title: Location of contact residues in pharmacologically distinct drug binding sites on P-glycoprotein.
abstract: The multidrug resistance P-glycoprotein (P-gp) is characterised by the ability to bind and/or transport an astonishing array of drugs. This poly-specificity is imparted by at least four pharmacologically distinct binding sites within the transmembrane domain. Whether or not these sites are spatially distinct has remained unclear. Biochemical and structural investigations have implicated a central cavity as the likely location for the binding sites. In the present investigation, a number of contact residues that are involved in drug binding were identified through biochemical assays using purified, reconstituted P-gp. Drugs were selected to represent each of the four pharmacologically distinct sites. Contact residues important in rhodamine123 binding were identified in the central cavity of P-gp. However, contact residues for the binding of vinblastine, paclitaxel and nicardipine were located at the lipid-protein interface rather than the central cavity. A key residue (F978) within the central cavity is believed to be involved in coupling drug binding to nucleotide hydrolysis. Data observed in this investigation suggest the presence of spatially distinct drug binding sites connecting through to a single translocation pore in the central cavity.
authors.affiliation: Division of Biomedical Science & Biochemistry, Research School of Biology and Medical School, The Australian National University, Canberra, Australia.
authors.forename: Rituparna
authors.initials: R
authors.lastname: Mittra
authors.affiliation: Division of Biomedical Science & Biochemistry, Research School of Biology and Medical School, The Australian National University, Canberra, Australia.
authors.forename: Megan
authors.initials: M
authors.lastname: Pavy
authors.affiliation: Research School of Chemistry, The Australian National University, Canberra, Australia.
authors.forename: Nanditha
authors.initials: N
authors.lastname: Subramanian
authors.affiliation: School of Life Sciences, University of Technology Sydney, Australia.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: George
authors.affiliation: Research School of Chemistry, The Australian National University, Canberra, Australia.
authors.forename: Megan L
authors.initials: ML
authors.lastname: O'Mara
authors.affiliation: School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, UK.
authors.forename: Ian D
authors.initials: ID
authors.lastname: Kerr
authors.affiliation: Division of Biomedical Science & Biochemistry, Research School of Biology and Medical School, The Australian National University, Canberra, Australia. Electronic address: richard.callaghan@anu.edu.au.
authors.forename: Richard
authors.initials: R
authors.lastname: Callaghan
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009036:Moths; D016297:Mutagenesis, Site-Directed; D009529:Nicardipine / Q000378:metabolism; D017239:Paclitaxel / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020112:Rhodamine 123 / Q000378:metabolism; D014747:Vinblastine / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003470:Culture Media; D020033:Protein Isoforms; D020112:Rhodamine 123; D014747:Vinblastine; D009529:Nicardipine; D017239:Paclitaxel
keywords: ABC protein; Adenosine triphosphate (PubMed CID: 5957); Cancer chemotherapy; Membrane transport; Multidrug resistance; Nicardipine hydrochloride (PubMed CID: 41114); P-glycoprotein; Paclitaxel (PubMed CID: 36314); Rhodamine123 (PubMed CID: 9929799); Vinblastine sulphate (PubMed CID: 5388983)