Structure, orientation, and conformational changes in transmembrane domains of multidrug transporters.

Multidrug transporter proteins promote the active transmembrane efflux of noxious drugs, thereby decreasing their accumulation in the intracellular medium and reducing their therapeutic efficiency. Expression of such proteins drastically reduces the efficiency of chemotherapeutic treatments against cancer and various infectious diseases. To overcome major difficulties related to the crystallization of membrane proteins, other experimental approaches have been developed to gain information on the structural changes involved in drug transport.

The precursor of a psychrophilic alpha-amylase: structural characterization and insights into cold adaptation.

The alpha-amylase precursor from the bacterium Pseudoalteromonas haloplanktis possesses a propeptide at the C-terminus possibly responsible for outer membrane translocation. Unlike the predicted beta-barrel of autotransporters, this C-terminal propeptide displays a noticeable alpha-helix content. It is connected to the enzyme by a disordered linker and has no significant interaction with the catalytic domain.

A new experimental approach to detect long-range conformational changes transmitted between the membrane and cytosolic domains of LmrA, a bacterial multidrug transporter.

LmrA confers multidrug resistance to Lactococcus lactis by mediating the extrusion of antibiotics, out of the bacterial membrane, using the energy derived from ATP hydrolysis. Cooperation between the cytosolic and membrane-embedded domains plays a crucial role in regulating the transport ATPase cycle of this protein. In order to demonstrate the existence of a structural coupling required for the cross-talk between drug transport and ATP hydrolysis, we studied specifically the dynamic changes occurring in the membrane-embedded and cytosolic domains of LmrA by combining infrared linear dichroic spectrum measurements in the course of H/D exchange with Trp fluorescence quenching by a water-soluble attenuator.

Structural and functional asymmetry of the nucleotide-binding domains of P-glycoprotein investigated by attenuated total reflection Fourier transform infrared spectroscopy.

The dynamic changes occurring during the catalytic cycle of MDR3 P-glycoprotein (Pgp) and the role of each nucleotide-binding domain (NBD) in the transport process were investigated using attenuated total reflection Fourier transform infrared spectroscopy. For this purpose, wild-type Pgp and two mutations of homologous residues in each NBD were studied. On the one hand, we demonstrate here that, during its catalytic cycle, Pgp does not undergo secondary structure changes, but only modifications in its stability and accessibility to the external environment.