a multidrug abc transporter with a taste for salt多种abc转运蛋白和盐的味道.pdfVIP

A Multidrug ABC Transporter with a Taste for Salt 1. 1. 1 1 2 Saroj Velamakanni , Calvin H. F. Lau , Daniel A. P. Gutmann , Henrietta Venter , Nelson P. Barrera , 1 1 2 1 1 Markus A. Seeger , Barbara Woebking , Dijana Matak-Vinkovic , Lekshmy Balakrishnan , Yao Yao , 1 1 2 1¤ 1 Edmond C. Y. U , Richard A. Shilling , Carol V. Robinson , Peter Thorn , Hendrik W. van Veen * 1 Department of Pharmacology, University of Cambridge, Cambridge, United Kingdom, 2 Department of Chemistry, University of Cambridge, Cambridge, United Kingdom Abstract 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. The mechanism and physiological context of this reaction are not known. Methodology/Principal Findings: We examined ion transport by LmrA in electrophysiological experiments and in transport studies usin