Extracellular mutation induces an allosteric effect across the membrane and hampers the activity of MRP1 (ABCC1)

Dynamic conformational changes play a major role in the function of proteins, including the ATP-Binding Cassette (ABC) transporters. Multidrug Resistance Protein 1 (MRP1) is an ABC exporter that protects cells from toxic molecules. Overexpression of MRP1 has been shown to confer Multidrug Resistance (MDR), a phenomenon in which cancer cells are capable to defend themselves against a broad variety of drugs. In this study, we used varied computational techniques to explore the unique F583A mutation that is known to essentially lock the transporter in a low-affinity solute binding state. We demonstrate how macro-scale conformational changes affect MRP1's stability and dynamics, and how these changes correspond to micro-scale structural perturbations in helices 10-11 and the nucleotide-binding domains (NBDs) of the protein in regions known to be crucial for its ATPase activity. We demonstrate how a single substitution of an outward-facing aromatic amino acid causes a long-range allosteric effect that propagates across the membrane, ranging from the extracellular ECL5 loop to the cytoplasmic NBD2 over a distance of nearly 75 Å, leaving the protein in a non-functional state, and provide the putative allosteric pathway. The identified allosteric structural pathway is not only in agreement with experimental data but enhances our mechanical understanding of MRP1, thereby facilitating the rational design of chemosensitizers toward the success of chemotherapy treatments.