{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,30]],"date-time":"2026-09-30T01:02:58Z","timestamp":1790730178023,"version":"4.1.0"},"reference-count":50,"publisher":"Portland Press Ltd.","issue":"2","content-domain":{"domain":["portlandpress.com"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2006,10,15]]},"abstract":"<jats:p>The Pgp (P-glycoprotein) multidrug transporter couples ATP hydrolysis at two cytoplasmic NBDs (nucleotide-binding domains) to the transport of hydrophobic compounds. Orthovanadate (Vi) and fluoroaluminate (AlFx) trap nucleotide in one NBD by forming stable catalytically inactive complexes (Pgp\u2013M2+\u2013ADP\u2013X), which are proposed to resemble the catalytic transition state, whereas the complex formed by beryllium fluoride (BeFx) is proposed to resemble the ground state. We studied the trapped complexes formed via incubation of Pgp with ATP (catalytically forward) or ADP (reverse) and Vi, BeFx or AlFx using Mg2+ or Co2+ as the bivalent cation. Quenching of intrinsic Pgp tryptophan fluorescence by acrylamide, iodide and caesium indicated that conformational changes took place upon formation of the trapped complexes. Trapping with Vi and ATP led to a 6-fold increase in the acrylamide quenching constant, KSV, suggesting that large conformational changes take place in the Pgp transmembrane regions on trapping in the forward direction. Trapping with Vi and ADP gave only a small change in quenching, indicating that the forward- and reverse-trapped complexes are different. TNP (trinitrophenyl)\u2013ATP\/TNP\u2013ADP interacted with all of the trapped complexes, however, the fluorescence enhancement differed for the trapped states, suggesting a change in polarity in the nucleotide-binding sites. The nucleotide-binding site of the BeFx-trapped complex was much more polar than that of the Vi and AlFx complexes. Functionally, all the trapped complexes were able to bind drugs and TNP\u2013nucleotides with unchanged affinity compared with native Pgp.<\/jats:p>","DOI":"10.1042\/bj20060015","type":"journal-article","created":{"date-parts":[[2006,10,2]],"date-time":"2006-10-02T14:23:22Z","timestamp":1159799002000},"page":"315-323","update-policy":"https:\/\/doi.org\/10.1042\/crossmark_policy","source":"Crossref","is-referenced-by-count":34,"title":["Conformational and functional characterization of trapped complexes of the P-glycoprotein multidrug transporter"],"prefix":"10.1042","volume":"399","author":[{"given":"Paula\u00a0L.","family":"Russell","sequence":"first","affiliation":[{"name":"Department of Molecular and Cellular Biology University of Guelph, Guelph, ON, Canada N1G 2W1"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Frances\u00a0J.","family":"Sharom","sequence":"additional","affiliation":[{"name":"Department of Molecular and Cellular Biology University of Guelph, Guelph, ON, Canada N1G 2W1"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"288","published-online":{"date-parts":[[2006,9,27]]},"reference":[{"key":"2021112217510103000_B1","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1016\/B978-012352551-2\/50002-0","article-title":"Phylogenetic and functional classification of ABC (ATP-binding cassette) systems","volume-title":"ABC Proteins: from Bacteria to Man","author":"Dassa","year":"2003"},{"key":"2021112217510103000_B2","doi-asserted-by":"crossref","first-page":"537","DOI":"10.1146\/annurev.biochem.71.102301.093055","article-title":"Mammalian ABC transporters in health and disease","volume":"71","author":"Borst","year":"2002","journal-title":"Annu. 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