abcg5g8-crystallization-lipidic-bicelle-environment-for-x-ray

ABCG5/G8 Crystallization in a Lipidic Bicelle Environment for X-Ray Crystallography

ATP-binding cassette (ABC) transporters constitute lipid-embedded membrane proteins. Extracting these membrane proteins from the lipid bilayer to an ...

University of Ottawa

Lipid composition in cellular membranes plays an important role in maintaining the structural integrity of cells and in regulating cellular signaling that controls functions of both membrane-anchored and cytoplasmic proteins. ATP-dependent ABC and P4-ATPase lipid transporters, two integral membrane proteins, are known to contribute to lipid translocation across the lipid bilayers on the cellular membranes. In this review, we will highlight current knowledge about the role of cholesterol and phospholipids of cellular membranes in regulating cell signaling and how lipid transporters participate this process.

Lipid Transporters Beam Signals from Cell Membranes.

The ATP-binding cassette (ABC) sterol transporters are responsible for maintaining cholesterol homeostasis in mammals by participating in reverse cholesterol transport (RCT) or transintestinal cholesterol efflux (TICE). The heterodimeric ABCG5/G8 carries out selective sterol excretion, preventing the abnormal accumulation of plant sterols in human bodies, while homodimeric ABCG1 contributes to the biogenesis and metabolism of high-density lipoproteins. A sterol-binding site on ABCG5/G8 was proposed at the interface of the transmembrane domain and the core of lipid bilayers. In this study, we have determined the crystal structure of ABCG5/G8 in a cholesterol-bound state. The structure combined with amino acid sequence analysis shows that in the proximity of the sterol-binding site, a highly conserved phenylalanine array supports functional implications for ABCG cholesterol/sterol transporters. Lastly, in silico docking analysis of cholesterol and stigmasterol (a plant sterol) suggests sterol-binding selectivity on ABCG5/G8, but not ABCG1. Together, our results provide a structural basis for cholesterol binding on ABCG5/G8 and the sterol selectivity by ABCG transporters.

Structural Analysis of Cholesterol Binding and Sterol Selectivity by ABCG5/G8.

ATP-Binding cassette subfamily G (ABCG) sterol transporters maintain whole body endogenous and exogenous sterol homeostasis. A substantial portion of exogenous sterols are undigestible phytosterols (plant sterols), which can introduce complications when accumulated. ABCG5/G8 is the main protein functioning to remove ingested plant sterols providing protection from their toxic effects, although, the structural features behind substrate binding in ABCG5/G8 remain poorly resolved. Within this data article, we present extended preceding in the determination of the cholesterol-bound crystal structure and the sterol docking analysis. The crystal structure was deposited in the Protein Data Bank with the accession number of 8CUB, whereas the diffraction images were deposited at the SBGrid Data Bank. This dataset follows the research article entitled as "Structural analysis of cholesterol binding and sterol selectivity by ABCG5/G8" (doi: 10.1016/j.jmb.2022.167795).

Data on structural analysis of cholesterol binding and sterol selectivity by ABCG5/G8.

The subfamily-G ATP-binding cassette (ABCG) transporters play important roles in regulating cholesterol homeostasis. Recent progress in the structural data of ABCG1 and ABCG5/G8 disclose putative sterol binding sites that suggest the possible cholesterol translocation pathway. ABCG1 and ABCG5/G8 share high similarity in the overall molecular architecture, and both transporters appear to use several unique structural motifs to facilitate cholesterol transport along this pathway, including the phenylalanine highway and the hydrophobic valve. Interestingly, ABCG5/G8 is known to transport cholesterol and phytosterols, whereas ABCG1 seems to exclusively transport cholesterol. Ligand docking analysis indeed suggests a difference in recruiting sterol molecules to the known sterol-binding sites. Here, we further discuss how the different and shared structural features are relevant to their physiological functions, and finally provide our perspective on future studies in ABCG cholesterol transporters.

Danny Farhat

Department of Biochemistry,
Microbiology and Immunology,
Faculty of Medicine,
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine

University of Ottawa

ABCG5/G8 Crystallization in a Lipidic Bicelle Environment for X-Ray Crystallography

Danny Farhat

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Biochemistry,Microbiology and Immunology,Faculty of Medicine,Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine

University of Ottawa

ABCG5/G8 Crystallization in a Lipidic Bicelle Environment for X-Ray Crystallography

Department of Biochemistry,
Microbiology and Immunology,
Faculty of Medicine,
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine