Download MendeleyMolecular basis of cholesterol efflux via ABCG subfamily transporters.
Sun, Y., Wang, J., Long, T., Qi, X., Donnelly, L., Elghobashi-Meinhardt, N., Esparza, L., Cohen, J.C., Xie, X.S., Hobbs, H.H., Li, X.(2021) Proc Natl Acad Sci U S A 118
- PubMed: 34404721
- DOI: https://doi.org/10.1073/pnas.2110483118
- Primary Citation of Related Structures:
7R87, 7R88, 7R89, 7R8A, 7R8B, 7R8C, 7R8D, 7R8E - PubMed Abstract:
The ABCG1 homodimer (G1) and ABCG5-ABCG8 heterodimer (G5G8), two members of the adenosine triphosphate (ATP)-binding cassette (ABC) transporter G family, are required for maintenance of cellular cholesterol levels. G5G8 mediates secretion of neutral sterols into bile and the gut lumen, whereas G1 transports cholesterol from macrophages to high-density lipoproteins (HDLs). The mechanisms used by G5G8 and G1 to recognize and export sterols remain unclear. Here, we report cryoelectron microscopy (cryo-EM) structures of human G5G8 in sterol-bound and human G1 in cholesterol- and ATP-bound states. Both transporters have a sterol-binding site that is accessible from the cytosolic leaflet. A second site is present midway through the transmembrane domains of G5G8. The Walker A motif of G8 adopts a unique conformation that accounts for the marked asymmetry in ATPase activities between the two nucleotide-binding sites of G5G8. These structures, along with functional validation studies, provide a mechanistic framework for understanding cholesterol efflux via ABC transporters.
Organizational Affiliation:
Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390.
