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J Biol Chem ; 278(14): 11995-9, 2003 Apr 04.
Article in English | MEDLINE | ID: mdl-12551908

ABSTRACT

Pdr5p, the major multidrug exporter in Saccharomyces cerevisiae, is a member of the ATP-binding cassette (ABC) superfamily. Pdr5p shares similar mechanisms of substrate recognition and transport with the human MDR1-Pgp, despite an inverted topology of transmembrane and ATP-binding domains. The hexahistidine-tagged Pdr5p multidrug transporter was highly overexpressed in yeast strains where other ABC genes have been deleted. After solubilization and purification, the 160-kDa recombinant Pdr5p has been reconstituted into a lipid bilayer. Controlled detergent removal from Pdr5p-lipid-detergent micelles allowed the production of peculiar square-shaped particles coexisting with liposomes and proteoliposomes. These particles having 11 nm in side were well suited for single particle analysis by electron microscopy. From such analysis, a computed volume has been determined at 25-A resolution, giving insight into the structural organization of Pdr5p. Comparison with the reported structures of different bacterial ABC transporters was consistent with a dimeric organization of Pdr5p in the square particles. Each monomer was composed of three subregions corresponding to a membrane region of about 50 A in height that joins two well separated protruding stalks of about 40 A in height, ending each one with a cytoplasmic nucleotide-binding domain (NBD) lobe of about 50-60 A in diameter. The three-dimensional reconstruction of Pdr5p revealed a close arrangement and a structural asymmetric organization of the two NBDs that appeared oriented perpendicularly within a monomer. The existence of different angular positions of the NBDs, with respect to the stalks, suggest rotational movements during the catalytic cycle.


Subject(s)
ATP-Binding Cassette Transporters/chemistry , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae/chemistry , ATP-Binding Cassette Transporters/genetics , ATP-Binding Cassette Transporters/ultrastructure , Cell Membrane/physiology , Crystallography, X-Ray , Drug Resistance, Multiple , Microscopy, Electron , Protein Structure, Quaternary , Protein Structure, Tertiary , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/ultrastructure
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