ATP-Binding Cassette Transporter Structure Changes Detected by Intramolecular Fluorescence Energy Transfer for High-Throughput Screening

Mol Pharmacol. 2015 Jul;88(1):84-94. doi: 10.1124/mol.114.096792. Epub 2015 Apr 29.


Multidrug resistance protein 1 (MRP1) actively transports a wide variety of drugs out of cells. To quantify MRP1 structural dynamics, we engineered a "two-color MRP1" construct by fusing green fluorescent protein (GFP) and TagRFP to MRP1 nucleotide-binding domains NBD1 and NBD2, respectively. The recombinant MRP1 protein expressed and trafficked normally to the plasma membrane. Two-color MRP1 transport activity was normal, as shown by vesicular transport of [(3)H]17β-estradiol-17-β-(D-glucuronide) and doxorubicin efflux in AAV-293 cells. We quantified fluorescence resonance energy transfer (FRET) from GFP to TagRFP as an index of NBD conformational changes. Our results show that ATP binding induces a large-amplitude conformational change that brings the NBDs into closer proximity. FRET was further increased by substrate in the presence of ATP but not by substrate alone. The data suggest that substrate binding is required to achieve a fully closed and compact structure. ATP analogs bind MRP1 with reduced apparent affinity, inducing a partially closed conformation. The results demonstrate the utility of the two-color MRP1 construct for investigating ATP-binding cassette transporter structural dynamics, and it holds great promise for high-throughput screening of chemical libraries for unknown activators, inhibitors, or transportable substrates of MRP1.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B / chemistry
  • ATP Binding Cassette Transporter, Subfamily B / metabolism
  • Adenosine Triphosphate / metabolism*
  • Binding Sites
  • Cell Membrane / metabolism
  • Drug Discovery
  • Fluorescence Resonance Energy Transfer / methods*
  • Green Fluorescent Proteins / chemistry
  • Green Fluorescent Proteins / metabolism
  • HEK293 Cells
  • High-Throughput Screening Assays / methods
  • Humans
  • Models, Molecular
  • Protein Structure, Secondary
  • Small Molecule Libraries / metabolism*
  • Small Molecule Libraries / pharmacology


  • ABCB1 protein, human
  • ATP Binding Cassette Transporter, Subfamily B
  • Small Molecule Libraries
  • Green Fluorescent Proteins
  • Adenosine Triphosphate