The Human Breast Cancer Resistance Protein (BCRP/ABCG2) Shows Conformational Changes with Mitoxantrone

Abstract

Summary BCRP/ABCG2 mediates efflux of drugs and xenobiotics. BCRP was expressed in Pichia pastoris, purified to > 90% homogeneity, and subjected to two-dimensional (2-D) crystallization. The 2-D crystals showed a p121 symmetry and projection maps were determined at 5-Å resolution by electron cryomicroscopy. Two crystal forms with and without mitoxantrone were observed with unit cell dimensions of a = 55.4 Å, b = 81.4 Å, γ = 89.8°, and a = 57.3 Å, b =88.0 Å, γ = 89.7°, respectively. The projection map without mitoxantrone revealed an asymmetric structure with ring-shaped density features probably corresponding to a bundle of transmembrane α-helices, and appeared more open and less symmetric than the map with mitroxantrone. The open and closed inward-facing forms of BCRP were generated by homology modeling, representing the substrate-free and substrate-bound conformations in the absence of nucleotide, respectively. These models are consistent with the experimentally observed conformational change upon substrate binding.

Structural determinants of peripheral O-arylcarbamate FAAH inhibitors render them dual substrates for Abcb1 and Abcg2 and restrict their access to the brain

“…While recent structural advances have helped close knowledge gaps about the substrate polyspecificity of ABCB1/Abcb1 [8], the lack of detailed structural information about ABCG2/Abcg2 renders the pharmacophore characterization of its substrates more problematic. Recent attempts to elucidate the substrate-binding properties of ABCG2 have taken advantage of a combination of molecular docking with homology models [9] and mutational analysis [10]. Human ABCG2 and its rodent orthologue Abcg2 recognize a wide range of molecules, including chemotherapeutic agents (e.g.…”

Characterization of native PfABCG protein in Plasmodium falciparum

“…The observed difference between the apparent and calculated molecular masses of PfABCG (65 kDa and 75 kDa) is presently not clear but has been observed with mammalian ABCG proteins. For example, hsABCG1 with a calculated molecular mass of $75kDa has been shown to migrate with an apparent molecular mass of 90kDa [48]; while hsABCG2 was seen to migrate with an apparent molecular mass of 60-65 kDa instead of 72kDa [49,50]. Alternatively PfABCG reactive polypeptide, migrating with a molecular mass of 65 kDa, may be a cross-reacting protein different from PfABCG.…”

Pyrimido[1″,2″:1,5]pyrazolo[3,4-b]quinolines: Novel compounds that reverse ABCG2-mediated resistance in cancer cells

“…A homology model of ABCG2 [24], using mouse apoprotein (PDB ID: 3G5U) [25] was utilized as a template for the molecular docking studies. The homology model of ABCG2 was optimized using the 'Protein Preparation Wizard' workflow implemented in the Schrödinger molecular modeling suite (Schrödinger, Inc., New York, NY, 2012).…”