characterize its substrate specificity and identify CraA substrate and H+ binding sites.

Methods: Five ORFs predicted to encode chloramphenicol transporters were heterologously expressed in Escherichia coli and their substrate specificity was determined by drug susceptibility assays on solid agar medium. CraA transport properties were determined via whole cell fluorescence experiments using ethidium and dequalinium.