Powering the ABC multidrug exporter LmrA: How nucleotides embrace the ion-motive force.

LmrA is a bacterial ATP-binding cassette (ABC) multidrug exporter that uses metabolic energy to transport ions, cytotoxic drugs, and lipids. Voltage clamping in a Port-a-Patch was used to monitor electrical currents associated with the transport of monovalent cationic HEPES by single-LmrA transporters and ensembles of transporters. In these experiments, one proton and one chloride ion are effluxed together with each HEPES ion out of the inner compartment, whereas two sodium ions are transported into this compartment.

A multidrug ABC transporter with a taste for salt.

Background: LmrA is a multidrug ATP-binding cassette (ABC) transporter from Lactococcus lactis with no known physiological substrate, which can transport a wide range of chemotherapeutic agents and toxins from the cell. The protein can functionally replace the human homologue ABCB1 (also termed multidrug resistance P-glycoprotein MDR1) in lung fibroblast cells. Even though LmrA mediates ATP-dependent transport, it can use the proton-motive force to transport substrates, such as ethidium bromide, across the membrane by a reversible, H(+)-dependent, secondary-active transport reaction.

Developmental expression of Commd1 in the liver of the Jackson toxic milk mouse.

Wilson disease (WD) is due to mutations in ATP7B, which encodes an intracellular metal-transporting P-type ATPase. In WD holoceruloplasmin production and biliary excretion of copper are decreased, leading to copper overload, oxidative stress and apoptotic cell death. Other copper-binding proteins include COMMD1, which is inactive in the Bedlington terrier hereditary copper toxicosis, and XIAP, which regulates apoptosis.