Is ATP binding responsible for initiating drug translocation by the multidrug transporter ABCG2

• Published in: The FEBS journal 2008-09, Vol.275 (17), p.4354-4362
• Main Authors: McDevitt, Christopher A, Crowley, Emily, Hobbs, Gemma, Starr, Kate J, Kerr, Ian D, Callaghan, Richard
• Format: Article
• Language: English
• Subjects: ABC transporter; Adenosine triphosphatase; Adenosine Triphosphate - metabolism; Animals; Antineoplastic Agents - metabolism; Antineoplastic Agents - pharmacokinetics; ATP Binding Cassette Transporter, Sub-Family G, Member 2; ATP-Binding Cassette Transporters - physiology; Binding sites; Biochemistry; Cancer; Cell Line; Chemotherapy; Daunorubicin - metabolism; Daunorubicin - pharmacokinetics; Drug resistance; membrane protein; Moths; multidrug‐resistance; Neoplasm Proteins - physiology; power‐stroke; Protein Binding; Radioligand Assay; Tritium
• ISSN: 1742-464X; 1742-4658
• DOI: 10.1111/j.1742-4658.2008.06578.x

ABCG2 confers resistance to cancer cells by mediating the ATP-dependent outward efflux of chemotherapeutic compounds. Recent studies have indicated that the protein contains a number of interconnected drug binding sites. The present investigation examines the coupling of drug binding to ATP hydrolysis. Initial drug binding to the protein requires a high-affinity interaction with the drug binding site, followed by transition and reorientation to the low-affinity state to enable dissociation at the extracellular face. [³H]Daunomycin binding to the ABCG2R⁴⁸²G isoform was examined in the nucleotide-bound and post-hydrolytic conformations. Binding of [³H]daunomycin was displaced by ATP analogues, indicating transition to a low-affinity conformation prior to hydrolysis. The low-affinity state was observed to be retained immediately post-hydrolysis. Therefore, the dissociation of phosphate and/or ADP is likely to be responsible for resetting of the transporter. The data indicate that, like ABCB1 and ABCC1, the 'power stroke' for translocation in ABCG2R⁴⁸²G is the binding of nucleotide.