RT Journal Article
SR Electronic
T1 An Outward-facing Aromatic Amino Acid is Crucial for Signalling Between the Membrane Spanning and Nucleotide Binding Domains of Multidrug Resistance Protein 1 (MRP1; ABCC1)
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.118.112615
DO 10.1124/mol.118.112615
A1 Kevin E. Weigl
A1 Gwenaelle Conseil
A1 Alice J. Rothnie
A1 May Arama
A1 Yossi Tsfadia
A1 Susan P.C. Cole
YR 2018
UL http://molpharm.aspetjournals.org/content/early/2018/07/05/mol.118.112615.abstract
AB The 190 kDa human MRP1 is an ATP-binding cassette multidrug and multiorganic anion efflux transporter. The 17 transmembrane helices of its three membrane spanning domains, together with its two nucleotide binding domains (NBDs), form a stabilizing network of domain-domain interactions that ensure substrate binding in the cytoplasm is efficiently coupled to ATP binding and hydrolysis to effect solute efflux into the extracellular milieu. Here we show that Ala substitution of Phe583 in an outward-facing loop between the two halves of the transporter essentially eliminated binding of multiple organic anions by MRP1. Conservative substitutions with Trp and Tyr had little or no effect. The F583A mutation also caused a substantial increase in orthovanadate-induced trapping of azidoADP by the cytoplasmic NBDs of MRP1, although binding of ATP was unaffected. These observations indicate that the loss of the aromatic side chain at position 583 impairs release of ADP and thus effectively locks the transporter in a low affinity solute binding state. Phe583 is the first outward-facing amino acid in MRP1 found to be critical for its transport function. Our data provides evidence for long-range coupling, presumably via allosteric interaction, between this outward-facing region of MRP1 and both the solute binding and nucleotide binding regions of the transporter. Cryoelectron microscopy structural and homology models of MRP1 indicate that the orientation of the Phe583 side-chain is altered by ATP binding but are currently unable to provide insights into the molecular mechanism by which this long-range signalling is propagated.